Why are humans so aberrant - that is to say - why do all human cultures have marriage-like institutions while 90 percent of mammalian species are promiscuous?
The neuroscientist David Linden points to our "jellyfish-like or coral-like" neurons, which are pretty crummy parts if you are trying to create "clever us."
These ancient, inefficient neurons "signal probabilistically, they are unreliable, they leak signals to their neighbors and they're slow," Linden says. And so, in order to be clever humans, we need an extraordinarily large number of neurons and a huge brain to store them all. And that, in turn, means that it takes humans, as opposed to orangutans, an extraordinary amount of time to develop.
This long post-natal maturation - the longest childhood of any animal - means that "single moms aren't very effective in keeping their children alive in hunter/gatherer societies," Linden says. And that is why love is so important for human survival.
Directed / Produced by Jonathan Fowler, Elizabeth Rodd, and Dillon Fitton