Creationists are much vested in the idea of “suddenly” — they love the idea of inserting the fingersnap of God into every abrupt transition. This is why they are infatuated with the Big Bang and the Cambrian Explosion, and why they flirted with the idea of renaming “Intelligent Design” to “Sudden Origins” theory. If something had no antecedents, no gradual build up, well then, we have to explain it with “God did it!”.
Unfortunately, the media plays along with it. I found a bit of scientific misinformation on the Raw Story — such obvious stupidity that anyone with any basic training in evolutionary biology would have caught it. I just gave my first year biology students an exam, and they would have caught it (I hope). Multicellular life did not arise in the Cambrian — it’s much older than that.
Here’s the story. A fossil of a multicellular organism was found, and…here comes the hype.
For those involved in and interested in the history of life and its evolution- including the inception of multicellular eukaryotes(organism with cells) – Virginia Tech released some very exciting news recently.
According to research conducted by Shuhai Xiao, a Virginia tech professor of geobiology, in conjunction with partners from the Chinese Academy of Sciences, there is new evidence that indicates complex multicellularity (plant and animal life) actually appeared about 60 million years before previous information had indicated. The study found three unusual fossils that show that multicellular organisms may have appeared 600 million years ago and not in the Cambrian Explosion as was previously thought.
No one with any knowledge of the field thought that multicellular organisms arose in the Cambrian. NO ONE. Multicellularity has evolved multiple times — I’ve seen estimates of 50 independent origins — and there are some fossils of multicellular alga that are over 3 billion years old.
Six hundred million year old fossils are not new. The Doushantuo formation contains phosphatized fossil embryos that are 600 million years old.
The molecular evidence also points to a much older origin. The last common ancestor of arthropods and chordates, for instance, was a multicellular animal that I learned way back in the 80’s probably lived about 700 million years ago; I’ve seen other molecular analyses that propose dates over a billion years ago instead. The point is that in the last 40 or so years of my career, everyone has known that multicellularity is old, old, old, and that it precedes the Ediacaran.
The only reason that we see stories otherwise is a lot of ignorance and confusion injected into the popular press by the uninformed and the ideologically twisted creationists. So this might be a very nice and interesting fossil — we should always welcome new data from the Ediacaran period — but it ain’t surprising at all, and it should fit in well with all of our other evidence. The large animal forms of the Cambrian had antecedents that evolved over hundreds of millions of years, and no one is at all impressed by another tiny piece of evidence that confirms that well-established fact.
Oh, and Raw Story needs a scientist to vet their science reports.
They should get a scientist to vet both their science reports and their gossip reports. That’s got to work out better than having a gossip journalist vetting everything.
I’m sorry, I meant that it’d be better than a gossip-specialist EDITOR vetting everything, as is apparently the modern procedure now.
There were not only multicellar but large and complex organisms before the Cambrian.
Anyone with an interest or Google knows about the Ediacarian fossils.
McMenamin is not a trustworthy source — he’s pro-ID, an endorser of Stuart Pivar’s balloon animal evolution nonsense, and discoverer of a Triassic Kraken.
I think it is the second episode that covers Ediacaran (named for the discoveries in Australia) fossils: http://www.pbs.org/wgbh/nova/earth/australia-first-years.html
The whole series is great though – the down under is so cool. I wish someone would do the same kind of thing with the US as canvas.
This makes me miss the intellectual rigour of the Halletstonian Sea Zorias.
You’d think it wouldn’t be too much trouble to just call up the relevant department of a university and asking someone. In my experience, university professors are happy to explain anything you’d care to know. The trouble isn’t getting them to talk, it’s getting them to shut up.
That’s obviously bogus. Everyone knows Krakens belong to the Paleogene.
Wow -Even my non-scientific brain caught that. If I’m remembering correctly, the Cambrian explosion was named that because there was a huge proliferation of new species at that time. It would just make sense that there were multi-cellular creatures long before that.
There are way too many people today who either slept through basic biology classes or who were never exposed to actual science classes in the first place.
I saw that story and noticed the same mistake.
Aren’t there billion+ year old ichnites interpreted as bunches of some species of jelly washed up on a beach?
Can’t remember where I saw that, but porifera’s LCA is older than 600mya, IIRC. And I remember the Doushantou embryos as well.
Hell, I’ve been interested in the evolution of life long enough that I’m familiar with the Ediacaran synonym “Vendian”. (In fact, I caught myself using it by accident yesterday.)
And I have no training in bio at all, just a persistent interest – not nearly as obsessive as those of creationist douchgabbers – and a willingness to read and learn.
Okay, looking around, I can’t find any evidence of jelly-related ichnites older than mid-Ediacaran, and those are disputed.
I don’t know why I remember seeing an article like that, but y’all should know my memory was faulty on that point.
Sponges, however, are the most likely candidate for a biochemical signature appearing in rocks as old as 713mya, and are clearly present in well-preserved Doushantou fossils that have been shown to be 580mya. So, yes, LCA of Porifera is almost certainly > 600mya.
Raw Story isn’t the only source to blame here.
1. The article at Raw Story was “Posted with permission from redOrbit.com”
2. The source that they link to is a Virginia Tech site. I’m assuming its one of those PR pieces along the lines of “look at what our people publish”, wherein it begins:
So its crappy editors all the way down.
Raw Story, RedOrbit.com, and Virginia Tech News.
We can’t blame it on just creationists. They are getting plenty of help.
Hallettestoneion. Yes, seriously. Google even suggests it!
And yes, his name was Hallett, without an extra e at the end or anything.
Too bad the original video seems to be gone. Playlist.
Hmm, AFAIK, the oldest fossil other than stromatolites is Grypania spiralis, which is thought to be an algae.
They are only one billion, five hundred sixty eight million years off. source
My lecture notes on the topic: http://www.geol.umd.edu/~tholtz/G204/lectures/204ediacaran.html
If Otavia is a legit sponge, that pushes Porifera back into the Cryogenian. Of course then you have to deal with Porifera, the wastebasket taxon to end (begin?) all wastebasket taxa, but they’re at least metazoans.
Like Snidely W @ #11, I followed the footprints to the VT press release. The Raw Story article quotes the press release, not the scientist or the Nature article. The VT story does quote the author who has a slightly different tone. The article has a link to the Nature article for those of you with the knowledge and access to read the actual piece.
But they did cite Katie Spicer from International Business Times. I’m sure IBT is a reliable source for science journalism. Right?
(*snicker*) So how old are 600 million year old fossils?
“Suddenly” to a physicist might be a tiny fraction of a second while to a geologist or biologist “suddenly” could be tens of millions of years.
@ #1: As the museum guide, employed for 24 years explained, the fossils he was showing visitors were 600,000,024 years old.
That was to #18. Sorry, but I think you get it anyway.
@16 octopod:
Are sponges definitely so bad? I know some people have treated them as several groups, some closer to us than others.
But I have also seen some people suggesting that they are actually closer relatives to us than Ctenophora, either interpreted as those developing complex tissues independently, or sponges being secondarily simplified. Which seems to go with treating them as a single group.
I have no idea which position has more evidence, would be interested if you know more.
Jiminy. I knew complex life was around before that, and that’s from reading the How And Why Wonder Books back in the 60s!
Octopod: in fairness of the discussion, these web notes were written for the Spring semester, and subsequently the following paper has come out: http://onlinelibrary.wiley.com/doi/10.1111/brv.12090/abstract
Compare and contrast:
The Virginia Tech press release:
The Raw Story “story”:
So, the VT press release got it right — no hyperbole at all. The “reporter” for Raw Story messed it up completely.
There is a curiosity about multicellularity that I haven’t seen much discussion of.
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Animal-like multicellularity has evolved only once. All the other instances of multicellularity are either plantlike/algalike or funguslike or slime-mold-like. In addition to all the eukaryotic examples of all three, prokaryotes also have examples of them: cyanobacteria, actinobacteria, and myxobacteria.
About 6000 years, according to some. God put them there to test us.
Trebuchet
Did we pass?
Do we know that? While arthropods & chordates are clearly related through certain signaling pathways, what about protostomes? What about pre-bilaterian radiations?
I’m not saying that it only evolved once. I’m just saying that I don’t know and would like to see more evidence.
Moreover, imagine that heterotrophism + mobility + multicellularity evolved more than once, but one lineage had a 20mya head start. Isn’t it possible that one lineage would literally gobble the other up?
For that matter, what evidence do we have that fungi have never had a capacity for mobility? Those capacities were pretty rudimentary for a long time. If one lineage of heterotrophs couldn’t compete in finding and/or hunting food actively, loss of mobility isn’t an impossible evolutionary outcome. If the fungi lineage never got more advanced than porifera, it might be possible for them to return to sessility.
Anyway, I’m not asserting that heterotrophism + mobility + multicellularity evolved more than once, I’m just curious about why you seem so certain.
All animals do have various adaptations to multicellularity in common; the quickest example I could find is that all except sponges have gap junctions.
Also, arthropods are protostomes.
They’d compete before that’d even happen.
Chytrids, the sister-group to all other fungi, have a single-celled reproductive stage with a “flagellum” (undulipodium, cilium). All others lack even that. No contractile fungal cells are known either; there’s nothing analogous to a muscle.
@ David Marjanović 29
Your post makes me wonder about some items that have been on my mind.
The evolutionary source and utility of gap junctions reminds me of what the source of muscle tissue might have been. One possibility influencing the evolution I’ve been wondering about is the use of calcium signalling in the system.
On interesting geological feature that might matter is cap carbonates. If calcium is involved in the contractile response, is there a connection between environmental calcium and primitive movement? Are cap carbonates biogenic? Brains basically control movement in a more complex way and calcium signalling in an evolutionary context is interesting.
Cnidarians have those epithelial-muscle cells, and the collencytes of sponges are contractile.
I have no idea if environmental calcium ever gets into a range where it could influence that.
No.
Thanks, David!
Also thanks to Thomas Holtz: I read your notes and corrected some misimpressions (found out arthropods are protostomes but couldn’t apologize for the error before David called that out here) and learned some new things…and got new sources to go peruse.
Thanks again, both of you!
How important was the role of mitochondria in the origin of complex multicellular life?
Assuming this timeline is considered reasonably accurate, it seems that simple unicellular life developed pretty much as soon as the conditions on Earth made it possible. However, it takes another 2+ billion years for multicellular life to occur.
If the inclusion of mitochondria into eukaryote cells was a major contributing factor, then multicellular organisms are primarily a result of a random endosymbiosis event.
This suggests to me that (unicellular) life may be very common in the universe; but complex macroscopic organisms would likely be incredibly rare…
@ David Marjanović
Thanks!
I think that independent origins of animal-like multicellularity would be very recognizable. If there was some obscure worm that turned out closest to ciliates or apicomplexans or rhizarians or excavates, then that would be a clear case. One would recognize that with molecular-phylogeny tools, something that has already resolved several relationships.
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It’s like how oomycetes are nowadays classified in Stramenopiles instead of in Fungi, despite their fungus-like habit. They are closer to diatoms and kelp and the like than “true” fungi.
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There are also the oodles of molecular-level homologies of genes involved in animal development, and PZ has blogged on some of these every now and then. That also points to a single origin for all but the most basal metazoans, like sponges and placozoans, and even there, molecular-phylogeny evidence is consistent with a single origin of animal multicellularity.
Brony: my understanding is that the mineralogy and fabric of at least part of cap carbonate sequences strongly favors an abotic origin. That said, these sequences definitely include biogenic structures: http://web.mit.edu/perron/www/files/Bosak13.pdf
Kagato,
Mitochondria are very important, but the complex climate/atmosphere changes just before the Cambrian (which in turn are connected to changes in the biosphere) results in a chicken-and-egg situation:
Was the rise of oxygen the result of complex algae? Was the lower temperature the result of one or several factors, like increased ? Mitochondria and chloroplasts were probably essential somehwere in the chain of events, but was there additional factors that were required? Had the continents to grow to a specific fraction of the Earth’s surface to speed up chemical weathering? There are a million questions and I am certainly not competent to answer them.
@ Thomas Holtz
I’ll remain interested and keep try to keep disagreements in the field in mind then. The ultimate origins of brain evolution are something I’m very interested in. Calcium signalling is a big part of that (but by no means the only part). How and why calcium signalling was used by evolution in that picture is something I have tried to read about with the experience I have had.
Thanks.
The things that make good headlines such as ‘These findings contradict what scientists long held to be true. . . .’ or ‘Contrary to previous theories. . . .’ seem to engender mistrust and misunderstanding of the scientific process. Journalists doing a fast story often (and even unintentionally) get the science wrong. Scientific views change based upon accumulation of evidence. These types of headlines, of themselves feed into the perception of scientists always being wrong (and so cannot be trusted) or, because scientists get it wrong so often, a non-scientist could do at least as well- after all, we’re only talking about theories.
Sorry to hear of the disappearance of the Hallettstonian Sea Zorias (video).