MCPH1 (microcephalin 1)

MCPH-1 is a DNA damage response protein. Inactivation of the MCPH1 gene in humans results in a severe condition called microcephaly, i.e. a small brain, associated with mental retardation. As human evolution is characterized by a marked increases in brain size, one group evaulated this gene and reported that it had undergone significantly higher rates of protein sequence evolution in primates than in rodents. Furthermore, they reported that the gene has undergone even more rapid evolution in humans, including evidence of a selective sweep in human populations. However, several aspects of the latter findings have been debated by other groups. Regardless, it is interesting that a gene that is associated with a small brain when it is damaged in humans, may have also shown increased evolution in humans.