Tracking back to acceleranistas16 Dec 2007
I've had a very busy couple of days, and haven't been maintaining my reading-and-linking as much as I had hoped. So I wanted to take a few minutes to do a quick tour of the blogosphere to see what people are saying about the idea of acceleration.
I'm linking to posts I have read, and in some cases commented on. They are a mix of explanation of the concepts, applauding the ideas and analysis, and criticism of the methods. What I most want to point out is that the discussion on blogs is at a very high level -- people are reading the paper with much more precision than I have ever experienced in the peer review process. This is really the best that today's science community has to offer.
One of the best posts is over at LiveJournal, where shoshin works through the theoretical part of the paper. Naturally, this is my favorite part -- and shoshin describes things exceptionally well. The beginning is great:
The case for a recent acceleration of human evolution in the last 40K years (and especially the last 10K) follows pretty straightforwardly from evolutionary first principles combined with elementary facts about human history since the late Pleistocene. So straightforwardly, in fact, that you have to wonder why nobody thought of it sooner. It's one of those rare cases where the theoretical argument is so strong that you can pretty much use accordance with it as a test of experimental methods at least as much as the other way around.
Razib works through the paper at Gene Expression, in a long, detailed post. I like this part:
We are now the most numerous large mammal on the face of this planet. Using the data above the authors imply that our species has been subject to somewhat more that 1/2 a substitution per year. Remember, a substitution is a replacement of one allele for another at a locus on a population wide scale. If this is correct that means right now every few years alleles driven by selection are being fixed within our species.
At the old-school Gene Expression, p-ter posts some analysis and critiques. A great comments section has arisen on this post, including comments from some of the principals, and general comments about the quality of the discussion on blogs compared to the journal process. I've answered some of the points in my rarely asked questions post, but the most powerful part bears repeating:
Every distribution has a tail, so if they were to move their threshold a bit further to the right, surely they'd be able to narrow down the number of regions to something consistent with a constant rate. That is, the entire argument is predicated on perfectly identifying selection in the regions of the parameter space they search. This is a major assumption, and not one I'm willing to make without strong evidence. They provide none.
Actually, with an acceleration of around two orders of magnitude, we can tolerate a lot of slop in the estimates. We don't need to perfectly identify selection -- in fact, we'd still have strong support for rapid acceleration if we threw away 95 percent of our data! Naturally, we don't have to do that -- our methods are based on a threshold that eliminates nearly all false positives, and we are missing the vast majority of events. For one thing, the LDD test doesn't find selection on multiple alleles at the same locus. I am working on new methods that will find some of these kinds of events, but for the time being we continue to interpret all things conservatively.
Andrew Sullivan posts approvingly:
I posted on this potentially world-changing research this afternoon. Here's a helpful, chatty, specialist blog with lots of extra links if you're scientifically literate and curious.
What I want to know is, sure, Razib is helpful and chatty, but what am I, chopped liver?
Larry Moran has added several posts on the research, starting with this one:
In addition to the major flaw in logic, there are many other things wrong with the claim that modern humans have stopped evolving. The claim carries with it a very loaded assumption that is never explicitly stated. The assumption is that humans have pretty much reached their optimal level of fitness for all other characteristics. For example, we are no longer selecting for higher intelligence, or a better immune system, or more efficient energy production, or stronger muscles, or any of a host of other things that might make us better adapted to all environments.
Why is this assumption necessary? Because nobody could possibly suggest that we have stopped evolving without assuming that we have reached optimal fitness for all those things in our present environment.
Larry follows with several other posts, some critical, focused in part on the problem of how much evolution is explained by positive selection as opposed to other forces.
Nature's blog, "The Great Beyond" notes the paper and the resulting discussion.
More will follow...