system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: Why do pretty much every mammal’s breast retract when they’re not needed but its not the case for humans ?
gpt
One explanation is that prominent breasts, concealed ovulation, lower sexual dimorphism,  reduced canines, hands, intelligence and reduced male competition are co-evolved features. The first two confuse dominant males about sexual receptiveness (in most primates enlarged breasts signal pregnancy, hence non-fertile). This lowers male competition (lower dimorphism and reduced canines), and directs it to provisioning (bringing food to females in exchange for sex) - hence hands and intelligence. Which then lead to enhanced sociality, which fosters group bonding, reduced intra-group competition and more intelligence as social factors come to the fore.

As a theory, it fits. It needs more evidence, though.