Armies are a purely human invention. Most soldiers who go to war nowadays don't even do it because they're inherently aggressive.

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.

As far as the environment is concerned, I am becoming pessimistic because I do not see anybody stepping up and taking the long view approach. It seems like we're stuck in a tragedy of the commons where everyone is trying to contribute as little as possible to get out of this situation.

I have often noticed how primate groups in their entirety enter a similar mood. All of a sudden, all of them are playful, hopping around. Or all of them are grumpy. Or all of them are sleepy and settle down. In such cases, the mood contagion serves the function of synchronizing activities.

Humans became easy prey when they moved from the forest to the savanna, which deprived them of the option of climbing trees to flee predators. This shift made it necessary for the men to actively protect the women and their babies. Only as a result of this protection were women able to give birth in shorter intervals, perhaps once every two or three years. This meant that they could produce offspring about twice as frequently as apes. I would be willing to bet that this rapid reproduction is one of the reasons why we dominate the world today, and not the apes.

To endow animals with human emotions has long been a scientific taboo. But if we do not, we risk missing something fundamental, about both animals and us.

I am personally not against keeping animals at zoos, as they serve a huge educational purpose, but treating them well and with respect seems the least we could do, and with 'we' I mean not just zoo staff, but most certainly also the public.