Why Evolution is True is a blog written by Jerry Coyne, centered on evolution and biology but also dealing with diverse topics like politics, culture, and cats.
This post is entirely based on a fantastic set of fossils posted over at Updates from the Paleontology Lab which is run by the Virgina Museum of Natural History (VMNH) and updated by Dr. Alton “Butch” Dooley. My thanks to him for the pics!
If you’re like me, you are going to need some help with this one. Belostomatids (no, me neither) are water bugs – true bugs, the kind that won’t get entomologists irritated if you refer to them as ‘bugs’, cos they are. Here’s a pic of a giant water-bug, taken by Alex Wild, and found on the Tree of Life website:
These things can get pretty big and pretty bitey and are sometimes known as ‘toe-biters’ (the clue’s in the name). They’re in the same infra-order as back-swimmers, and the adult forms can fly. Even cooler, they are one of the exceptions in which males play an important role in parental care, keeping the eggs on their back until they hatch. Here’s a video of the process:
Anyway, the VMNH has been looking at triassic fossils collected at Solite Quarry, and regularly posting about them. There are all sorts of dinosaurs and plants to be found there, but they also find belostomatids… So, spot the belostomatids in this fossil (the white line is a fossilised plant stem):
There are *15*!
Ok, now you’ve got your eye in, how many in THIS one?
The answer is at least four (the different sizes are probably different nymphs):
Finally, to give you an idea of how lovely these fossils can be, here’s a beautifully-preserved belostomatid, sadly missing its head, but you can see its wings and one of its swimming legs:
To close, here’s an amazing video of one of the giant water bug toe-biters nomming a garter snake. Quite impressive (the cameraperson gets the focus sorted out after 30 secs or so):
Just out in eLife, an Open Access journal that aims to rival Science and Nature, is this fantastic fossil of an aquatic fly larva from the Chinese mid-Jurassic (around 165 MY ago), published by Chen et al. Soft-bodied animals rarely fossilise well, but the Chinese fossil-hunters have been able to find three of these fossils, exquisitely preserved. The beast is called Qiyia jurassica – Chen et al write: ‘Qiyia is from the Chinese ‘qiyi’ meaning bizarre; jurassica is a reference to the Jurassic age of the fossils.’
Here’s the ‘holotype’ (ie the one they made their taxonomic descriptions on the basis of, and in this case the best of the three fossils) (click to see the full size photo). This is Figure 1 from the paper and the scale bar in A is 5mm.
Panel D shows the amazing preservation of an odd structure, which they interpret as ‘a thoracic sucker with six radial ridges, unique in insects’. Here’s a hi-res picture of the six ridges (again, click to see it in all its glory). Will you look at this? It looks like it has been preserved in alcohol!
The authors think these ridges – which they suspect are modified prolegs (fly maggots don’t actually have legs) were covered in a thin layer of skin forming a sucker that would have enabled the maggot to hang onto a prey’s smooth flesh, so that its bitey mouthparts (D and E in the figure above) would then be able to suck the blood of their prey.
On the basis of a detailed anatomical description, the authors conclude:
This combination of primitive and derived features demonstrates that Q. jurassica is a stem lineage representative of the Athericidae (water snipe flies), a family sister to the more familiar horse flies (Tabanidae).
The spiracles on the sides of the maggots indicate that these were air-breathing (this is typical of dipteran maggots – even larvae that spend their whole life in the water, such as rat-tailed maggots or mosquito larvae, breathe air rather than dissolved oxygen in water, which requires gills). They also have two structures at the rear, which may have been used for water-breathing, or for dealing with salt. So, it had a sucky thing and bitey mouthparts and it lived in water. The authors state:
Suckers are widespread in aquatic ectoparasites such as leeches, fish lice, and lampreys (Kearn, 2004) which require more suction power to avoid becoming dislodged; other aquatic ectoparasites without attachment organs embed themselves in skin or muscle, such as cyclopoid copepods (anchor worms) (Kearn, 2004). In addition to the sucker, the stiff, upward directed bristles and apical hooks on the prolegs (Figure 1F) are also specialized attachment structures. These morphological adaptations provide compelling evidence that Q. jurassica adhered to a host as an ectoparasite, providing further specialization for a dense, watery habitat.
And what were they eating? Well the fossil beds at Daohugou are full of fossil salamanders, so the authors suggest that they were sucking the blood of Jurassic salamanders. Here’s a reconstruction of the beast. The head end is at the left, with the sucker on the ventral surface of the thorax. The mouthparts are at the far left:
And here’s an imaginary view of what it might have looked like, attached to an oddly-cheery-looking salamander:
One of the things that is interesting about the fossil, apart from its stunning detail, is that it pushes the origins of blood-sucking further back. In an accompanying piece (also open access, hooray), EnriquePeñalver and RicardoPérez-de la Fuente point out that ectoparasitic blood-sucking (i.e. sitting on the outside and sucking), evolved several times over in the insects, as shown in this figure (our maggot is bottom left, with the star shape, meaning its precise affinities aren’t known):
As to what the adult fly might have looked like, here are two modern representatives of the Athericidae and the Tabanidae, respectively:
This stupendous set of fossils shows that there are amazing things to be discovered in the earth, and in particular in China. We are living through an amazing period in palaeontology!
This was just put up: an audio discussion between Seth “The Thinking Atheist” Andrews and Don Prothero, a prolific paleobiologist and author of one of my favorite evolution books, Evolution: What the Fossils Say and Why it Matters. The introduction begins at about 6:30, and the show continues for about an hour and five minutes after that.
Prothero talks not only about fossils, but about cryptozoology, punctuated equilibrium and, of course, his continuing battles with creationists. It’s a very nice program, and Don is quite eloquent. You could do worse than listening for an hour.
The Q&A from listeners begins at 42:40.
By the way, you can find the video of the debate between Matt Dillahunty and Sye Ten Bruggencate here.
Here’s an appropriate post for Darwin Day: a new discovery of some very old fossils.
You remember the Burgess Shale fauna, right? The whole story, although it’s since been revised, is given in Steve Gould’s excellent book Wonderful Life (1989). Discovered by Charles Wolcott in the Canadian Rockies in 1909, the site’s shale-preserved fossils were largely neglected until students Simon Conway Morris and Derek Briggs analyzed them decades later. They’re from the Cambrian, a bit more than 500 million years ago.
The first analysis suggested that they belonged to many groups (perhaps phyla) no longer living, suggesting that there had been a luxuriant explosion of life that was subsequently pruned away by extinction. The assemblage also contained a fossil chordate, Pikaia gracilens, perhaps a relative of our ancestors, although it wasn’t a vertebrate:
Pikaia gracilens, about 1.5 inches (3.8 cm) long. It may have been closely related to the ancestor of all chordates, or even vertebrates.
The diversity of weird, un-placeable fossils led to the message of Gould’s book: had the “tape of life” been rewound, and had extinction not removed most of the Burgess Shale fauna, life today might have descended from those creatures and would be very different from what we see on Earth today. Gould’s message was one of contingency: evolution is unpredictable because of the vagaries of the environment. (Of course, while I see evolution as unpredictable by humans, I see it largely as deterministic, since environmental perturbations must themselves obey the laws of physics. Evolution is only non-deterministic insofar as mutations might be the result of completely indeterministic processes involving quantum-level events.)
At any rate, a closer examination of the fauna by Briggs and Conway Morris showed that most of the anomalous beasts were actually members of extant groups, like arthropods, annelids, and sponges, so the fauna really wasn’t as much of an outlier as Gould suggested. That somewhat overturned his idea that the types of life on Earth today were purely the result of contingencies.
Nevertheless, there are still animals in the original Burgess fauna that defy identification; one of them is the bizarre Opabinia regalis, which looks like a shrimp with a vacuum-cleaner hose attached to its head. Here’s a specimen from the nice Smithsonian site on the Burgess shale (first link in this post):
Opabinia. As the Smithsonian site notes, “Wielding a long flexible proboscis tipped with grasping spines, its reconstructed image was greeted with laughter as a pretty good joke when first presented at a scientific meeting in 1972.”
Another weird one was the six-foot predator Anomalocaris canadensis (the genus name means “abnormal shrimp”) a large predator that may be closely related to ancient arthropods. Here’s a reconstruction and a fossil of its two forelimbs:
Later comparable fauna, also remarkably well preserved, were found in the Chengjiang biota of Yunnan, China, a series of Cambrian shale fossils about 525 million years old. They’re notable for containing what may be the first known jawless fish (“agnath,” a group that comprised the ancestral vertebrates), Myllokunmingia. Here’s a fossil of that species and then a reconstruction (it’s somewhat speculative; we don’t know whether it had eyes). Myllokunmingia was about 1.1 inches (2.8 cm) long:
Which brings me to the point of this post: a new paper in Nature Communicationsby Jean-Bernard Caron et al. It describes a site 50 km from the Burgess Shale site (and not too far from where I’m speaking in Kamloops this spring), that, like the original Walcott site, contains a remarkable array of wonderfully-preserved invertebrate (and one chordate) species, 22% of which are new to science. It also contains many fossils known from the Chengjiana fauna, showing that some species had a broad distribution.
The specimens haven’t yet been worked up and many aren’t yet identified as to group, but some are known as identical species from other places. When the new ones are identified, however, we may see some severe revision of the early history of life.
The paper is not much more than a description of the site (called “Marble Canyon”) and a brief description of the fauna, with some pictures, so I’ll show both. A nice article in the Globe and Mail (be sure to watch the one-minute video showing the beautiful location) gives some of these photos; my captions are lifted that article:
The fossil bed was discovered in 2012, in a section of Kootenay National Park in British Columbia that cannot be accessed by trails. Although the team is not sharing the site’s precise location – to protect it from pillaging by would-be fossil hunters – Dr. Caron said it was near a scenic feature called Marble Canyon.
“It’s on the side of a mountain like any other mountain,” said Alex Kolesch, a manager with Parks Canada. “To be able to discern what’s there, you would really need to know what you’re looking for.”
The team first stumbled upon the site while looking for exposed sections of rock similar to that found in the Burgess Shale. One evening, they came to a place where it seemed that fossils were littering the ground. Upon closer inspection, they realized it was no fluke, but the eroding edge of a significant deposit that previous expeditions had missed. Within days, there were pulling out high-quality specimens of ancient marine life in stunning numbers.
First the site and some excavations:
A view of the quarry site and Diego Balseiro.Paleontologists have discovered a vast and ancient fossil bed in Kootenay National Park which they say could equal or surpass the famous Burgess Shale deposit just 42 kilometres away. The new find is half a billion years old, similar in age to its famous counterpart,but it contains many new and previously undocumented life forms. (Jean-Bernard Caron)
The animals. If you think you know your groups, guess which phyla these belong to. The paper, which unfortunately is not free, gives some answers. For example, the third photo below shows a new species of arthropod:
Naraoia, another of the specimens discovered at the Kootenay site. All the specimens found at the site lived on the ocean bottom and were later covered with a muddy silt, which gradually became a fine-grained rock.Molaria, another of the specimens discovered at the Kootenay site. Dr. Caron’s teams also found fossil types that had previously only been seen in Asia, along with others never encountered by scientists anywhere.New arthropod ROM 62976, discovered at the Marble New Burgess Shale Fossil Site in Kootenay National Park Canyon site. (Jean-Bernard Caron/ROM)Polychaete, one of the specimens discovered at the Kootenay site. The fossils are remarkable for the degree of preserved detail.Leanchoilid, one of the specimens unearthed at the Kootenay site. The new find dates back to the Cambrian Period, some 505 million years ago. (Jean-Bernard Caron/ROM)
Here are two pictures from the Nature Communications paper. The first shows another chordate, Metaspriggina, which has remarkable preservation of the internal organs, including the heart and liver, and, especially, the eyes (“ey” in figure), so we know that eyes had already evolved by this time. The scale bar is 5 mm long (0.2 inches):
And here is something I didn’t know about, a “bivalved arthropod,” apparently with some kind of bivalve-like shell. This one is new to science and not yet named; the scale line is 10 mm (0.4 inches), so you can see that these specimens are small:
The fossils include the first preserved neural tissue from any specimen of this period, but its meaning awaits further analysis.
Happy Darwin Day: one of your ancestors might be in the pictures above!
Charles R. Marshall, once my colleague here at Chicago, is now a professor at the Department of Intergrative Biology at the University of California at Berkeley. Along with a handful of other people, including Andy Knoll, Jim Valentine, and Martin Brasier, Marshall is one of the most respected experts on the evolution of early life. He specializes in the Cambrian Explosion and has written several influential papers on it, including the 2006 paper given at bottom (free download).
Marshall has just published a review of Stephen Meyer’s ID book, Darwin’s Doubt, in one of the world’s most prestigious scientific journals, Science (reference below, but I’m not sure readers get a free download). And his review is a complete pan, though written without rancor or “shrillness.”
The name of Marshall’s review, “When prior belief trumps scholarship,” gives away the game, for Meyer’s book is completely motivated by his attempt to show that an intelligent designer was responsible for the Cambrian Explosion of animal phyla around 545 million years ago. Meyer’s book has been trashed by every competent scientific reviewer I’ve seen, including Don Prothero and Nick Matzke, but this is the first major review in a major scientific journal.
Meyer won’t take much comfort from words like these, which accuse him (as have other reviewers) of “a systematic failure of scholarship”. But of course that’s what’s required when you have to push aside any truth that might impede the return of Jesus:
Meyer’s scientific approach is negative. He argues that paleontologists are unable to explain the Cambrian explosion, thus opening the door to the possibility of a designer’s intervention. This, despite his protest to the contrary, is a (sophisticated) “god of the gaps” approach, an approach that is problematic in part because future developments often provide solutions to once apparently difficult problems.
Darwin’s Doubt begins with a very readable review of our knowledge of the Cambrian explosion. Despite its readability and a plethora of scholarly references, however, there are substantial omissions and misrepresentations. For example, Meyer completely omits mention of the Early Cambrian small shelly fossils and misunderstands the nuances of molecular phylogenetics, both of which cause him to exaggerate the apparent suddenness of the Cambrian explosion.
. . . And so even after reading the flawed first part of his book, I dared hope that Meyer might point the way to fundamental problems in the way we paleontologists think about the Cambrian explosion.
However, my hope soon dissipated into disappointment. His case against current scientific explanations of the relatively rapid appearance of the animal phyla rests on the claim that the origin of new animal body plans requires vast amounts of novel genetic information coupled with the unsubstantiated assertion that this new genetic information must include many new protein folds. In fact, our present understanding of morphogenesis indicates that new phyla were not made by new genes but largely emerged through the rewiring of the gene regulatory networks (GRNs) of already existing genes (1). Now Meyer does touch on this: He notes that manipulation of such networks is typically lethal, thus dismissing their role in explaining the Cambrian explosion. But today’s GRNs have been overlain with half a billion years of evolutionary innovation (which accounts for their resistance to modification), whereas GRNs at the time of the emergence of the phyla were not so encumbered. The reason for Meyer’s idiosyncratic fixation with new protein folds is that one of his Discovery Institute colleagues has claimed that those are mathematically impossibly hard to evolve on the timescale of the Cambrian explosion.
As Meyer points out, he is not a biologist; so perhaps he could be excused for basing his scientific arguments on an outdated understanding of morphogenesis. But my disappointment runs deeper than that. It stems from Meyer’s systematic failure of scholarship. For instance, while I was flattered to find him quote one of my own review papers (2)—although the quote is actually a chimera drawn from two very different parts of my review—he fails to even mention the review’s (and many other papers’) central point: that new genes did not drive the Cambrian explosion. His scholarship, where it matters most, is highly selective.
The ending is very polite (Charles isn’t a contentious guy), but still sticks a knife in the book:
Meyer’s book ends with a heart-warming story of his normally fearless son losing his orientation on the impressive scree slopes that cradle the Burgess Shale, the iconic symbol of the Cambrian explosion, and his need to look back to his father for security. I was puzzled: why the parable in a book ostensibly about philosophy and science? Then I realized that the book’s subtext is to provide solace to those who feel their faith undermined by secular society and by science in particular. If the reviews on Amazon.com are any indication, it is achieving that goal. But when it comes to explaining the Cambrian explosion, Darwin’s Doubt is compromised by Meyer’s lack of scientific knowledge, his “god of the gaps” approach, and selective scholarship that appears driven by his deep belief in an explicit role of an intelligent designer in the history of life.
This review is important as previous critical reviews have been dismissed by the Discovery Institute (DI) because their authors weren’t recognized experts on the Cambrian Explosion (this is, for example, what the DI did to Don Prothero’s cogent but negative review that was published on Scepticblog. Well, Marshall’s review can’t be dismissed so easily: it’s in a refereed journal—a major journal—and is by a recognized expert on the topic of Meyer’s book.
One thing is absolutely predictable: the DI will simply dismiss this review, although I don’t know on what grounds. Given that they have none, they’ll probably just whine that the Scientific Establishment can’t handle the truth (shades of Jack Nicholson!). Despite its claim to be science, Intelligent Design never has, and can’t, accept scientific criticism. So they go their own merry way, peddling their lies and religion to the subset of Americans who want real scientific assurance that God and Jesus are in there somewhere.
It does say something, though, that modern creationists can’t just dismiss science, but have to tackle it on its own turf. And they always fail when they try.
I’m spending most of the day writing now, and it’s difficult to find time to read scientific papers and report on them. So do excuse me for a while if I summarize new findings from (reliable) journalistic results, even though I’ll scan and link to the original paper when possible.
There are two evolution-related findings of note this week. I’ll highlight one today and one tomorrow.
First, Homo floresiensis, the three-foot “hobbit” human whose remains were discovered on the Indonesian island of Flores in 2003, has now been designated as a real species truly distinct from H. sapiens. This species lived fairly recently—38,000-12,000 years ago, when modern humans were already colonizing the New World—but is very distinct from H. sapiens. Because of its size and the resemblance of the skull to those seen in certain human diseases (hypothyroidism, microcephaly, etc.), some scientists speculated that this was not a tiny archaic species living at the same time as modern humans, but simply a single pathological individual of H. sapiens.
A new analysis by Baab et al. (link and free download below) suggest however, that this really was a tiny hominin species. Extensive morphological analysis of the single existing skull from Flores, along with modern H. sapiens, both “normal” and suffering from a variety of syndromes suggested to have produced the Flores skull, as well as a variety of early hominin species, shows that the Flores skull is more similar to that of H. erectus than to nearly all pathological specimens, and is thus likely to truly represent a new species. (See the New York Times report by John Noble Wilford.)
Here’s a cast of the “LB1” skull from Flores (the only existing one) that was used in the authors’ analysis:
Note that this hominin came up only to your hips (check out the reconstruction at Washington’s Museum of Natural History), and had a brain about 400 cubic centimeters: one third that of modern humans and the size of one of our earliest hominin relatives, Australopithecus afarensis. Here’s how the hobbit compares to a modern human:
Stony Brook University anthropologist William Jungers with an artist’s rendition of Homo floresiensis.
Here’s the figure from the Times:
Researchers found that the cranium of Homo floresiensis, known as hobbits, top, was more similar to skulls of various human predecessors than to modern Homo sapiens, bottom.
The authors of the paper conclude with the following paragraph, allowing one possible pathology as an explanation:
Our analyses corroborate the previously suggested link between LB1 and fossil Homo and support the attribution of this specimen to a distinct taxon, H. floresiensis. Furthermore, the neurocranial shape of H. floresiensis closely resembles that of H. erectus s.l. and particularly specimens of early Eurasian H. erectus, although it is unclear whether this latter affinity is best attributed to a close phylogenetic relationship or to a size-related convergence in shape. These results also counter the hypotheses of pathological conditions as the underlying cause of the LB1 neurocranial phenotype, with the possible exception of posterior deformational plagiocephaly, a condition without significant adverse health effects/
