Myth: multicellular life arose in the Cambrian


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.

More like this

Scanning electron photomicrographs of two fossil embryo specimens from the 600-million-year-old Doushantuo Formation in South China. From EurekaAlert: A decade ago, Shuhai Xiao, associate professor of geosciences at Virginia Tech, and his colleagues discovered thousands of 600-million-year-old…
Some of the biggest misunderstandings about the evolution of life on earth surround the "Cambrian Explosion," the popular impression often being that complex multicellular life sprung up out of nowhere in an instant. While it does appear that there was an "explosion" and that new body plans…
I've been reading Valentine's On the Origin of Phyla(amzn/b&n/abe/pwll) lately, and I have to tell you, it's a hard slog. This is one of those extremely information-dense science texts that rather gracelessly hammers you with the data and difficult concepts on page after page. I am convinced…
So what do you see? A groove and some lines? Truth be told, this is possibly the oldest recorded chordate fossil (or, should I say, one of a number of seventeen specimens of same). It dates from the pre-Cambrian - i.e. before 543 million years ago - during a period known as the Ediacarian. Found by…

I completely agree with your overall conclusions, but I'm not sure I agree with your late-intermediate discussion.

The claim from genetic clocks for metazoan LCAs predating the Ediacaran was controversial when they were published, and are still controversial. The problem is that those clocks contradict, by a large margin, the existing fossil evidence.

I am not familiar with any supported evidence for metazoan fossils (even microfossils) as old as 700 Mya, even though there are lagerstatte of that age where they could (should?) be preserved. There are some Ediacarans which seem more like early cnidarians, which certainly supports a Precambrian origin.

The extant fossil data surely supports a relatively late diversification of arthropods, chordates, et al., circa 550-600 Mya, assuming that the Ediacarans are an independent evolution.

Of course, and fully supporting your thesis -- "late diversification" doesn't mean "sudden" or "miraculous" (gack, cough, choke...).

By Michael Kelsey (not verified) on 27 Sep 2014 #permalink

Doesn't everyone know that the "Cambrian explosion" was in animals amenable to fossilization? And those critters are highly unlikely to have appeared miraculously, then, as now, there were a lot of animals unlikely to fossilize, had to have gone back a long ways, as exoskeletons don't evolve in a day. And if I, a HS grad know this, WTH are they teaching liberal arts kids these days?

Michael, you may want to look at'the Cambrian explosion: the construction of animal biodiversity' by Douglas and Valentine. Covers what we know, largely (but not solely) from a molecular genetics perspective. It certainly pushes the timeline back.

@Stewart #4: Thanks! If Jim Valentine is one of the authors, I'd expect it to be pretty solid. I'm relatively familiar with the current consensus, in particular the assumption of the metazoan basal clade being something like a choanoflagellate around 650 Mya.

I'm just not sure that the "molecular clock" argument deserves to be given primacy -- the model is a bit too simplistic, in my view.

By Michael Kelsey (not verified) on 28 Sep 2014 #permalink

I wonder if I am still banned from this list

By Intelligent Designer (not verified) on 01 Oct 2014 #permalink

You're not – and it's not a list, it's a blog...

By David Marjanović (not verified) on 01 Oct 2014 #permalink