Trilobite “horns” may have been used as weapons in male-male combat

January 19, 2023 • 9:15 am

Years ago I met Richard Fortey at the inaugural meeting of Spain’s new evolution society, and found him an affable and lovely guy. He’s a paleontologist and writer, and I had the pleasure of reading and giving a positive review to his first book, Life: A Natural History of the first Four Billion Years on Earth, which is well worth reading (he’s written several other books, including Trilobite: Eyewitness to Evolution (also a good read).

And it’s four trilobite species that are the subject of Fortey’s new paper coauthored with Alan D. Gishlick, a geophysical sciences professor at Bloomsburg University, in PNAS, a paper you can read for free by clicking the title below (it’s free with the legal Unpaywall app., the pdf is here, the reference is at bottom, and judicious inquiry might yield a pdf if you can’t see the paper). Trilobites are common fossils, and were marine arthropods that went extinct without leaving descendants.

The upshot is that Gishlick and Fortey analyzed fossils of one species of trilobite found in Morocco, deriving from the Devonian (400 million years ago). This species, Walliserops trifurcatus, had a long trident attached to the front of their bodies, and tried to figure out what it was for. They also found one adult individual whose trident was a bit deformed (see below). Their conclusion is that these were weapons used by males to fight with other males, almost surely to compete for females. They are, posit the authors, the arthropod equivalent of reindeer horns. The other possible functions (feeding, digging, etc.) were largely ruled out.

Read on:

Here are four species of Walliserops, shown below. All specimens bear a rigid cephalic trident. W. trifurcatus has a slightly recurved trident that bends upwards, while the other species have tridents more flush with the surface of the sediment (all captions come from the paper):

Four recognized species of *Walliserops*: A. *trifurcatus*, UA 13447 (topotype); B. *hammi*, UA 13446 (holotype); C. *tridens* UA 13451 (holotype); D. *lindoei* ROMIP 56997. Images taken from photogrammetric models. (Scale bar, 10 mm.)

The obvious question is: what is this damn thing for? And there are several hypotheses, all assuming that the structure was molded by natural selection (which includes sexual selection). The authors find evidence against all but one possible function. Here are the alternatives (of course, it could have been used for several things, but it’s likely that selection was wholly or largely on one function). Indented bits are quotes from the paper. The rest of the discussion concerns W. trifurcatus:

A.) Defense. Perhaps the structure could have been used to ward off predators, like the spines found on other trilobites. Here’s how the authors rule this out:

However, such a function would have been difficult given the overall anatomy of the trident and the trilobite. The trident is rigidly attached and cannot be moved independently from the cephalon; it could only be flexed in a dorsal-ventral plane by the trilobite raising and lowering its cephalon. This would create further difficulties since the long genal spines limit how high the head could be angled without lifting the entire body. The trident, therefore, could not be employed in a versatile way, nor be presented as to defend from a predator attacking from above or behind. This morphology is not consistent with a defensive structure.

B.) A feeding structure. Doesn’t seem likely:

A second possible function for the trident would be as an aid to feeding. Like all members of the Phacopida, Walliserops was probably a scavenger/predator, and it might be considered as a possibility that the trident was a comparatively sophisticated sensory device concerned with early detection of prey species—such as buried annelid worms—which could then be grasped by the endopods of the ventral limbs.

C.) Sensory detection of the environment. This is also deemed unlikely from inspection of the structure:

However, examination of the trident in optical and scanning electron microscopy failed to find the arrays of cuticular pits or tubercles usually indicative of the presence of sensilla in fossil arthropods. Most groups of trilobites include species with exterior exoskeletal pitting that is preserved even if the intracuticular canals have been removed by calcite reorganization—and there is no evidence of such exterior pitting on the trident of Walliserops. The absence of evidence for specialized organs on the tines makes it unlikely that it was primarily a sensory apparatus.

D.) A spear to pierce prey: Unlikely because the structure was inflexible, so the animal would have no way of accessing speared prey.

E.) An apparatus to dig, perhaps for prey. The way it’s shaped and angled seems to preclude this (remember, it’s slightly recurved upward; see below):

Another possibility is that the trident may have been used to agitate sediment to disturb prey items, which could then be trapped by the limbs. It is difficult to conceive of W. trifurcatus digging into sediment because to engage sufficiently with the substrate the cephalon would have to tilt at an angle greater than would be allowed by movement on the posterior occipital margin. Equally, if the thorax was arched, the pygidial spines themselves would dig into the sediment.

F.) A combat device on males molded by sexual selection mediated by male-male competition for mates. The authors consider this most likely, especially because the tridents resemble the structure of male dynastine (rhinoceros) beetles, which use them to fight for females.

Here’s a picture of three of those beetles which have similar projections as do the Walliserops trilobites (the one at the extreme right).

The authors did a complex morphometric analysis of body and horn shape of W. trifurcatus, comparing it with living rhinoceros beetles to see if the trident could have been used for shoveling/prying, grasping, or fencing—the three types of male-male combat seen in living beetles. The analysis puts the trilobite in the group of living rhinoceros beetles whose males fight by fencing/shoveling: jousting with the structure in front and then trying to shovel the opponent over onto its back. I won’t go into the gory statistical details, which involve principal-components analysis, but the recurved structure of the trilobite’s “trident” is similar to that of shoveling, prying, and fencing beetles (left column: observed means of fighting of living beetles; center: the cephalic structures used; right: the species name [trilobite at the bottom]).

Cephalic structures of taxa treated in this research in lateral view showing the nature of the curvature and orientation of the tip of the active weapon and how it relates to its employment in combat.

As you see, and as the statistical groupings show, W. trifurcatus is similar to the structures used in rhinoceros beetles for fencing, prying and shoveling. Here is Gishlick and Fortey’s scenario of how the males battled it out in the competition to pass on their genes:

We would hypothesize a fighting scenario in Walliserops similar to that of Trypoxylus. The trilobites would meet and at first spar with their forks, pushing and poking. At some point, they would shift to trying to slide the fork under the other, in an attempt to flip them over. Given the morphology of Walliserops, flipping would be a very effective combat technique. Although the appendages of Walliserops are unknown, it is likely that they were like those of other phacopids in not extending beyond the carapace. This is seen in the Devonian Chotecops, asteropygines Asteropyge, and Rhenops, and recently described in three-dimensional material from the Silurian Dalmanites. Once the trilobite was inverted, righting would not be a simple matter, especially if the dorsally directed spines had snagged in the sediment. An upended trilobite would probably be even more helpless than a beetle in this position and thus excluded from sexual competition.

It might also be dead!

Now the first thing that struck me when I saw this paper was the question that would have occurred to many of you: WHERE ARE THE BLOODY FEMALES?? One of the signs of male-male competition is that the structures used to compete are present in males but almost never in females, as they’re of no use in that sex—and detrimental to fitness if you don’t use them. Male deer have antlers, females do not. Body size, used for combat in elephant seals, is huge in the males, and much, much smaller in females. So if these trilobite horns really were tools used for the “combat” form of sexual selection (the other form, as pointed out by Darwin, is female preference), the females should be around but lack the ornaments. Where are they?

Gislick and Fortey suggest that the females were indeed around, but because they lack the tridents they have not been identified as females of Walliserops trifurcata:

Since the diagnostic synapomorphy [JAC: shared derived trait] for Walliserops is the anterior trident, it would be likely that the female of the species has been classified in a different genus. That leaves two possibilities: either the females of the relevant species are at present unknown, or they are known but placed in another trilobite genus within Asteropyginae.

That mandates a search for trilobites that resemble the males but lack the horns. The authors raise another possibility: the females weren’t preserved or were offstage, living elsewhere, but this seems less likely:

If we extend the beetle analogy further, it is possible that the females are not preserved if some trilobites, like many dynastines, engaged in sex-specific aggregations; in this case, the females were not always present in the same locations as the males, although it is difficult to explain why the latter were selectively caught up in obrution events. [JAC: “Obrution” is rapid burial in the sediments, the way these creatures must have died and been preserved.]

I favor the “females not yet found” hypothesis. There’s one more hypothesis, which is mine: both males and females have tridents. I don’t know why this would be the case, although you could think that it’s used to take other individuals out of action in conspecific competition for food. But that makes little sense.

Finally, the authors found one example of W. trifurcatus with a deformed trident, having an extra spike (a “quadent”?). Here it is on the right. Note that the branching pattern can be asymmetrical in the normal three-pronged structure).

Examples of branching patterns for the middle tines in W. trifurcatus; A. left branching (HMNS 2020-001); B. right branching (HMNS PI 1810); C. teratological example (HMNS PI 1811) showing a secondary branching of the left-branching middle tine. Images taken from photogrammetric models. (Scale bar, 10 mm.)

Because the individual on the right was an adult, Gishlick and Fortey suggest that the deformed structure did not prevent the bearer from growing up and thriving, and thus was unlikely to be used for some vital function like feeding. This adds a little more weight to the sexual-selection hypothesis.

The Upshot: The authors’ analyses and explanations seem plausible to me, though they’d be even stronger if they could find the females. That might be tough: in living species you could find them by looking at mating pairs or even seeing that the DNA was nearly identical, but this isn’t possible with fossilized trilobites, especially because in some living and sexually dimorphic species the females look very different from males. If the authors are right, and I think they are, then this quote from the paper is correct:

Walliserops provides the earliest example in the fossil record of combat behavior, very likely ritualized in competition for mates. Although fossil life habits are difficult to prove, the consilience of morphology, teratology, and biometric data all point to the same interpretation, making it one of the more robust examples of paleoecological speculation.

h/t: Matthew

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Gishlick, A. D. and R. A. Fortey. 2023. Trilobite tridents demonstrate sexual combat 400 Mya. Proc. Nat. Acad. Sci. USA 120 (4) e2119970120 (in press).

Ancient ecosystem reconstructed using fossil DNA

December 9, 2022 • 10:30 am

The oldest DNA sequenced up to now was from a mammoth molar preserved in permafrost, and was dated about 1.2 million years ago. Now a group of scientists, excavating a 100-meter-thick layer of frozen soil in the “polar desert” of northern Greenland, not only found short stretches of DNA that identified the plants, animals, and algae present a long time ago, but also showed that that the time was at least two million years ago.

This is the oldest fossil DNA ever sequenced; it was preserved because it had been adsorbed to minerals in frozen soil. And although the stretches of DNA had degraded into short bits—about 50 base pairs long—they were sufficiently similar to modern taxa that they could identify the groups from which they came. In fact, they could reconstruct the whole ecosystem of that area 2 million years ago. It was much richer in flora and fauna than today’s polar desert, for at that time Greenland wasn’t covered with ice, it was much warmer (mean summer temperature about 10°C), and organisms could migrate to Greenland over land bridges. This might give us a hint of what kind of ecosystem could develop (minus the animals, which are largely gone) should global warming melt the ice presently in Greenland.

You can read the Nature paper for free by clicking on the screenshot below (the pdf is here, reference at the bottom). Below that is a clickable and short popular account of the findings, also published in Nature.

The News article for tyros (short; click to read):

Here’s the location of the area analyzed in northern Greenland, Kap København, where the layer of soil occurred (yellow star). The layer’s presence was already known, and some of the samples had been dug up in 2006 and had been sitting in a Copenhagen freezer for 16 years. Somebody had a bright idea to see if they could identify and sequence the DNA in that soil, and it worked!

(from the paper): a. Location of Kap København Formation in North Greenland at the entrance to the Independence Fjord (82° 24′ N 22° 12′ W) and locations of other Arctic Plio-Pleistocene fossil-bearing sites (red dots). b, Spatial distribution of the erosional remnants of the 100-m thick succession of shallow marine near-shore sediments between Mudderbugt and the low mountains towards the north (a + b refers to location 74a and 74b).

Small stretches of DNA were sequenced and compared to modern DNA as well as DNA inferred in ancestors of modern taxa. The DNA had of course degraded, but they found stretches about 50 base pairs long. Comparisons were mostly to mitochondrial DNA for animals and to conserved chloroplast or other plastid DNA from plants. (They also found ancient pollen that they used in conjunction with the DNA data.)

On the right you can see what animals were found, mostly identified to genus or family because there wasn’t enough DNA to do a finer analysis. I’ll put a list of what they found below this figure:

(from paper): Taxonomic profiles of the animal assemblage from units B1, B2 and B3. Taxa in bold are genera only found as DNA

Here’s what they found from the DNA; these were all organisms living roughly at the same time about 2 million years ago. And remember, that area now harbors very little life.

A mastodon! The figure below shows its placement on the phylogenetic tree of elephants.

70 genera of vascular plants, including sedges, horsetails, willows, hawthorns, spruce, poplars, yew, and birch. Some of these no longer grow in Greenland, but the mixture of plants includes those found in much warmer habitat. See the paper for a full list.

Algae, fungi, and liverworts

Marine phytoplankton and zooplankton

A hare

A caribou-like cervid (caribou are another name for reindeer). How did they get to Greenland? Presumably it wasn’t an island then, but we don’t know for sure.

A bird related to modern geese

A rodent related to modern lemmings

Reef-building coral

An ant

A flea

A horseshoe crab (identified as Limulus polyphemus, the modern horseshoe crab, regarded as a living fossil). These days Limulus doesn’t breed north of the Bay of Fundy (about 45° N), while the location of this site was 82° N. That shows how much warmer it was in Greenland then, though of course the crabs could have evolved in the last several million years to be acclimated to warmer waters.

There were no carnivores found; all the animals were herbivores. That doesn’t mean that there weren’t carnivores there, but I doubt it.

(From paper): b, Phylogenetic placement and pathPhynder62 results of mitochondrial reads uniquely classified to Elephantidae or lower (Source Data 1). Extinct species as identified by either macrofossils or phylogenetic placements are marked with a dagger.

The upshot: Well, we know how that DNA sequences can be preserved for twice as long as we thought, though it has to be under very special circumstances. More important, if you find areas (and they’ll have to be in cold regions) where you can extract even small sequences of fossil DNA, you might be able to reconstruct whole ecosystems. What we’ve found are animals and plants that weren’t expected to be there (reindeer, horseshoe crabs, hawthorns) and so on—species adapted to warmer habitats or now found in areas not in Greenland.

There are two explanations for this: the related today have lost their adaptations to cold habitats when they were forced out of Greenland as the ice caps formed, or the climate was simply warmer. (Of course, both could apply.) But know the latter is surely a contributing factor from independent evidence about climate. Still, there could have been some evolutionary change in thermal tolerance as well, something for which we can’t really get evidence.

But these different explanations aren’t that important: what is important is that we’re able to reconstruct entire ecosystems from fossil DNA—DNA twice as old as previously known. I’ll let the authors have the last word (from the paper):

No single modern plant community or habitat includes the range of taxa represented in many of the macrofossil and DNA samples from Kap København. The community assemblage represents a mixture of modern boreal and Arctic taxa, which has no analogue in modern vegetation. To some degree, this is expected, as the ecological amplitudes of modern members of these genera have been modified by evolution. Furthermore, the combination of the High Arctic photoperiod with warmer conditions and lower atmospheric CO₂ concentrations made the Early Pleistocene climate of North Greenland very different from today. The mixed character of the terrestrial assemblage is also reflected in the marine record, where Arctic and more cosmopolitan SMAGs of Opistokonta and Stramenopila are found together with horseshoe crabs, corals and green microalgae (Archaeplastida), which today inhabit warmer waters at more southern latitudes.

. . . In summary, we show the power of ancient eDNA to add substantial detail to our knowledge of this unique, ancient open boreal forest community intermixed with Arctic species, a community composition that has no modern analogues and included mastodons and reindeer, among others. Similar detailed flora and vertebrate DNA records may survive at other localities. If recovered, these would advance our understanding of the variability of climate and biotic in

Will northern Greenland be like this again should global warming continue? I doubt it, for many of the species, like caribou, can no longer get there, and some, like mastodons, are simply extinct. But it’s enough to know what was there two million years ago.

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Kjær, K.H., Winther Pedersen, M., De Sanctis, B. et al. A 2-million-year-old ecosystem in Greenland uncovered by environmental DNA. Nature 612, 283–291 (2022). https://doi.org/10.1038/s41586-022-05453-y

First fossil evidence for brood care in insects, and a remarkable case of directional asymmetry

July 26, 2022 • 9:45 am

I’ll make this short and sweet. A team of biologists from China have found, examining a fine-grained layer of fossils dated about 164 million years ago, a species of water boatman (“true bugs” in the order Hemiptera) that provide the oldest evidence for parental care in insects. The care is given by females, who attach their eggs to their second pair of legs. The curious thing is that in all the specimens examined, females attach the eggs to only their left middle leg: a rare example of “directional asymmetry”.

You can read about it by clicking below or downloading the pdf here. The reference is at the bottom of the post.

Parental care is not that rare in today’s insects and other arthropods; you can see some examples in modern insects here. It’s also been seen in fossil insects, with the earliest cases described in the paper:

Among Mesozoic insects, the only two direct fossil evidence cases of brooding ethology are provided by the Early Cretaceous cockroach Piniblattella yixianensis with its oothecae enclosing eggs for protection and brood care; and the mid-Cretaceous scale insect Wathondara kotejai, which preserves eggs within a wax ovisac attached to the body of an adult female.

An ootheca is an egg mass, usually enclosed in a hardened shell, as in this modern cockroach (photo below). I assume the mother in the fossil species would stay with the mass, otherwise I can’t see this as an example of “brood care”:

Here’s a picture from Wikipedia labeled “cockroach (Periplaneta americana) with ootheca”:

An “ovisac” is similar: a capsule containing eggs. In the case of the scale insect above, that’s clearly brood care because the ovisac was attached to the body. The Cretaceous period lasted from 145 to 66 million years ago; and oldest of these two insects having brood care dates to about 126 million years ago.

Now, from the Haiffanggou Formation at the Xiayingzi quarry, a formation in NE China with lots of ancient mammals, dinosaurs, and insects, they’ve discovered the water boatman Krataviella popovi. Fu et al examined 157 specimens, 30 of which were females carrying eggs on the middle segment of their LEFT foreleg. Note the directionality of this asymmetry. If it were random, the chance that 30 specimens would all have eggs on the left side would be 9.3 X 10^-10.

The age of this formation is 163.5 million years, so the brood care in these boatmen precedes the previous ‘record’ by about 38 million years. It’s not a unique phenomenon in insects, but it’s the earliest example of that phenomenon.

Here are two photos of females carrying eggs (red arrows), both from the paper and both on their left side. The preservation is remarkable, with some of the specimens prepared using only a sharp knife:

Figure 2 [excerpt]. Brooding in Karataviella popovi. (a) General habitus of egg-carrying specimen (NIGP177390). (b) Details of egg (NIGP177447). (c) General habitus of egg-carrying specimen (NIGP177445). Scale bars: 2 mm in (*a,c,d*); 1 mm in (*f–h*), 500 µm in (*b,e)*

Females and males can be identified independently of egg-carrying, so this is clearly a female trait. Modern water boatmen often attach their eggs directly to the substrate with a kind of biological glue, and then leave, so there is no brood care. The authors hypothesize that the females in these fossil specimens were still using some kind of adhesive, but that it was used this way:

Since water boatmen eggs cannot adhere to new surfaces after being detached from their original place of deposition, this suggests that the females first secreted mucous substance and then laid eggs onto their own left mesotibia by specific bending movements of the abdomen, and then carried the brood until hatching. The unoccupied right mesotibia might have been used to maintain balance when swimming and feeding.

What seems unusual to me is the directionality of the trait: it’s only found on the left middle leg, never the right one. This is called “directional asymmetry”. (If eggs were laid randomly on the left or right legs, it would be called “fluctuating asymmetry”.)

Directional asymmetry has fascinated me because, if it’s an evolved trait, it means that genes producing the directional trait “know” which side of the body they’re on. How can that be? If an ancestor already had biological or genetic gradients from top to bottom and front to back, it still means that a point on the right and left side with equal positions on these other two gradients would experience the same environment. So how do genes determine which side their cells are on so those genes can be activated differentially? I’ve talked about this before, and you can read about it here, here, and here. It’s a fascinating issue that’s not fully resolved. (Of course, once a genetic directional asymmetry is in place, it can be used as a developmental key for the evolution of further asymmetries. We ourselves have a fair number of such asymmetries.)

One solution, which just pushes the question back a bit, is to posit that the females have directionally asymmetrical ovipositors, and it’s simply easier to lay eggs on your left leg than on your right. But if the ovipositors and genitals are symmetrical (the authors don’t say), then it would probably be a directional behavioral asymmetry, with females behaviorally evolved to lay eggs on only one side. I don’t see the advantage of that, but of course behaviors can be directionally asymmetrical and conditioned by genes, like handedness in humans. It’s still interesting to me that one of the earliest cases of directional asymmetry known isn’t discussed by the authors except to mention it. Their own big message is that this is the earliest case of brood care seen in insects, not that it’s directional.

Finally, what is the advantage of evolving this kind of brood care? I’m sure you can think of answers: having your eggs with you protects them from predators, and also aerates the eggs as the beetle moves through the water. Or, as the authors note:

Karataviella adopted a strikingly similar brooding (egg-carrying) strategy to most marine and freshwater shrimps, lobsters and kin (Pleocyemata), where the females attach eggs to their pleopods using a sticky substance, allowing them to actively and intermittently adjust the position of the eggs in water or air, together with the movement during swimming that generates currents, to ensure ventilation and moistening of the eggs. Moreover, in K. popovi and some pleocyematans, a firm but elastic egg stalk is present and may contribute to the aeration of the eggs by facilitating regular shaking motion. Therefore, we speculate that the particular brooding behaviour of K. popovi effectively addresses the problems that large eggs experience relating to hypoxia, drowning and desiccation, resulting in enhanced offspring survival.

To close, here’s a drawing from the paper labeled “Ecological reconstruction of Karataviella popovi and anostracans in the Middle–Late Jurassic Daohugou biota.” What’s weird here is that all the egg masses are shown on the RIGHT mesotibia, and water boatmen do not swim upside down. Go figure.

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Fu. Y. , P. Chen, and D. Huang. 2022. The earliest known brood care in insects. Proc. R. Soc. B.2892022044720220447 http://doi.org/10.1098/rspb.2022.0447

Now it’s paleontology that gets accused of being rotten with structural racism, colonialism, and white supremacy

January 4, 2022 • 11:30 am

One by one, every area of science is falling prey to the “we need to purge ourself of racism” syndrome. It’s in genetics, animal behavior, ecology, chemistry, physics and now, at least for the first time I’ve seen, in paleontology. It wouldn’t be so bad if I really thought that all the fields of science are permeated with hatred and bigotry at present, but I just don’t see that. There are accusations, but rarely do we get evidence. (See the Sci Am article on E. O. Wilson the other day.)

Of course in the bad old days, when racism and misogyny were acceptable behaviors, yes, many scientists evinced racist and sexist attitudes. And yes, there are still some bigots in science, as there are in every field of endeavor, and we should call out those behaviors and ensure that they’re not common. But the kind of overall accusations of the kind leveled in this article are pure hyperbole, and, to my mind, do more to signal the authors’ virtue than to actually create equal opportunities (not equal outcomes, which are “problematic”) for oppressed people.

To really see the lack of force of accusations of rampant bigotry in STEM, look for surveys, or even examples, of bigotry in papers such as this. They’re notably lacking. The paper below, which just appeared in Paleobiology, has a lot of citations, but a big lacuna when it comes to examples. Perhaps they’re buried in the citations, but no reader is going to trawl through a gazillion citations to find instances of bigotry. And so we’re subject to a long list of accusations, which are virtually identical from field to field. In fact, in many cases you could substitute “chemistry” or “mathematics” for “paleontology” in these papers and then publish it in the discipline -appropriate journal.

The accusations here (yes, some of them are justified, especially the ones about removing fossils without permission or authority) comprise the usual mix—some are justified but exaggerated, and in the end the paper becomes so extreme that it damns the whole field of paleobiology for racism, sexism, colonialism, white supremacy—you name it.

Click on the screenshot to read, and you can find the pdf here(reference at bottom). One of our readers, I believe, said that this is the first time a political/ideological paper had appeared in the journal Paleobiology. I don’t know if that’s true.

The abstract:

There is what is said to be a list of “examples” of “racism and colonialism” in the field, presented in Table 1, but that’s not what Table 1 shows. It’s not a list of examples of biased behavior, but a “glossary of anti-racism terms.” (click to enlarge table).

I have neither the time nor will to look up all the citations to see if they really do show examples of bigotry in paleobiology. But I decided to pick one example and follow it back. That is the one under “erasure”: a reference to a 2016 article in the New York Times Magazine. Paragraph 3, which is the “example” cited, simply says this:

‘‘Erasure’’ refers to the practice of collective indifference that renders certain people and groups invisible. The word migrated out of the academy, where it alluded to the tendency of ideologies to dismiss inconvenient facts, and is increasingly used to describe how inconvenient people are dismissed, their history, pain and achievements blotted out. Compared with words like ‘‘diversity’’ and ‘‘representation,’’ with their glib corporate gloss, ‘‘erasure’’ is a blunt word for a blunt process. It goes beyond simplistic discussions of quotas to ask: Whose stories are taught and told? Whose suffering is recognized? Whose dead are mourned?

It’s a definition, and not, as promised, an example of “the history of racism and colonialism in paleontology since the 1800s. . “. Readers can look up the other references, but my initial foray was not propitious.

Now I’m not going to say that examples are totally absent from this piece. Here, for example are three (the authors count the use of geological methods to extract minerals as oppression in paleobiology):

the forced removal of Navajo and Hopi people from their lands in the Black Mesa in Arizona for access to coal deposits under the guise of a “land dispute” between the Navajo and Hopi (Redhouse Reference Redhouse1985; Cheyfitz Reference Cheyfitz2002; McBride Reference McBride2017);
encroachment upon and threats to the well-being and safety of the Meskwaki, Standing Rock Sioux, and the Cheyenne River Sioux tribes posed by the Dakota Access Pipeline (Noicecat and Spice Reference Noicecat and Spice2016), although a new environmental review is being undertaken as of this writing (Frazin Reference Frazin2020); and
the decision by the federal government to allow the state of Oklahoma to control the environmental regulations over the recently restored autonomous tribal lands of the Five Tribes of Oklahoma (Cherokee, Chickasaw, Choctaw, Creek [Muscogee], and Seminole) to the benefit of the oil and agricultural industries (Chang Reference Chang2020; Environmental Protection Agency 2020).

This does show the continuing disregard of Native Americans, but it reflects more on the perfidy of capitalists and governments than on the racism of paleobiologists themselves.

I’ll finish just by giving some quotations that struck me. Make of them what you will:

Throughout modern history, Western science has directly benefited from the extraction of biological specimens born out of colonialist expansion (Sheets-Pyenson Reference Sheets-Pyenson1986; Roy Reference Roy2018; Chakrabarti Reference Chakrabarti2019; Christison et al. Reference Christison, Tanke and Mallon2020; see also Fagan Reference Fagan2007). These specimens formed the foundations of new theories and subdisciplines of scientific thought (Stix Reference Stix2009), including scientific racism (Curtin Reference Curtin1960).

I presume that the authors know that what happened in the bad old days is being repaired, both by journals requiring documentation of legitimate acquisition of specimens, and countries themselves taking control over their own land and what lies beneath it.

Here we come close to the authors suggestion that we present “other ways of knowing” alongside “Western” wys of knowing in museums. It’s not clear whether they will be presented as having scientific validity:

The incorporation of Indigenous perspectives into museums, which may include views that are antithetical to the narratives previously professed by these institutions, would be a substantial step forward in addressing the colonial history of natural history museums (Vawda Reference Vawda2019). Furthermore, museums can and should be held accountable for cataloging their histories of colonialism and extraction to spur reflection on that history and grow beyond it (Das and Lowe Reference Das and Lowe2018). As part of this effort, the flaws of founders, scientists, and other historic figures involved in the narratives of museums must be publicly recognized for museums to maintain their credibility (Roy Reference Roy2018).

. . . A reflection upon how the history of paleontology is presented in the classroom provides an introduction to the concept of power imbalances in modern academia. In many Western paleontology courses, syllabi ignore how the establishment of paleontology (and geology) in the Americas relied on the removal and erasure of BIPOC groups. In addition to the material presented in the previous sections, examples include Native American beliefs surrounding the biological origins of fossils (Dussias Reference Dussias1996); the first fossils known to Western science in the Americas were identified by enslaved Africans (Mayor Reference Mayor2005); evolutionary theory was grounded in societal and political views regarding race and culture, wherein evolution and extinction were viewed as mechanisms of removing “unfit” species, and was used to justify Western colonialism (Sepkoski Reference Sepkoski2020). Discussing these facts in a science classroom at all ages and education levels may seem inconvenient and unsettling. Students are often taught that science is apolitical, unbiased, and egalitarian, when in reality it is not. Because of this, reality is often supplanted by a racist, colonialist, and inherently misleading narrative (Sabbagh Reference Sabbagh2017).

We see that, in all these interpretations, the field and the way it’s taught is asked to change dramatically, from an instructional presentation of scientific truth to a form of social engineering designed to indict practitioners in the field in the past, and to validate “indigenous” views of science that are invalid. Science class, as in all of these manifestos, will change from people learning the truths uncovered by paleobiology into a discussion of the bigotry, racism, and sexism of paleobiologists themselves. Doesn’t this belong in a “studies” course or a “history of science” course?

I’m starting to think that the purpose of these attacks is not just to indict everyone for bigotry and white supremacy, but to fundamentally change the nature of science. It is no longer an objective search for truth (yes, of course some scientists are biased), but just one more tool to achieve not just equality but equity. If anything is being “erased,” it’s the distinction between the sciences and the humanities. “Science” is to become “science studies.”

Examples:

However, meaningful redress of these issues is effectively prevented by the same power dynamics that facilitated the growth of the geosciences described here. Indeed, the structure of Western academia, including the geosciences, is built upon imbalances of power (Clauset et al. Reference Clauset, Arbesman and Larremore2015; Moss Reference Moss2018; Marín-Spiotta et al. Reference Marín-Spiotta, Barnes, Berhe, Hastings, Mattheis, Schneider and Williams2020). These kinds of power imbalances are ubiquitous, yet seldom addressed, in professional or academic settings (Marín-Spiotta et al. Reference Marín-Spiotta, Barnes, Berhe, Hastings, Mattheis, Schneider and Williams2020). Here, we illustrate how perception of the history of paleontology reflects these imbalances of power, before discussing how these dynamics reinforce racist structures and norms within academia.

Note that any meritocracy will involve some imbalance of power, and that’s why people like this are also trying to water down merit-based advancement in science. My emphases in the below.

Students are often taught that science is apolitical, unbiased, and egalitarian, when in reality it is not. Because of this, reality is often supplanted by a racist, colonialist, and inherently misleading narrative (Sabbagh Reference Sabbagh2017). Most Western paleontology and geoscience courses are taught by white faculty who control course curricula (Dutt Reference Dutt2020; Marín-Spiotta et al. Reference Marín-Spiotta, Barnes, Berhe, Hastings, Mattheis, Schneider and Williams2020). Without uncomfortable examination of current teaching methods and textbooks, most paleontology courses will continue to emphasize the contributions of white (often male) Western scientists to paleontology, while simultaneously failing to address the racist beliefs of Western scientists, the knowledge of BIPOC scholars, and the historical and modern exploitation of BIPOC communities to benefit Western institutions. This amounts to white supremacy (Truss Reference Truss2019; Table 1). Failure to recognize and address unequal power dynamics and their effects on academia only serves to entrench these behaviors.

Imagine a minority student (or any student) signing up for a paleobiology course only to learn not the facts and theories of paleobiology, but a litany of how the field has been used to suppress the marginalized—and is still being used that way! What minority student would want to enter such a field? And wouldn’t students who want to learn paleobiology be a bit peeved that they are repeatedly indicted for white supremacy?

I love biology and I have studied a bit of paleobiology, too (I pride myself in having read nearly everything that Steve Gould wrote, including his final behemoth tome, which you don’t need to read). But I’m not sure I would have loved evolutionary biology so much if, at the outset of my studies, I was told that I was entering a field riddled, like a house with termites, with bigotry, racism, and white supremacy. Darwin, Fisher, Galton, Wallace, and even poor Mendel—racists all. Let’s leave science classes for science (with perhaps a rare mention of perfidy), and move this kind of stuff to the area of “studies” and history of science.

In the end, articles like the one above will serve to chill the speech of dissenters, for who dares criticize this article? The fear is that you’ll be called a racist, sexist, or other species of bigot. Some of us, though, aren’t put off by those epithets, nor do we have anything to lose professionally.

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Monarrez, P., Zimmt, J., Clement, A., Gearty, W., Jacisin, J., Jenkins, K., . . . Thompson, C. (2021). Our past creates our present: A brief overview of racism and colonialism in Western paleontology. Paleobiology, 1-13. doi:10.1017/pab.2021.28

Some science listening from the BBC

July 30, 2021 • 10:00 am

Reader Dom called my attention to today’s BBC Science in Action program, which contains several items of interest. You can hear the 35-minute show by clicking on the site below and clicking “listen now”:

There are four bits:

Start – 12:20. A discussion with Elizabeth Turner about her new evidence for 890-million-year-old animals (spongelike creatures), which I wrote about yesterday.

12:20-18:55. A discussion with Cambridge University’s Dr Sanna Cottaar about the “Insight” probe on Mars’s surface and scientists’ attempt to deduce the structure of the planet.

18:55-26:45: Prof Lesley Lyons from the University of Missouri discusses the similarity of the genome of cats to that of humans, and how that could be used for medical purposes in humans. I’m not keen on this because it implies that they’re going to experiment on cats. As she says, “they’re bigger than mice and cheaper than primates”.

26:45-end: A remembrance of Steven Weinberg, who died a week ago. There are extracts from two BBC interviews with Weinberg as well as discussions of his work by fellow scientists.

Oldest evidence for animals found? New sponge-like fossil is 890 million years old, several hundred million years older than next oldest animal

July 29, 2021 • 9:15 am

First, we have to know what biologists mean by “animals”. In brief, they are multicellular organisms comprising eukaryotic cells (“true cells” with a nucleus and nuclear membrane, as well as organelles like mitochondria). Or, to be more specific, I’ll give the Wikipedia definition:

Animals (also called Metazoa) are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage in which their body consists of a hollow sphere of cells, the blastula, during embryonic development.

Long before animals existed, living organisms existed, but these were cyanobacteria (“blue green algae”) and other microbes, not regarded as animals. The first cyanobacteria date back about 3.5 billion years, only a billion years after the Earth formed. The cyanobacteria are identified in fossil stromatolites—layered reef-like structures formed by the accretion of bacteria. Stromatolites are still forming in some places on Earth, like Shark Bay, Australia.

But when did the first metazoan, or “animal” appear? For that you can use either fossil or molecular evidence.

The earliest fossil scientists regard as an animal is Dickinsonia from the Ediacara fauna, dated about 540 million years ago. Scientists think it’s an animal because its lipid biomarkers, which you can extract from fossils and the sediments above and below them, include cholesteroids, compounds found exclusively in animals. Dickinsonia is known only from imprints, like the one below, and its affinities are a mystery.

Molecular data, from which you can construct a phylogenetic tree of living animal groups and then extrapolate backwards, have shown that animals probably originated between 650 and 850 million years ago, but we have no animal fossils from that period. Those trees also show that perhaps the earliest animal was similar to sponges, for sponges seem to be the most “basal” animals—those that branched off the animal tree before other groups. This makes sponges the “sister group” of all other animals.

Now a new paper in Nature by Elizabeth C. Turner of Laurentian University in Canada has pushed the oldest animal fossil back a long way: several hundred million years—to 890 million years ago! And, in fact, the fossil shows features of early sponges, verifying the molecular conclusions.

Now not all paleobiologists agree that what Turner found is an animal—some say the structures observed may have a microbial origin—but Turner herself is pretty confident, as are some other paleontologists. So let’s take this conclusion as “likely, but not certain”. Surely further work will either strengthen or weaken Turner’s evidence.

You can access Turner’s paper by clicking on the screenshot below, or downloading the pdf here. The reference is at the bottom of this post.

Investigating the Little Dal Reef Formation in Northwestern Canada, itself a kind of stromatolite, Turner collected rocks between 1992 and 2018, and, in thin sections of those rocks, observed “vermiform” (worm-shaped) microstructures filled with calcite “spar”, or calcium carbonate crystals. These tube-like structures join and divide in a branching network, just like the tubules of modern sponges, some of which have a calcite skeleton. (The tubules of modern sponges allow them to circulate water through their bodies, getting food and oxygen.) These wormlike structures are surrounded in the fossils by a calcite “groundmass”, which may be the external body of the sponge.

Here’s what Turner says about these interconnecting tubules and why she regards them as early sponges:

The shape, size, branching style and polygonal meshworks of the Little Dal vermiform tubules closely resemble both spongin fibre networks of modern keratosan sponges (Fig. 2a–c) and vermiform microstructure either demonstrated or interpreted to be sponge-derived in diverse Phanerozoic microbial, reefal and non-reefal carbonate rocks. The compositional and textural homogeneity of the microspar groundmass supports an origin through permineralization of a pre-existing biological substance, rather than incremental accumulation of detrital sediment or microbial carbonate that passively incorporated complexly anastomosing tubular microfossils. Variable preservation and association with geopetal peloid accumulations are familiar aspects of Phanerozoic sponge taphonomy In previous work, detailed comparison of the three-dimensional characteristics of vermiform microstructure with branching cylindrical organism types yielded no convincing alternative to the sponge interpretation

Here are subfigures (a)-(b) of her Figure 2 showing the fossil network compared to that of a modern sponge (c), with the captions below (click photo to enlarge).

(From Fig. 2 of the paper): a, Well-preserved vermiform microstructure exhibits a polygonal meshwork of anastomosing, slightly curved, approximately 30-μm-diameter tubules embedded in calcite microspar (KEC25). Scale bar, 500 μm. b, Enlarged rectangle from a, showing branching tubules forming three-dimensional polygons intersected at various angles by the thin section; clear calcite crystals, about 10–20 μm in width, fill tubules in groundmass of more finely crystalline calcite (dark grey). Scale bar, 50 μm. c, Three-dimensional fragment of spongin skeleton from a modern keratosan sponge, illustrating its branching and anastomosing network of fibres (incident light). Scale bars, 100 μm (main panel), 20 μm (inset).

There are other pictures as well, but the first two are the heart of the matter. You may not think they look like much, but they do show the interconnecting, ramifying tubules with the light-colored calcite crystals typical of some groups of sponges. The area where these putative fossils are found is 890 million years old. And these fossils are older than the next oldest and indisputable sponge fossils by 350 million years!

Turner hypothesizes that these early organisms couldn’t compete with the reef-building cyanobacteria, but were able to find “oxygen oases” to use the oxygen produced by the cyanobacteria. The association of these putative sponges with oxygen-producing bacteria may be one piece of evidence that these are indeed metazoans, which of course require oxygen.

As I said, some paleobiologists disagree about whether these are animals. You can hear a ten-minute Nature-sponsored discussion with Turner, some supporters, and some doubters here. I highly recommend that you listen to this short but lucid discussion.

One other point: these organisms must have survived at least one of the periods of extensive glaciation and freezing known as “Snowball Earth“, when the entire planet was either completely frozen or almost covered with ice except for some open water. (The most extensive was between 700 and 600 million years ago.) In the linked article, author Laura Poppick says this about that period:

What did life on Earth look like at the time, and how did it change as a consequence of these events?

There were certainly bacteria and there were also algae and unicellular primitive animals, or protists.

There is also evidence that the first multicellular animals originated at this time, probably something like sponges.

Well, according to Turner, the first multicellular animals, probably something like sponges, originated nearly 200 million years earlier than this.

Stay tuned to see how the dispute about the nature of these fossils progresses. Are they animals or simply remnants of bacterial activity? As Turner says in the interview, “We are quite confident” that these are spongelike animals. “It’s almost,” she adds, “a no-brainer.”

And here’s Turner in the field:

(From source): Elizabeth C. Turner, geology professor at Laurentian University, conducting geological fieldwork on northern Baffin Island in 2012. (Supplied photo/Laurentian University)

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Turner, E.C. 2021. Possible poriferan body fossils in early Neoproterozoic microbial reefs. Nature (2021). https://doi.org/10.1038/s41586-021-03773-z

Faith versus fact: the problem of Native American creationism and paleoanthropology in North America

June 14, 2021 • 9:30 am

This article in Quillette caught my eye because it was about science—paleoanthropology—and its conflict with faith. The authors are a pair of anthropologists who have written a book about the topic, which is the perennial conflict between scientists on the one hand and Native Americans claiming ancient human remains that, they say, are their ancestors.

Click on the screenshot to read:

The title refers to a meeting of the SAA in April when Weiss gave a talk about the obstructionism of Native American creation myths as they affect paleoanthropology in North America. Although the talk is certainly germane, and provides food for thought (see below), it was in effect “erased” by the SAA, who refused to post it despite their pledge to do so. It was the only talk that wasn’t posted. The reason is clear: going up against the claims of Native Americans, even if those claims can’t be supported, is a no-win situation. As Weiss writes:

The new SAA president, Deborah Nichols, subsequently contacted me to let me know that the video of our live talk would not be posted by the SAA for others to view, due to reports of hurt feelings. (We had previously relied on the SAA’s emailed assurance to presenters that “sessions will be available for viewing on demand within 24–36 hours after their original broadcast, until July 17, 2021.”) Furthermore, we learned, the SAA would not even provide us with the video. (And so we re-recorded the talk, which you can find here.) Another SAA statement was then put out to inform readers that “the SAA board finds the presentation does not align with SAA’s values,” and mentioned that “the board categorically rejects the Weiss-Springer position.”

Here’s the 13-minute talk that Weiss re-recorded after the SAA refused to post it:

There was substantial other pushback on both professional and social media. Here’s an example of a reaction by an “indigenous archeologist” to Weiss’s abstract of the talk: archaeologist.”

Why was this abstract accepted @SAAorg? This is completely unacceptable and anti-Indigenous. This is why people are leaving your organization. Stop giving this type of work a platform. pic.twitter.com/L2zSXMjPyt

— Emily Van Alst (@emilyvanawesome) April 15, 2021

Hurt feelings again!

Well, we all know about these conflicts, and it’s conceivable that for some of them the Native Americans have a right to the bones and artifacts found by archaeologists, who of course lose the chance to study them. But in most cases that “right” is dubious, for the genetic connection between those claiming the bones and the person whose bones are claimed is tenuous at best. Often it rests solely on creation myths: many Native Americans claim that despite scientific evidence that the Americas were populated by “modern” H. sapiens who crossed the Bering Strait from Asia about 15,000 years ago, their ancestors have lived in America forever. Further, to establish that the bones belong to a specific tribe is almost impossible, because bones from people of multiple “tribes” have been found in one locality, and there was considerable migration within North and South America.

Genetic analysis could conceivably settle the question, but without the bones you don’t have the DNA, and even so it’s hard to narrow down ancient DNA to a specific existing group of Native Americans, who are fairly closely related to each other. It’s even worse because the U.S. government passed laws saying that establishing ancestral (i.e., genetic) affinity isn’t necessary: “cultural evidence”, like oral traditions and creation myths, is sufficient. That immediately puts science at loggerheads with superstitions, superstitions that can be demonstrably incorrect.

As an example, Weiss and Springer discuss the famous Kennewick Man, 8,400- year-old remains of a man found in 1996 in Kennewick, Washington. It’s one of the most complete ancient North American skeletons ever found (see photos at bottom), and dates pretty close to the time when Asians began populating the Americas. But the remains were claimed by several tribes of Native Americans, although, according to the authors “the oldest known American tribe, the Hopi, reliably dates its history to only about 2,000 years ago.”

This started a decade-long court case between Native Americans, scientists, and the U.S. Army Corps of Engineers. The case wasn’t resolved until 2004, and in favor of the scientists, though the remains have since been returned to a “coalition of Pacific Basin tribes” for reburial.

In the meantime, scientific studies of the skeleton, including use of DNA, showed that it was actually more closely related to “modern American Indian populations of Central and South America who are not ‘Native American'” by the U.S. government’s regulations. Using ancestry rather than creation myths, those other populations would have a stronger claim to the bones than would North American tribes.

In the meantime, scientists were able to find out a great deal of information from the skeleton. As the article states,

The greatly delayed scientific study was finally carried out, and the result was a magnificent peer-reviewed 2014 volume, edited by Jantz and Douglas Owsley of the Smithsonian Institution, titled: Kennewick Man: The Scientific Investigation of an Ancient American Skeleton. The studies revealed Kennewick Man’s age, sex, bone morphology, and bone chemistry, as well as modifications to the skeleton incurred during his life. This information, in turn, allowed inferences as to his food intake, food production, and other physical activities, and diseases and injuries he’d endured.

His affinities with other prehistoric and modern populations and individuals were also revealed by these studies. Kennewick Man’s dietary reconstruction from nitrogen isotopes (elements found in a variety of food sources that settle in bones and teeth, and which can be used to reconstruct eating and weaning patterns) revealed a diet composed mainly of marine foods. This differed from the previous view of Paleoindians as big game hunters. Kennewick Man also had bony growths in his ear canals called external auditory exostoses, which some have argued may have impacted his hearing and were related to chronic ear infections.

Kennewick Man had multiple injuries—including a projectile point (a spear head) in his pelvic bone. Chatters argued that this injury never healed properly and likely caused lifelong pain. Anthropologist Della Cook, on the other hand, suggested that the lack of reactive bone (which is evidence of bone healing from injury or infection) in the CT-scans suggests that Kennewick Man’s injury healed quickly. Interestingly, these two perspectives were both published in this 2014 book—an example of the open-minded manner in which science should be conducted and evaluated.

All of this information would have been lost had the repatriationists been successful. No other Paleoindian is as well studied as Kennewick Man, and many were reburied with just a simple osteological report. Such reports may include only the remains’ antiquity, sex, estimated age, and other basic information; and often are written up by undertrained students and marginal scholars who are not subject to peer review, and who do not report their findings in a way that contemporaries can validate. . .

Weiss and Springer describe other cases in which cultural tradition blocked scientific study, as well as scientific study that did succeed in finding out stuff about early Native Americans.

So what should the rule be? Of course, as a scientist who values scientific fact over creation myths or oral tradition, I’m biased in favor of empirical study. But if remains can be traced to a specific tribe or group of tribes, showing the bones to be more closely related to that group than to other tribes, one might consider tribal claims to be valid. Even so, perhaps there should be an allowed period of scientific study, say two years, before the remains are returned to present-day tribes for reburial or various rites. After all, it’s not as if these bones belong to a present family of Native Americans, like the remains of someone’s son recovered and returned after a battle.

But I don’t think that claims based only on “oral tradition” or “creation myths,” should be honored at all. In such a case, the remains should then be available to scientists. After all, if we honor such superstitious claims, we are also tacitly honoring the creation myths of anybody, including Christians, Scientologists, and Muslims, each of which has its own creation story. That is government entanglement with religion.

And it’s a double entanglement: one with the myths of Native American groups, and the other with the religion of Wokeism, which makes the SAA into an organization that renders decisions based not on empirical considerations, but on ideology and identity politics.

Here’s the skeleton and skull of Kennewick Man:

New report: Bacteria can remain alive for over 100 million years!

July 30, 2020 • 10:00 am

Well cut off my legs and call me Shorty (is that ableist?). A new report in the journal Nature Communications shows that some bacteria can remain dormant for over 100 million years in marine sediments—an unbelievable amount of time for an organism to remain “alive”—if you call it “alive.” I do: after all, the bacteria collected and revived by the researchers retained their ability to metabolize, take up labeled organic substances, and reproduce. Dormancy, to me, at least, is not the same thing as “death”.

Click the screenshot to read the paper (the pdf is he re and the full reference is at the bottom).

The experiment was laborious yet the results are simple. If you want to know the gory details, the paper is there for your reading.

In short, the authors sampled clay sediments of different ages from the South Pacific Gyre, and did so in a way that, they aver, precluded contamination with modern bacteria. Supporting their claim that the bacteria they found in the inside of sea-floor cores were really bacteria in situ, they argue that the clays are almost impermeable to bacteria, with very low pore size, and there are thick impermeable layer above the sampled sediments. And there were strict precautions to prevent contamination.

To see if any bacteria in the sediments were capable of biological activity including reproduction, they tested for “anabolism” (the synthesis of molecules) by incubating the bacteria with oxygen (controls lacked oxygen) as well as radioactively labeled molecules that could be taken up and made into proteins and other molecules. The added molecules included ¹³C₆-glucose, ¹³C₂-acetate, ¹³C₃-pyruvate, ¹³C-bicarbonate, ¹³C-¹⁵N-amino acids mix [mixture of 20 Amino Acids], and ¹⁵N-ammonium. Another control involved killing any bacteria with formaldehyde. The researchers could then visualize the bacteria and see, through fluorescence microscopy and radioactive visualization, if the precursor molecules had been taken up by bacteria.

Finally, the researchers could isolate bacteria at various times (the samples for activity, growth, and bacterial presence were taken at 3 weeks, 6 weeks, and 18 months) to see if the bacterial titer was increasing, i.e., they were dividing. Finally the authors isolated RNA (16S rRNA) from individual bacteria, amplified it, sequenced slow-evolving RNA, and saw what groups of living bacteria the ancient bacteria belonged to. (This assumes that we can still recognize the groups from modern sequences, but these molecules evolve very slowly).

The upshot:

1.) The aerobic bacteria (bacteria that require oxygen) were still viable, initiating metabolism and reproduction even in sediments as old as 101.5 million years. Anaerobic bacteria, which don’t require oxygen, didn’t do nearly as well, and the authors suggest that even low oxygen concentrations in the sediments over geological time simply kills anaerobic bacteria.

Here’s a figure from the paper showing photos of the bacteria, with the same bacteria then examined for uptake of added molecules. The caption is complicated, but you can see that, especially with added amino acids (and oxygen), the cells glow furiously (d and h are electron-microscope images of the same bacteria shown fluorescing in the rows).

(from paper): Cells from incubations of U1365 9H-3 with 13C-bicarbonate and 15N ammonium (a–d) and 13C,15N-Amino acid mix (e–h). (a, e) SYBR Green I-stained cells under fluorescence microscopy. b, c, f, g Ratio images of 13C/12C (b, f) and 12C15N/12C14N ratios (c, g) of the same regions imaged in a, e, demonstrating locations of 13C and 15N incorporation. Color-scale ranges of the ratios are shown as numbers appearing at top and bottom of the color bar. The background membrane region, which is identified by fluorescence images, is excluded from the ratio calculation and shown as black background. d, h. Secondary electron (NanoSIMS) images of the same regions in a, e. Bars represent 5 µm. Similar images were processed for obtaining the dataset (Supplementary Data 1) of substrate incorporations for 6986 individual cells.

2.) The bacteria divided, as measured by the increase in numbers over time in the samples.

3.) Anaerobic bacteria were much harder to find metabolizing than aerobic bacteria. The former were effectively defunct.

4.) The lineages of bacteria identified as persisting in the sediments, judged from sequencing them and comparing the 16S rRNA to modern samples, include Actinobacteria, Bacteroidetes, Firmicutes, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Deltaproteobacteria, and cyanobacteria (“blue-green algae”). It would be interesting to compare the sequences of these early species with their modern relatives to see exactly how much and what kind of evolution has gone on.

5.) How did they survive? One thought was that they formed dormant spores, which can last a long time in bacteria. But this suggestion is ruled out because none of the bacteria identified were from spore-forming lineages. It seems the bacteria simply became dormant, surviving without any—or hardly any—detectable metabolism, and without reproduction.

This raises the question: were these things really alive for 101.5 million years? I can’t see why not, unless you think that something that becomes dormant is dead, and then, Lazarus-like, revives when the dormancy is broken. If you take the authors’ word that sufficient precautions were taken to prevent contamination with modern bacteria, then what we have here are the oldest living organisms on Earth.

h/t: Jeremy

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Morono, Y., Ito, M., Hoshino, T. et al. Aerobic microbial life persists in oxic marine sediment as old as 101.5 million years. Nat Commun 11, 3626 (2020). https://doi.org/10.1038/s41467-020-17330-1

A tiny 10-cm dinosaur that ate bugs

July 29, 2020 • 9:00 am

Note: The classification of “dinosaur” above isn’t totally accurate, for the creature discussed below is an archosaur, a member of the group that gave rise to dinosaurs, pterosaurs, and crocodilians. But we might as well call it a dinosaur, as few people know what an “archosaur” is.

The ancestors of the dinosaurs could not have been big, for they evolved from amphibians, and amphibians, for a number of reasons, are limited in size. But this new paper in PNAS shows that some of the earliest ancestors of dinos were very small—not just small, but tiny. The new species described below, which falls into a group that later diverged into pterosaurs (flying reptiles) and the dinosaurs, was only 10 cm tall, the distance between my index fingers in the photo below:

Click on screenshot to read the paper; the pdf is here, and reference at bottom of post.

The partial skeleton of this tiny creature, whose dentition suggests it ate insects, was discovered in 1998 in Southwestern Madagascar. Although the age of the specimen is a bit uncertain, a good estimate is about 237 million years.

Here are some drawings of the parts of the skeleton they recovered, including leg bones, a forearm bone, and the jaws (interpreted as coming from single individual), and a figure showing where they fit into the body (figure F). The size, estimated from the bones, which clearly put the species in the ancestral group Ornithodira (also known as Avemetatarsalia), show that the creature was only about 10 cm tall. It must have been really cute: a pet-sized reptile. Note that the length of the scale bar on the left, showing the femurs, is one centimeter (about 4/10 of an inch), while on the right the scale bar for the jaws is only about 40 mm (1.6 inches):

(from paper): Anatomy of the femur and maxilla of Kongonaphon kely gen. et sp. nov. (UA 10618). (A) Right femur in anterolateral, (B) posteromedial, and (C) proximal views. (D) Right maxilla in right lateral and (E) palatal views. (F) Preserved elements in the holotype, UA 10618, presented in a silhouette of Kongonaphon. aof, antorbital fenestra; at, anterior trochanter; fht, tip of femoral head; fp mx, facial process of maxilla; ft, fourth trochanter; mx f, maxillary foramen; pf, palatine fossa; pmt, posterior medial tubercle; t, maxillary tooth. Illustrations credit: American Museum of Natural History/Frank Ippolito.

The authors named the fossil Kongonaphon kely, meaning “tiny bug slayer”. They explain the etymology:

. . . derived from kongona (Malagasy, “bug”) and φον (variant of ancient Greek φονεύς, “slayer”), referring to the probable diet of this animal; kely (Malagasy, “small”), referring to the diminutive size of this specimen.

The teeth, as you can see in the drawing above, were simple ones: conical and without serrations. That suggests that the creature lived on insects (I used “bug” in the title as a generic word for insects, though technically, bugs are in the order Hemiptera). The estimated size of 10 cm comes from the size of the preserved femur, which is only about 1.6 inches long. The specimen wasn’t a juvenile, as the authors saw signs of arrested growth in the fossil bones. The bones also indicate strongly that K. kely was bipedal, like T. rex and the theropods.

To place this individual in the phylogeny of dinosaurs and their ancestors, the authors did a computer analysis of 422 characters derived from these bones, and K. kely fell out in group B of the phylogeny below, which includes the dinosaurs and the pterosaurs (the relative size of this tiny species is shown to the right). I’ve put a box around K. kely.

B is the base of the Ornithodira, the group that gave rise to all dinosaurs and pterosaurs, and you see that K. kely is an early (“basal”) member of this group

(from paper): Body size of early avemetatarsalian (bird line) archosaurs mapped onto a consensus supertree, based on the current phylogenetic analysis (SI Appendix) and recent analyses (22). Silhouettes are scaled to estimated femoral lengths for the labeled nodes (SI Appendix, Table S1): A, base of Avemetatarsalia (represented by Teleocrater); B, base of Ornithodira (represented by Ixalerpeton); C, base of Dracohors (Silesauridae + Dinosauria) (represented by Silesaurus); and D, base of Saurischia (represented by Herrerasaurus). Silhouettes credit: Phylopic/Scott Hartman/Mathew Wedel, which is licensed under CC BY 3.0. Silhouette of Kongonaphon to the right of the taxon label is to scale.

Here’s a reconstruction of K. kely, eyeing a beetle, from Science Alert; (artist’s impression by Alex Boersma):

Now the diminutive size of this creature doesn’t mean that the common ancestor of all dinos and peterosaurs was this small. But it does imply that the ancestor of those groups, which falls out in a “reconstruct-the-size” analysis, was smaller than we thought. K. kely itself could have been the result of a “miniaturization event” in which a somewhat larger ancestor produced some tiny descendants. The estimated size of ancestral Ornithodiran is estimated fo be about 13.3 cm, or about 5.3 inches tall, and the ancestral species of the Dinosauromorphs, which includes dinos and birds but not pterosaurs, is even smaller, about 6.5 cm (2.5 inches)!

What are the implications of this beyond showing that the ancestral dino and ancestral dino/pterosaur were likely a lot smaller than we thought? Well, first of all, we have no idea why these early creatures were so small. My own guess is that since insects had already evolved, there was an “open niche” to specialize in eating them, and if you want to make a living as a terrestrial reptile eating insects, you can’t be the size of a T. rex.

The authors note that the small size of this species (and probably its close relatives) accounts for the absence of ornithodirans in Early and Middle Triassic faunas, for small creatures have tiny, fragile bones that aren’t easily preserved. In fact, our best knowledge of early Ornithodirans previously came from sediments in Argentina whose nature allowed for the preservation of small animals.

Finally, the authors speculate that these small species would have a problem with heat retention, since they were ectothermic (“cold blooded”). Small creatures have a higher surface area/volume ratio than larger ones, which means more heat lost by radiation. Thus, suggest the authors, the filaments covering the bodies of some dinos and pterosaurs—which might have been homologous to feathers that eventually covered the theropods—would have been useful as insulation. This sounds good, but of course there are plenty of extant small insect-eating reptiles, like geckos and anoles, that make a fine living without feathers. But it would still be useful to look at these early, small species to see if there is any evidence for filamentous body cover.

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Kammerer, C. F., S. J. Nesbitt, J. J. Flynn, L. Ranivoharimanana, and A. R. Wyss. 2020. A tiny ornithodiran archosaur from the Triassic of Madagascar and the role of miniaturization in dinosaur and pterosaur ancestry. Proceedings of the National Academy of Sciences 117:17932-17936.

Did humans occupy the New World over 30,000 years ago? New paper suggests it.

July 23, 2020 • 9:45 am

This new paper in Nature (click on screenshot, pdf here, reference at bottom) has the potential to be the big human-paleobiology story of the last several years. It reports finding human occupancy of a high-altitude cave in Mexico during the last glacial maximum (LGM): about 26,000 years ago. And that, say the authors, implies that humans have been in the New World since more than 30,000 years ago—more than doubling the time we thought they’d been here. Previously, the best guess was that humans crossed the Bering Strait from Siberia about 15,000 years ago, and then spread through the Americas.

Click on the screenshot below to get the paper (free through the legal app Unpaywall, or you can make a judicious inquiry).

Before we accept these results as overturning the received wisdom about humans in the New World, though, there has been some criticism of the paper, as you can see in a precis in Science by Andrew Curry.

The cave where the finds were made sits atoop a remote mountain in the Mexican state of Zacatecas, about 2,740 m high, and has been studied since 2012. Although dry and barren now, it was thought to be verdant during the LGM, with water, plants, and plenty of edible animals nearby. Researchers worked there for a month at a time, camping in the cave and hauling water and food by donkey from the nearest town.

What made the researchers suppose that the cave was occupied by humans were several things, most prominently 2000 specimens of what looked like sculpted tools. Here’s a figure showing some of these putatively manufactured objects:

(from paper): a, Core. b–e, Flakes; inlay in b emphasizes an isolated platform. f–j, Blades. k–o, Points. Scale bar, 3 cm. Most items are from component SC-B; d and m belong to SC-C. One Pseudotsuga sp. (Douglas fir) charcoal fragment closely associated with the bifacial preform shown in m in stratum 1223 was dated to 27,929 ± 82 uncalibrated radiocarbon years BP (PRI-5414). More lithic finds are shown in Extended Data Figs. 5, 6.

Now I would have thought that by now paleoanthropologists would be able to distinguish non-human rock artifacts from real, chipped tools, but apparently that’s not the case. As one critic says in the Science writeup:

Critics point out that the tools are simple and don’t resemble other toolkits from the Americas, raising the possibility they’re the product of natural breakage. “They look like they could be artifacts, but why aren’t they found anywhere else in the landscape?” wonders David Meltzer, an archaeologist at Southern Methodist University. The tools’ consistency is also remarkable, he says. “If these tools are real, why are they only found—so far at least—in this one spot over a 10,000-year period? Humans adapt and adopt new technology.”

The tool-making conclusion, at least, must remain tentative. There was also burned wood that was radiocarbon dated, implying human campfires, but the critics again say that this could derive be from “wind-blown” wildfires. The researchers also used OSL dating of quartz from the sediments, which tells you when the mineral was last exposed to light, ergo when it was laid down.

Finally, the researchers trawled the cave for DNA, which they could sequence to see what kind of animals and plants were there. The fauna included bats, mice and other rodents, marmots, goats, and sheep, as well as birds, though this could have come from more recent occupancy. Plant DNA included forest species like spruce, pines, grasses, and palms. The disappearance of cold-adapted species and forest trees that gave way later to Joshua trees and grasses suggests that the sediments in the cave did go through the late Glacial Maximum, which was followed by a period of dryness.

Notably, no human or humanoid DNA was found in the cave, which would have gotten people much more excited about this find.

THE UPSHOT

How strong is the evidence for human presence in the Americas beginning 30,000 years ago? The 30,000 years is a guess by the authors, derived from guessing how long it would take humans to get to a 26,000-year-old cave residence in Mexico after crossing from Siberia. In terms of the age of the cave itself, that seems reasonable, but the evidence for human occupation is largely the “tools”, and their provenance is doubtful. And if humans inhabited the cave continuously for millennia, as the authors suppose, then why wasn’t human DNA found there? My judgment, and I’m a tyro here, is that the evidence is intriguing but not terribly strong. A lot hinges on whether the “tool-like” stone artifacts really were chipped by hominin hands.

On the other hand, the Science article says that there is a cave in the Yukon that’s yielded dates as old as the Mexican cave (about 24,000 years), but although it contains thousands of animal bones, there are “few stone tools or cut marks.” But other researchers are beginning to think that people came to America earlier than we thought, and could have spread quickly by traveling along the West coast by boat, avoiding the largely frozen interior. Here’s a tweet (h/t: Matthew) showing sites where there could have been earlier habitations:

News & Views: Two studies in Nature report evidence that the initial human settlement of the Americas happened earlier than is widely accepted. Some of the evidence suggests settlement began at least 10,000 years earlier than was generally suspected. https://t.co/OBuIQzBI7v

— Nature (@nature) July 23, 2020

How good are the dating methods? From what I read, they seem fairly reasonable, and they used at least two methods that give about the same dates. The question is not how old the cave is, but whether humans lived there and made the tools and charcoal.

What happened to the people? Part of the reason we think humans have been in the New World for only 15,000 years is not just evidence from habitation, but from DNA of Native Americans (note: there are some older estimates). If that’s the case, why doesn’t the DNA give a consistent age of 30,000 years from when Native Americans branches off from East Asians? One possibility is that the early arrivers went extinct without leaving descendants, so we wouldn’t find a genetic signature of their existence. Given that some paleoanthropologists see evidence of an early arrival from other sites, like that in the Yukon, the possibility of extinction seems unlikely.

All in all, this is an exciting finding, and may well be right, but we’ll have to let the experts fight it out.

Excavating in the cave, a photo from the Science precis: