First hominid’s rewired brain
A computer-generated cast of the inner surface of a 7-million-year-old cranium, which bears impressions once made by brain features, suggests that hominid evolution kicked off with big neural changes. The skull, unearthed in Africa in 2001, belongs to Sahelanthropus tchadensis, a species controversially proposed as the earliest known member of the human evolutionary family.
X-rays enabled a research team to see through Sahelanthropus’ rock-filled cranium and reconstruct its brain surface. That 3-D reconstruction of the ancient creature’s brain terrain reveals a hominidlike setup, said Thibaut Bienvenu of the University of Poitiers, France, on April 12. Shapes of the front and back of Sahelanthropus’ brain, as well as the tilt of its brain stem, matched corresponding brain measures for 2- to 4-million-year-old hominids and modern humans.
An upright posture and two-legged gait stimulated neural reworking in Sahelanthropus, Bienvenu speculated, even though the hominid’s brain was about one-quarter the size of people’s brains today.