MCPH1 is expressed in the fetal brain, in the developing forebrain, and on the walls of the lateral ventricles. Cells of this area divide, producing neurons that migrate to eventually form the cerebral cortex.

A derived form of MCPH1 called haplogroup D appeared about 37,000 years ago (any time between 14,000 and 60,000 years ago) and has spread to become the most common form of microcephalin throughout the world except Sub-Saharan Africa; this rapid spread suggests a selective sweep.[13][14] However, scientists have not identified the evolutionary pressures that may have caused the spread of these mutations.[15] This variant of the gene is thought to contribute to increased brain volume.[16] Modern distributions of chromosomes bearing the ancestral forms of MCPH1 and ASPM are correlated with the incidence of tonal languages, but the nature of this relationship is far from clear.[17]

https://en.wikipedia.org/wiki/Microcephalin

(http://www.autoadmit.com/thread.php?thread_id=3946859&forum_id=2#35822281)

"Haplogroup D may have originated from a lineage separated from modern humans approximately 1.1 million years ago and later introgressed into humans. This finding supports the possibility of admixture between modern humans and extinct Homo spp. While Neanderthals have been suggested as the possible source of this haplotype, the haplotype was not found in the individuals used to prepare the first draft of the Neanderthal genome."

(http://www.autoadmit.com/thread.php?thread_id=3946859&forum_id=2#35822527)