"Australopithecus" possessed two of three duplicated genes derived from "SRGAP2" roughly 3.4 and 2.4 million years ago ("SRGAP2B" and "SRGAP2C"), the second of which contributed to the increase in number and migration of neurons in the human brain.Significant changes to the hand first appear in the fossil record of later "A. afarensis" about 3 million years ago (fingers shortened relative to thumb and changes to the joints between the index finger and the trapezium and capitate).