Because that’s where our brains are and it’s in our brains that all of that happens.
But before people really knew what the brain was/does, did they think of their thoughts in that way, or did they think that thoughts came from elsewhere, maybe whizzing about their whole bodies? Or is it natural to place thoughts in the head because that’s where most of the senses are based?
i imagine that we probably knew that the mad thing in our head was where our thoughts were not long after we started torturing rivals and figured out we could basically dismember someone entirely and they’d still be thinking and that, but if you cut their head off it’d be all over.
the male argonaut octopus doesn’t technically have a penis. It has a detachable limb that it can send out covered in sperm to float towards a female in order to fertilise her. it is believed the main reason for this to have evolved is because the female argonaut is around 5 times the size of the male and incredibly aggressive, being known to strangle and devour males who come too close when attempting to mate.