If both parties have a stake in the other, the chances of them killing each other are going to be reduced.

Future benefits rarely figure in the minds of animals.

Octopuses have hundreds of suckers, each one equipped with its own ganglion with thousands of neurons. These 'mini-brains' are interconnected, making for a widely distributed nervous system. That is why a severed octopus arm may crawl on its own and even pick up food.

There's actually a lot of evidence in primates and other animals that they return favors.

The thinking is that we started evolving language not by speaking but by gesturing.

As in a Russian doll, however, the outer layers always contain an inner core. Instead of evolution having replaced simpler forms of empathy with more advanced ones, the latter are merely elaborations on the former and remain dependent on them. This also means that empathy comes naturally to us. It is not something we only learn later in life, or that is culturally constructed.

I've argued that many of what philosophers call moral sentiments can be seen in other species. In chimpanzees and other animals, you see examples of sympathy, empathy, reciprocity, a willingness to follow social rules. Dogs are a good example of a species that have and obey social rules; that's why we like them so much, even though they're large carnivores.