Cooperative babysitting is likely the reason humans have both massive brains and childhoods that last for decades.
April 24, 2026
Original Paper
Cooperative care as a candidate mechanism linking prolonged childhood and brain expansion in human evolution
PsyArXiv · mr4sp_v1
The Takeaway
Biological rules usually dictate that larger brains require faster development to ensure the species survives to reproduce. Evolutionary simulations show that alloparenting, where community members help raise children, broke this rule for humans. This social shift allowed our ancestors to invest in slow, high quality brain growth without the mother shouldering the entire energy burden. The help of grandmothers and neighbors effectively decoupled brain size from maturation speed. This suggests that our intelligence is a direct product of our social cooperation rather than just genetic luck.
From the abstract
Two traits distinguish modern humans from all other primates: an exceptionally large brain and an exceptionally prolonged childhood. What mechanism produced this combination, and why are the two traits dissociated in other hominins? Standard models predict that brain size and developmental duration should co-vary tightly, yet the fossil record reveals that they do not: small-brained hominins at Dikika, Dmanisi, and Rising Star show slow development, while large-brained Neanderthals matured fast.