Just a few brief comments regarding chapter 2. I think my other comments I was planning to make on the chapter would do better within the third chapter. The first is a story probably many of you read today on recent evolution of the human brain. (Here's two accounts, one at Newsday and the other at The Washington Post) The most interesting one is a mutation, in about 30% of the world's population that affected brain size and showed up only 6,000 years ago. The other mutation affecting 70% of the world population occurred 37,000 years ago. Given that Tomasello's thesis deals with the development of human society but is also problematized by the time issue of development, these studies are particularly interesting.
Allow me to quote from the Newday story.
"We don't know what these new variants do," Lahn said. "But they might confer a selective advantage by improving cognitive abilities. This needs to be confirmed."
The scientists estimate the first sightings of these genes by calculating the slight differences among individuals in the populations studied. Lahn likens it to the vast array of Bibles that probably descended from a single copy. Over time, revisions can lead to errors or intentional changes in the content. The scientists assume a certain rate of change over time, and that is how they find their way to the ancestral gene.
While the first modern humans date back 200,000 years ago, our closest human ancestors, ones with shared human behavior, probably evolved around 40,000 years ago, Harpending said.
People with damage to either of these two genes -- microencephalin and ASPM -- have smaller brains, equal in size to chimp brains. They also suffer from impaired cognitive abilities and have severe language problems.
Now I'm not sure where Lahn is getting that 40,000 year figure from. It seems a somewhat safe bet, although the figure could go back as far as 200,000 years if Tomasello's thesis is right. (Although given his thesis and the time problem, it's hard to see how it would work even with a date of 40,000 years)
Obviously it's far too early to discern much from this, since the role of the genes isn't known yet. It would be nice to know which cognitive abilities are impaired, for instance. Is this related to a form of autism? If so, then this would offer some support for Tomasello's thesis. Certainly the connection to language is intriguing.
What would be interesting is to introduce the mutation in non-human primates and see what effect it brings. (Anyone remember the premise behind Planet of the Apes?) It seems to me though that this offers many ways to test both Tomasello's thesis as well as variations to it. (Such as my thought that perhaps multiple cognitive centers are involved)
Just a note that I have up a page listing all the blog posts that are part of the reading club. It's also in my right sidebar in the archive area as Reading Tomasello. If you aren't a member of the club but have a post at your blog on this book, please post a note there with a link.
Just to add some caution on the above data ought be kept in mind. From the WaPo report:
That the genetic changes have anything to do with brain size or intelligence "is totally unproven and potentially dangerous territory to get into with such sketchy data," stressed Dr. Francis Collins, director of the National Human Genome Research Institute.
Aside from not knowing what the gene variants actually do, no one knows how precise the model Lahn used to date them is, Collins added.
Lahn's own calculations acknowledge that the microcephalin variant could have arisen anywhere from 14,000 to 60,000 years ago, and that the uncertainty about the ASPM variant ranged from 500 to 14,000 years ago.
That uncertainty in date is relevant to the Tomasello discussion as well obviously.
There are some extensive links related to the above, along with scientific papers here. (HT: Razib)
Razib says that this new claim is the result of a long line of research. So while it is tentative, it's not coming out of the blue. Check out the papers.
Also check out John Hawks' comments.
I've closed comments in order to avoid spam since I don't check this older blog as much anymore.
and Theology
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