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 stromatoliteslayered 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.

Dickinsonia

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)

_______________

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

Readers’ wildlife photos

May 7, 2021 • 9:06 am

By Greg Mayer

The following photos were sent to me by a colleague, and were taken during a trip to Costa Rica during December, 2011- January, 2012. We’ll start with the crocodiles of Rio Grande de Tarcoles, which are an attraction for both Costa Rican and foreign tourists, who gather at the highway bridge to see the many large crocodiles gathered there. I was told on one of my visits there that there used to be some sort of slaughterhouse or rendering plant, and that the offal was dumped in the river, which initially attracted the crocodiles. People now feed them, although I think this is officially discouraged.

American Crocodile, Crocodylus acutus, Rio Grande de Tarcoles, Costa Rica, January 2012.
American Crocodile, Crocodylus acutus, Rio Grande de Tarcoles, Costa Rica, January 2012.
American Crocodile, Crocodylus acutus, Rio Grande de Tarcoles, Costa Rica, January 2012.

She also saw crocodiles on a trip to Tortuguero.

American Crocodile, Crocodylus acutus, on boat trip to Tortuguero, Costa Rica, January 2012.

Also at Tortuguero was this heron, a widespread species which is also found in the southeastern US, breeding at least as far north as New York.

Yellow-crowned Night Heron, Nyctanassa violacea, Tortuguero, Costa Rica, January 2012.

A visit to the area of Fortuna revealed a couple of species of mammals. This is a normally colored Mantled Howler Monkey,

Non-blonde Mantled Howler Monkey, Alouatta palliata, N of Fortuna, Costa Rica, January 2012.

while this one is “blonde”; I’ve never seen a howler of this color myself.

Blonde Mantled Howler Monkey, Alouatta palliata, N of Fortuna, Costa Rica, January 2012.

There were also bats.

Proboscis Bats, Rhynchonycteris naso, N of Fortuna, Costa Rica, January 2012.

And last but not least, because they are practically honorary cats, a squirrel from Volcan Poas.

Variegated Squirrel, Sciurus variegatoides, Volcan Poas, Costa Rica, December, 2011.

How different languages depict dog and cat sounds

March 1, 2021 • 2:30 pm

I was asking my French-Canadian friend Anne-Marie (the travel guide) if the French use “vau vau” as the spelling for the dog barking that Americans write as “bow wow”, and she said no, that the French spelling is “wouf wouf”. Well, that’s close enough, but then I thought that someone should compile a list of all the different languages’ spelling of what we spell as “bow wow” (alternatively, “woof, woof”) or, for cats, “meow”.  Foolish me—I should have known that there are tons of such lists on the Internet. Anne-Marie called my attention to two of them.

Take this one from BarkPost: which gives sixteen national versions of “bow wow”. I’ll show just three that struck me:

Meong-meong? Seriously? But in the video below, which gives not the written but the verbal renditions, you can hear native speakers from 70 countries give their national versions of dog and cat noises. It IS “meong meong”!  What you can conclude is that, in general, most people hear dog noises the same way, but there are some odd variants. But there is much less international variation of cat sounds (why?). Note, though, that Thailand is very odd!

One-off: a melanistic emperor penguin! (+ leucistic lagniappe)

November 23, 2020 • 1:30 pm

Well, I’ll be! IFL Science highlighted the presence in Antarctica of the only melanistic penguin I’ve ever heard of. We’ve all seen or heard of melanistic squirrels and jaguars or leopards (both called “black panthers”); it’s a genetic trait and can be either dominant (one gene copy and you’re black) or recessive (two copies required). But penguins?

For a panoply of melanistic species, go here, and click on the screenshot to read the article:

The one-minute BBC video is below, and though I worried this penguin may be subject to predation or lack of potential mates, the IFL Science article (and the video) says it’s doing fine:

Adult emperors have black heads and wings, gray backs, and white bellies, with their distinctive yellow-orange markings around the neck. This particular penguin spotted when the Dynasties team were filming the Emperor episode in Antarctica, is almost entirely black, but does have the odd patch of white on its chest and wing tips, and a splash of yellow around its neck.

Sometimes, sadly, it’s not good to stand out in a crowd, though. The mutation can make animals with melanism more easy to spot by predators. In this penguin’s case, not just because it may be more visible on the ice, but because penguins’ white bellies make them look invisible to predators swimming below by helping them blend in with the light from the surface.

Though, as the BBC points out, this one isn’t doing too badly, having survived into adulthood.

In fact, according to the BBC the penguin is doing just fine. Filmed amongst hundreds of its besuited brethren and looking healthy, it appeared to show signs of looking for a mate while huddling for warmth with the other penguins.

It looks lonely to me, but maybe I’m just anthropomorphizing.

UPDATE: Reader Bill Turner sent this photo, taken by his wife Yvette, and added the caption,

“Your post today on a melanistic Emperor penguin prompted me to send the attached photos of a leucistic gentoo, taken at the Chilean Captain Arturo Prat Base on Greenwich Island on 24 December 2018. The bird was, apparently, quite a familiar sight around the island.”

I hope this white bird found a mate, too.

h/t: Nicole

Asiatic lioness adopts leopard cub

February 28, 2020 • 9:00 am

by Greg Mayer

A paper just published by Dheeraj Mittal and colleagues in Ecosphere reports an Asiatic lioness (Panthera leo persica) that adopted a leopard (Panthera pardus) cub, nursing and feeding it along with its own two cubs for six weeks.

Asiatic lioness, leopard cub, and lion cub in the Gir Forest, India. Photo by D. Mittal.

As WEIT readers know, Asiatic lions survive in only a single relict population in Gujarat in northwestern India, where they coexist with leopards (but not tigers, which have been extirpated in Gujarat). As the only lions in all of Asia, they are carefully monitored by Indian wildlife biologists, and in December 2018 they spotted the leopard cub in the company of the lions. From the paper:

Contrary to the accepted understanding of lion–leopard interactions, in December 2018, we came across an adult free-ranging Asiatic lioness (Panthera leo persica) taking care of a leopard cub (P. pardus fusca) in addition to her own young cubs in the Gir forests of Gujarat, Western India (Fig. 1A). Over the course of the next one and a half months,we intimately monitored this lioness that was recorded to nurse the leopard cub and rear it as her own (Fig. 2). The leopard cub (a male of~2 months with characteristic blue haze in its eyes that indicated its very young age; Fig. 1B) was always found to be associated with the lioness: suckling from her, feeding from kills that she made, and playing with its foster siblings (Fig. 2). The prolonged duration and the ecological context of the observed foster care between these two sympatric and competing felids are bizarre and stimulate intriguing behavioral questions.

The New York Times interviewed one of Mittal’s co-authors, Stotra Chakrabarti of the University of Minnesota.

“The lioness took care of him like one of her own,” nursing him and sharing meat that she hunted, Dr. Chakrabarti said.

His new siblings, too, were welcoming, playing with their spotty new pal and occasionally following him up trees. In one photo, the leopard pounces on the head of one of his adoptive brothers, who is almost twice his size and clearly a good sport. “It looked like two big cubs and one tiny runt of the litter,” Dr. Chakrabarti said.

He has been studying the park’s lions for nearly seven years. This unlikely association “was surely the most ‘wow’ moment I’ve come across,” Dr. Chakrabarti said. His fellow researchers with an Asiatic lion conservation project in India, some who have been watching the big cats for decades, had “also not seen anything like this,” he said.

Sadly, the leopard cub was found dead after about six weeks. An autopsy revealed that it died of a congenital femoral hernia; it had not been abandoned or killed by the lions, and, given its condition, it was probably doomed from the start.

From an evolutionary perspective, rearing an allospecific cub would not be advantageous. Indeed, leopards and lions are competitors, and will kill one another as opportunity arises.  But, to paraphrase Yoda, the Baby Schema is strong with this one, and the juvenile features of essentially all amniotes that elicit the “awwww” response in humans seems to work in lions, too. It leads in this instance to what Mittal el al. call a nonadaptive ‘reproductive error’.


Mittal, D, S. Chakrabarti, S.B. Khambda, and J.K. Bump. 2020. Spots and manes: the curious case of foster care between two competing felids. Ecosphere 11(2):e03047. pdf

Readers’ wildlife photos: Stunning animal architecture

January 28, 2020 • 8:00 am

Nicky Bay is a superb photographer of small animals. I don’t think he’s technically a “reader” of this site, but I wanted to put his pictures under this category. Nicky has a Flickr site here, a Twitter page here, and a website, Macro Photography in Singapore, here. I’ve featured his photography three times on this website (here, here, and here).

He recently had a wonderful post called “5 Mysterious Structures From The World’s Smallest Architects,” but I’ll give the link below the fold. First I want you to guess what kind of creature made these structures. Nicky let me use the photos, which are copyrighted and cannot be reproduced without permission.

1.)  A log cabin made of twigs:

2.) A “jungle tent” made of leaves:

3.) Cage fortress!

4.)  Poop barricade!

5.) Web tower. 

Click on “read more” to see the answers:

Continue reading “Readers’ wildlife photos: Stunning animal architecture”

Darwin and the Falklands

December 1, 2019 • 8:30 am

[JAC: Greg wrote about Darwin, oceanic islands, and the Falkland Islands fox about six years ago, and gives the link to that post below. But I thought I’d add the link here at the top as well, because it’s a very informative summary of how islands buttressed Darwin’s theory of evolution, as well a discussion about how a fox could have colonized the distant Falkland Islands.]

by Greg Mayer

Jerry’s back from his southern sojourn now, and may have made some posts from Chicago by the time you see this, but as he settles back in I thought it would be good to recall the lessons that another famous evolutionary biologist learned in the Falklands. Although we all associate Darwin with the Galapagos, his visit to the Falklands (also during the Beagle voyage) supplied an important bit of evidence in his thinking about islands, and the phenomena of island life were crucially important components in his argument for evolution.

Darwin was a bit perplexed by the Falklands. In many ways they seemed like oceanic islands—islands never connected to a continent, which had received their biota from across the seas by what Darwin called “occasional means of transport”. There was only a single native species of land mammal on the Falklands: the Falkland Islands fox, which was clearly related to South American foxes. (South America has a modest radiation of canids, which are variously called dogs, foxes, or wolves in English). The mammal fauna was thus depauperate (few species); disharmonious (lacking major ecological or taxonomic groups); and showed affinity to the fauna of the nearest continent (the effect of distance)—all of these are characteristics of oceanic islands.

Canis antarcticus, by George Waterhouse, from the Zoology of the Beagle. The increasing human population, and consequent increased disturbance and hunting, led to the extinction of the Falklands fox by the late 1800s.

How the fox got to the Falklands is an issue that concerned Darwin, but that’s not what I think was most important. (The issue of how they arrived, and when, was largely solved a few years ago, and we discussed it here at WEIT: the short answer is that lowered sea levels during the last glacial maximum greatly shortened the distance to the continent, and the fox came across, perhaps floating on ice floes, as Arctic foxes do.) The problems that the Falklands helped Darwin with most was why oceanic faunas were depauperate and disharmonious. Darwin’s evolutionary hypothesis was that it was difficulties of dispersal that led to oceanic faunas being apparently “undercreated”.

But there was an obvious alternative explanation: the ecological conditions on the islands are unsuitable for a species-rich, harmonious, fauna, despite seemingly appropriate physical environmental conditions. The oceanic faunas were not “undercreated”, but inhabited by the ecologically appropriate species.

These competing explanations are easily tested by introducing exotic species to the island, and seeing how they fare. If they become established, then the cause of their absence is a failure of dispersal, not a failure of environmental suitability. This is where the Falklands helped Darwin, I think. The Galapagos in the 1830s were still nearly pristine, but the Falklands showed him the fauna of an island with little direct habitat disturbance, and a small human population. But the people who had settled the Falklands brought their animals with them. At the time of his visit, Darwin recorded wild populations of cattle, horses, pigs, rabbits, rats, and mice, with cats, dogs and sheep coming later. The Falklands were thus quite capable of supporting a diverse and harmonious mammalian fauna; the mammals just needed help getting there!

So we can see that exotic mammals of all sorts do quite well in the Falklands, and that Darwin’s evolutionary hypothesis is thus supported. Although I’ve read up on the Falklands, Jerry’s visit there is the first by anyone I know, and he has provided firsthand reports on, and pictures of, the exotic mammals. So here again is a bovine, the Belted Galloway:

and a dog:Jerry tells me that sheep are “all over the place there!”, but, unfortunately, he didn’t get any pix of them. So here’s one that I found on the Internet, by Jeremy Richards, who has also sagely captioned it:

The Falklands’ dominant species, together © Jeremy Richards

What were the first animals?

October 31, 2018 • 11:45 am

by Matthew Cobb

I’ve just finished making a BBC World Service radio programme about the first animals. Anyone, anywhere in the world, can listen to it (it’s only 28 minutes long!) – you just have to register with the BBC (free, rapid and cost- and spam-free). Click on the pic to go to the BBC website:

The programme deals with two different ways that researchers are studying this question – by looking at fossils, and at DNA. In both cases I interview researchers and – in the case of the Ediacara – get to handle some fossils. I also ate some 600 million year embryos at Bristol University (to see what they tasted like, obviously), but we didn’t include that in the programme. . .

The fossil data relate to what are called the Ediacaran biota – strange fossils from before the Cambrian, around 570 million years ago. The fossils are very hard to interpret – they don’t look like much alive today – but an amazing technique for analysing cholesterol molecules in the rock, so organic molecules preserved for all that time, has confirmed that Dickinsonia, the thing in the picture above, was an animal. Other techniques involve looking at large numbers of Ediacaran fossils and seeing how their distribution relates to those of modern animals. All the data suggest that some of the Ediacaran weirdos were indeed animals, although we cannot know if they are the ancestors of any animal alive today.

The DNA data focuses on a different question, which DNA can answer – which of the groups of animals alive today was the first to branch off the tree of life? Traditionally there has been a straightforward answer to this: sponges, which are nerveless and tissueless. But 10 years ago comparative genomic studies dropped a bombshell – they suggested that the first group to branch off were the ctenophores or comb jellies. This has caused a huge row because it would mean either that nerves evolved twice – once in the ctenophores, and once in our ancestors, after the nerveless sponges branched off – or that the huge sponge group somehow lost the genes for producing nerves.

Many biologists (myself included) don’t like either of these options, and prefer the sponges as the first model, but the data are persistent. Or are they? I spoke to experts on both sides of this argument, which has caused quite a hoo-haa in the zoological community for the past decade.

Anyway, go ahead and have a listen – download it and listen to it on public transport or while you are exercising. NB: I made the programme with ace producer Andrew Luck-Baker.

If you are a teacher, especially if you teach animal evolution, please get your students to listen to it.

Friday duck report and wildlife humor

September 28, 2018 • 2:30 pm

Duck update: Honey was gone this morning, though she was here with James all day yesterday. At 7:30 a.m., James was again swimming disconsolately around the pond, and even attempting to quack, though not much of a noise came out. (Previously he’d just uttered low quack-y noises, but now he opened his bill wide and tried a real quack, with pretty dire results.) I’m convinced he was mourning Honey’s absence.

Then, at 10:30, Honey was back! Lord knows where she went; this is a real emotional roller coaster, but surely presages the Big Migration. At any rate, here’s James sitting on the “bathtub” this morning waiting for his mate. He’s standing on one leg and stretching a wing. I like this picture a lot. James is a good mate and I don’t think Honey can do better:

Let’s end the week with some humorous wildlife photos, in particular the finalists from the 2008 Comedy Wildlife Photography Awards. You can see all the photos here, but I’ll put up my favorite five six. Coincidentally, three of them involve bears.

© Jonathan Irish/The Comedy Wildlife Photography Awards 2018
© Geert Weggenhe/ Comedy Wildlife Photography Awards 2018
© Amy Kennedy/The Comedy Wildlife Photography Awards 2018
© Roie Galitz/The Comedy Wildlife Photography Awards 2018
© Valtteri Mulkahainen/The Comedy Wildlife Photography Awards 2018

Lagniappe: