There are only two changes in the 118 letters of DNA code that make up HAR1 between the genomes of chimps and chickens. But chimps and humans are 18 letter-changes apart. And those mutations occurred in just five million years, as we evolved from our shared ancestor.It's important to note that it's not the only significant difference between chimps and humans. Chimps are better dressed, and never backstab their cinematic costars.
“That is an incredible amount of change to have happened in a few million years,” Pollard notes.
Subsequent experiments looking at the brains of human and primate embryos revealed that HAR1 is part of two overlapping genes. One of these genes, called HAR1F is active in nerve cells that appear early in embryonic development and play a critical role in the formation of the layered structure of the human cerebral cortex.
The role of the other gene, called HAR1R, is less clear, but it also appears also to be involved in cortex development.
Aug 17, 2006
bigger, smarter brains from two genes?
A new kind of gene, a surprising rate of mutation, and a critical area of cortical development converge in this week's genomic revelation.