Were fast-evolving stretches of DNA crucial to human evolution?
|November 14, 2013||Posted by News under Human evolution, News|
“In this study, we found stretches of DNA that evolved much more quickly than others. We believe that these fast-evolving stretches were crucial to our human ancestors becoming distinct from our closest primate relatives.”
These stretches are called human accelerated regions, or HARs, so-called because they mutate at a relatively fast rate. In addition, the majority of HARs don’t appear to encode specific genes. The research team hypothesized that HARs instead acted as “enhancers,” controlling when and for how long certain genes were switched on during embryonic development.
Through experiments in embryonic animal models, combined with powerful computational genomics analyses, the research team identified more than 2,600 HARs. Then, they created a program called EnhancerFinder to whittle down that list to just the HARs were likely to be enhancers.
Almost like it was a program or something.
Additional analyses revealed five such HARs, which were active in both human and chimpanzee genomes, but which activated genes in different embryonic regions. For example, the human versions of HARs 2xHAR.164 and 2xHAR.170 are active in a region of the brain between the midbrain and hindbrain, while the chimp versions are not. This so-called “gain of function” of these two HARs in human embryos may point to differences in the development of key brain regions such as the cerebellum, which is known to regulate not only motor control but may also regulate higher cognitive functions, such as language, fear and pleasure.
Oh, wait. Program, my foot! There’s no reason to think it didn’t all just happen that way due to random mutation. After all, as neurosurgeons know, the brain is precisely the sort of organ that can just be messed around, with little impact.
“These results, while preliminary, offer an unprecedented glimpse into how very recent changes to the human genome have modified the genetic programs that control embryonic development to potentially yield different results,” said Dr. Capra. “We anticipate that if we were to look at the activity of HARs that are enhancers during later developmental stages, we would see even more differences between humans and chimpanzees.”
What? Differences? Call the 99% chimpanzee squad!* Dr. Capra is confused; he does not know what he is saying.
Seriously, though, watch this file. These people could possibly be on to something (whatever it turns out to be).
They are much more likely to be on to something, at any rate, than the crowd who are still trying to convince us that chimps “really” think like people in all sorts of ways—if you would please just imagine them doing it hard enough.
* If we have to, we will settle for the 98% chimpanzee squad. One must make some concessions to reality, after all.