Why some primates have even tougher births than humans

Scientists have long believed that human childbirth is uniquely difficult among primates—a consequence of our large brains and upright posture. But new research challenges that assumption. Per the Conversation, a study using three-D scans of twenty-nine primate species found that squirrel monkeys and tamarins actually face even tighter squeezes, with babies' heads roughly double the size of the maternal pelvic canal. These primates have evolved remarkable adaptations: some experience temporary pelvic bone dislocation during labor, while others give birth face-first rather than head-first, reducing the space required. Humans can't adopt these strategies—our upright posture means our pelvis must stay rigid for stability—so instead, our babies have evolved highly plastic skulls that mold to fit through the birth canal as they pass. What appears impossible across the primate family tree simply required a different solution.

Listen to this story

Hear this and more stories in a personalized audio briefing.

Open The Chonkerton