[endymi0n]

So how evolution works is that a feature needs to have an evolutionary advantage, but the specimen must also not die. So there are two adversarial pressures here, carefully balancing each other in a mammal species that already has one of the highest birth mortality rates of both mother and child. If heads were any larger, it would create a proportional amount of negative evolutionary pressure by both direct and indirect death (of the mother) at birth.

Interestingly, there seem to be some indications showing that human interventions by modern technology already show clear evolutionary trends: https://pmc.ncbi.nlm.nih.gov/articles/PMC5338417/

Humans might eventually evolve to not even being able to be born naturally anymore at some point.

[Alex-Programs]

That's a fascinating thought. As people with larger brains are more successful in life and more likely to have children*, mortality rates for natural births would increase, and over time we would evolve to become dependent upon modern technology.

The continued existence of our species would become dependent upon continued civilisation. A dark age could kill us, or at least cripple the population.

*how true is this? Uni-educated people tend to have lower fertility rates.

[mmooss]

> As people with larger brains are more successful in life and more likely to have children*

> *how true is this? Uni-educated people tend to have lower fertility rates.

In the U.S. university education depends mostly on mommy and daddy's wallet size, not brain size.

[kridsdale3]

"Children? With these economic conditions?"

[barnabyjones]

If maternal mortality were the only issue, evolutionary pressure would also favor women with wider hips/birthing canals. After all, we see hyper intelligent individuals at the current brain size, it's clearly possible to get more processing power in there but there doesn't seem to be much reproductive benefit.