E-I-E-I-O in Old McDarwin’s Animal Farm
One would think that if all animals are related according to Darwin’s theory of common descent, this should be clearly evident in the genes. It would also seem that the more genomes we sequence, the clearer the evolutionary pattern should be. At least that’s how Raible and Arendt lay their foundation in a paper in the Feb. 3 issue of Current Biology:1
It is a truism that the plausibility of an evolutionary inference increases with the amount of data on which it is based, and the ever-quickening provision of full genome sequences is providing a huge amount of grist for the evolutionary biologist’s mill.
Ah, but that would make for a predictable plot if no conflict were inserted. The thrust of their paper is that comparative genomics has produced many evolutionary surprises. Particularly, humans share some genes with the earliest metazoans that are not present in fruit flies, worms, and other branches of more advanced metazoans. In one study, those groups have lost 10% of early metazoan genes while humans have only lost 1%. They cite several studies with similar findings. Somehow, humans have retained many genes that other groups have lost. We seem to have more in common with flatworms than fruit flies in terms of retained genes.
The authors take up another truism: “Genes do not evolve on hold: whenever a gene appeared on the animal evolutionary tree, it was functional. This ancestral function should be close to the consensus function present in today’s animals that have retained that gene.” In other words, the genes we retain from earliest ancestors have had to function all that time, not wait for us to appear and decide to use them in recent times.
In their analysis of several “striking” studies on the branch that led to us, the authors conclude that advanced functions appeared early, and remained intact for many millions of years, during which time other advanced organisms managed to get by without those functions. “These findings imply that the Urbilateria [earliest ancestors] were genetically more complex than previously thought to be the case.” Elsewhere they say, “Taken together, these new analyses of gene loss frequencies and of sequence divergences suggest that the human genome – and thus those of the entire vertebrate lineage – has diverged much less from the ancestral genome of our urbilaterian ancestors than have the Drosophila and C. elegans [roundworm] genomes.” This can only mean, in their thinking, that the fly and worm lines learned how to evolve a lot faster than the vertebrate line.
Even more striking is the similarity between Darwin and George Orwell:
Vertebrates, lophotrochozoans and anthozoans are a good choice for such comparative evolutionary research, because they appear to share a surprisingly large part of the ancestral gene inventory that has been lost in other groups. In a certain sense, therefore, these animals, like some of those on Orwell’s Animal Farm, are more equal than others, and thus should be most revealing about our complex past.
1Florian Raible and Detlev Arendt, “Metazoan Evolution: Some Animals Are More Equal than Others,” Current Biology Vol 14, R106-R108, 3 February 2004.
We beg to differ with their opening truism. Based on our empirical research, reading hundreds of papers on evolution, the amount of actual data available for study is inversely proportional to the amount and credibility of Darwinian storytelling (see 11/16/2002 entry and the following story, for instance). Their truism is a mythoid.
These authors seem to feel that if the data don’t fit, they really ought to (see quote, top right box). One thing we have learned about this Animal Farm. The pigs are the members of the Darwin Party. They rewrote the constitution of science (see 12/22/03 commentary) to keep themselves in power, because some beliefs about origins are more equal than others.