Most people understand how selfishness and competition drive evolution. But if that's the case, why do we make friends at all? This video essay from New Scientist's MacGregor Campbell offers a quick and informative answer to that question.

First of all, humans aren't the only animals that form friendships, so scientists have been able to study how friendships work in a variety of creatures from elephants to dolphins. What all these creatures share is a social system of intimate connections that have helped them survive as a species. Animals that form friendship bonds are able to get more food, and rear their young more safely. That means healthier babies — and more adults.

One of the interesting topics that MacGregor tackles in this video is the correlation between animal intelligence and friendship formation. Certainly not all intelligent animals are social — octopuses are relentlessly solitary, and there is plenty of evidence that they are scary-smart. But primates, dolphins, and other friend-makers do seem to need a lot of mental processing power to keep track of friendships, as well as their friends relationships with each other.

The point here is that altruism and friendship may be key to species survival — perhaps more than we ever realized.