It is hard to speak of evolution without inadvertently attributing to it intent. I might say, ‘beetles evolved to fly’, which sounds like the beetles had a choice in the matter. Of course they didn’t. Or, I might say, ‘evolution guides us’, or ‘evolution wants us’. No, evolution can’t guide us or want us to do anything; it’s not a sentient entity, it’s a process. I use these expressions because they are a convenient shortcut to refer to the process of natural selection.

We evolved happiness in the same way we evolved our eyes, ears and kidneys. Happiness serves a purpose. Consider the first kind of happiness, pleasure: when we engage in short-term behaviours that benefit us and our species, such as eating, having sex or playing (playing hones our skills), we are immediately rewarded with pleasure. That pleasure is evolution’s way of persuading us to engage in those behaviours.
  We are also rewarded when we engage in beneficial ongoing behaviours. However, ongoing behaviours cannot be rewarded with instantaneous pleasure. But they can be rewarded with a milder, ongoing pleasure: a relaxed, general feeling of wellbeing – core happiness. Core happiness is evolution’s incentive, and reward, for engaging in beneficial ongoing behaviours.
  What would those ongoing behaviours be?
  (1) Living in a tribe is one. In prehistory, hominins* born with an inclination to live in a tribe were more likely to live long enough to pass on their genes. Those who didn’t live in a tribe were more likely to starve or be eaten.
  The inclination to live in a tribe involved the need to contribute to the tribe and feel valued for that contribution. That helped them feel connected. Some people call that need for connection ‘the deep need to belong’. When we engage in behaviours that satisfy that deep need to belong we are rewarded with core happiness. When we don’t satisfy that need we feel isolated and unsettled, even anxious.
  (2) However, although we felt the need to be in a tribe we also had to hunt and keep ourselves fed. With too much anxiety we would be too afraid to leave the safety of the tribe, and we’d starve; with too little anxiety we would take too many risks, and die. To get the right balance we needed to feel frightened in a scary situation yet feel we could handle it. When we achieve that balance we are again rewarded with core happiness.

In summary, we have an innate need to satisfy our deep need to belong, and an innate need to feel we can handle life. When we satisfy those two needs we feel strong and resilient, and we are rewarded with core happiness.
  And, when we don’t satisfy those needs we feel lousy. That’s evolution’s way of prompting us to change the situation.
  There are other long-term innate needs we need to satisfy, but this book is about those two. How can we satisfy them and become resilient? And in turn, happy?
Keep reading!

*  (Hominims are, according to the Australian Museum, “the group consisting of modern humans, extinct human species and all our immediate ancestors.“ Hominids are “the group consisting of all modern and extinct Great Apes (that is, modern humans, chimpanzees, gorillas and orang-utans plus all their immediate ancestors.)”.