As a student, Trivers would sometimes work until three in the morning. “So at one thirty, I would hear some ‘woo hoo-hoo,’ and I would see, ha ha! What happened is the male has fallen asleep and the female has crept back down to the comfortable position, which is how she would prefer to sleep the night. He wakes up and sees she is there, and pecks her back up into this uncomfortable position!” he says. “The sexual insecurity or the risk of an extra-pair copulation is strong enough to make me willing to inflict a cost on my mate.”
Trivers is not making himself look like a good partner lol. Also, single beds are impossible to be comfortable for two people at once unless they are throughly wrapped around each other so it just makes sense for people to attempt to get comfortable at the expense of their bedmate
