This gene is one of the 23 genes that are duplicated in humans but not in other primates.
This protein in humans has been duplicated three times in the human genome in the past 3.4 million years: one duplication 3.4 million years ago (mya) called SRGAP2B, a second duplication 2.4 mya (called SRGAP2C), and one final duplication ~1 mya (SRGAP2D). The ancestral gene SRGAP2 is found in all mammals and the human copy has been renamed SRGAP2A. The 2.4 million year-old duplication (SRGAP2C) expresses a shortened version that 100% of humans possess. This shortened version SRGAP2C inhibits the function of the ancestral copy SRGAP2A and (1) allows faster migration of neurons by interfering with filopodia production and (2) slows the rate of synaptic maturation and increases the density of synapses in the cerebral cortex.
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