When reasoning about why humans feel loneliness, don’t only think about the human ancestral environment. Mice feel lonely too!
The mechanisms that mammals and birds use for emotions around loneliness probably evolved, 325-500 million years ago. However, there are plenty of mammals and birds that evolve to be solitary and are thus unlikely to feel loneliness.
If you look farther back in evolutionary history, it tells you about how the basic mechanisms work but different species turned those mechanisms quite differently.
If something is stable against mutations over the last million years it either needs to be deeply interlinked with other mechanisms or it needs to be produce a survival advantage that prevents mutations from deleting it.
I was surprised to find out that I could not find a single neurotransmitter that is not shared between humans and mice (let me know if you can find one, though). An example of interfaces as a scarce resource?
It’s easier to have mutations that mean that a neurotransmitter is produced in a new context or that a receptor to a neutrotransmitter does something new than having both a newly produced neurotransmitter and new receptors at the same time.
Mice (and rodents in general) don’t have β‑MSH.
Maybe this is just part of a larger machinery where your nervous system hands out a reward when you satisfy a strong urge (homeostatic feedback control circuit) back to homeostasis?
I would think that’s part of the explanation. It’s also worth noting that peeing is a bodily process that comes with the need to relax parts of the body that otherwise usually aren’t relaxed. Relaxation can feel rewarding even if the rewarding feeling is not the purpose.
The mechanisms that mammals and birds use for emotions around loneliness probably evolved, 325-500 million years ago. However, there are plenty of mammals and birds that evolve to be solitary and are thus unlikely to feel loneliness.
If you look farther back in evolutionary history, it tells you about how the basic mechanisms work but different species turned those mechanisms quite differently.
If something is stable against mutations over the last million years it either needs to be deeply interlinked with other mechanisms or it needs to be produce a survival advantage that prevents mutations from deleting it.
It’s easier to have mutations that mean that a neurotransmitter is produced in a new context or that a receptor to a neutrotransmitter does something new than having both a newly produced neurotransmitter and new receptors at the same time.
Mice (and rodents in general) don’t have β‑MSH.
I would think that’s part of the explanation. It’s also worth noting that peeing is a bodily process that comes with the need to relax parts of the body that otherwise usually aren’t relaxed. Relaxation can feel rewarding even if the rewarding feeling is not the purpose.