Our ancestors’ prenatal growth sped up after we split from chimps

High prenatal growth rates found in modern people may have first evolved in ancient hominids less than a million years ago, according to estimates based on fossil teeth.

Human fetuses grow by around 11.6 grams per day on average – considerably faster than the fetuses of gorillas, the next fastest ape in the hominid family, with a rate of 8.2 grams per day.

“We found that human-like gestation [may have] preceded the evolution of the [modern human] species – around 200,000 to 300,000 years ago – and may in fact be a critical factor that led to our evolution, particularly our large brains,” says Tesla Monson at Western Washington University.