A Chinese-American team may have discovered, if not a “Precambrian rabbit,” the next best thing: Precambrian embryonic fossils showing the kind of development only multicellular organisms show. The team leaders do not know whether they found an early plant or animal. But their find, if it holds, threatens to shake the foundations of biological evolution.
What the team found
The team members come from Virginia Polytechnic Institute and State University (Blacksburg, Va.) and the Chinese Academy of Sciences. Two days ago the journal Nature published their letter. In it they describe their study of spheroidal fossils in a mineral called phosphorite in the Ediacaran Doushantuo Formation in southern China. Five other teams had published their own interpretations of these fossils. The fossils have been under study since 1998. Other teams have suggested they might be “sulphur-oxidizing bacteria, unicellular protists, mesomycetozoean-like (sic) holozoans, green algae akin to Volvox, and blastula embryos of early metazoans or bilaterian animals.” But in the Nature letter of two days ago, the team under Lei Chen and Shuhai Xiao said the earlier teams overlooked something. Lei Chen and Shuhai Xiao found fossils that looked much like late-developing blastulae (an early embryo). In fact they showed evidence that germ cells (for reproduction) and somatic or body cells were already showing the first differences of form one sees in a developing embryo. The team even found evidence of cells programmed to die. This does not happen in one-celled micro-organisms.
The problem: conventional radiometric dating assigns an age of 600 million years to the Ediacaran Doushantuo Formation. But by the same convention, the Cambrian Explosion happened 545 million years ago. In other words, these are Precambrian late-developing embryos.
The on-line magazine Inquisitr covered this story yesterday (September 25). But neither Inquisitr nor the Chen-Xiao team seem to understand how important their discovery is.
A Precambrian rabbit?
The late J. B. S. Haldane once answered the question of what could shake his confidence in conventional biological evolution. Among other things, he said “Precambrian rabbits” would so shake his confidence. Ten years ago, Richard Dawkins admitted, to C. Wallis at Time magazine, that mammalian fossils in Precambrian rocks would “blow evolution out of the water.”
NBC News tried to say this find would strengthen, not weaken, the case for biological evolution. (Or at least, that’s how Inquisitr read the NBC report.) Dr. Xiao suggested these blastula-like fossils could be transitional forms between one-celled life and the earliest animals (or plants). In other words, they are the Missing Links between one-celled and many-celled life. But these are embryos, not fully formed cubs or sprouts or other “young life” forms. To call these “Missing Links” one must bring back the old argument that “ontogeny recapitulates paleontology.” In other words, these blastula-like forms were “adults” once and are embryos today. Remember Ernst Haeckel? He tried to make that argument. He drew what he said were successive stages in the development of human beings. Those stages looked like more “primitive” animals. Except they looked a little too much like those “primitives.” Because Ernst Haeckel fudged the drawings. All authorities acknowledge this today. And that forgery, and the finding out of it, severely weakens the “ontogeny recapitulates paleontology” case.
So Dr. Xiao has not found the Precambrian rabbit. But he has found a Precambrian embryo. No convention of biological evolution can explain this. Xiao almost certainly does not infer all his find implies. But that does not make the find any less important, or less threatening to the evolutionary paradigm.