Scientists have pinpointed three genes that may have played a pivotal role in the evolution of the striking increase in brain size that helped define what it means to be human.
These genes, found only in people, appeared between 3 and 4 million years ago, just prior to a period when the fossil record demonstrates a dramatic brain enlargement in ancestral species in the human lineage, researchers said on Thursday.
The three nearly identical genes, as well as a fourth nonfunctional one, are called NOTCH2NL genes. They are from a family of genes that date back hundreds of millions of years and are heavily involved in embryonic development.