…Or rather why did Mark interpret this information that way? I know, I know, rhetorical question, to some extent. I don’t think that we are yet at a stage of comparing genetic sequences to say one organism is more evolved than the other. But Mark Henderson, ‘Science Editor’ of the newspaper
..Comparison of the genomes of the two [humans & chimpanzees] has revealed that many more chimp genes than human ones have been the subject of positive evolutionary selection….
….Chimpanzees have evolved more extensively than humans since the two species split from their common ancestors.
[And this refutes the] anthropocentric view that a grand enhancement in Darwinian selection underlies human origins.”
This conclusion is horribly misleading, and I want to clarify that the number of genes that have been positively selected for, is not the primary mode for evolutionary change. Positive selection sometimes manifests itself in copy number variations, or genes within a genome that have been repeated in order to increase the frequency that transcript will be made. That is what the authors of the original paper compared. But, it is where these changes, duplications for example, are made that ultimately facilitate evolutionary change.
If you are still a bit confused let me try and make a more descriptive explanation. The best analogy that I can come up with right now is that a chimp could have 200 pennies in its hand. That’s $2.00. Some would consider me a human, and I would conversely have 20 dimes in my hand, but that’s also $2.00. The same concept applies with the number of positive selection features within a genome. It’s not how many positive selection artifacts one has, but what one has and where is it in a genome.
In another light, chimps have evolved in a much different time frame and continue to evolve in a much different environment, compared to humans. Different selective pressures may affect more genes being modified in a chimpanzee genome, than one in a human one because we are fundamentally different when looked down to the chromosomal level. So how could we fully compare something like this?
What is so ironic, is that Henderson goes to quote the authors of the paper he is reporting on,
“The study… underlines that evolution is not a matter of progress towards a goal, and that it is incorrect to assume that more intelligent species are “more evolved”.”
So why has he and the editors of The Times published the article with the title that chimps are winning this evolutionary race?
I don’t know. I don’t think anyone knows really. There’s no race! If anyone is ‘winning the evolutionary race’ it is humans, we are unfortunately decimating chimpanzees. But enough ranting. I will hold out to see what the official publication concludes, once its out. All I know is that it will be published in PNAS under the title and link, “More genes underwent positive selection in chimpanzee evolution than in human evolution.”
If you wanna read more about genomic comparisons between humans and other papers, I’ve written a lot about recent papers that discussed this topic. It should be noted that in these recent papers, different conclusions were made from the ones that Henderson is reporting on. So that maybe of interest to you. Here’s a list of links:
- Mapping out recent evolution on the human genome.
- A new study of copy number variation in chimpanzee genome.
- The contribution of Copy Number Variations (CNV) to human genetic variation.
- Identifying the characteristics of the Fastest Evolving Regions of the Human Genome.
Oh yes, how could we have a discussion of genome comparisons of primates without linking up John Hawks? He also writes about positive selection in human-chimpanzee genome comparisons.
Hat tip to Razib, for linking up this article and starting the fire.