A gazelle on the African savanna is trying not to be eaten by cheetahs, but it is also trying to outrun other gazelles when a cheetah attacks. What matters to the gazelle is being faster than other gazelles, not being faster than cheetahs. (There is an old story of a philosopher who runs when a bear charges him and his friend. "It's no good, you'll never outrun a bear, " says the logical friend. "I don't have to," replies the philosopher. "I only have to outrun you.")
In the same way, psychologists sometimes wonder why people are endowed with the ability to learn the part of Hamlet or understand calculus when neither skill was of much use to mankind in the primitive conditions where his intellect was shaped. Einstein would probably have been as hopeless as anybody in working out how to catch a woolly rhinoceros. Nicholas Humphrey, a Cambridge psychologist, was the first to see clearly the solution to this puzzle. We use our intellects not to solve practical problems but to outwit each other. Deceiving people, detecting deceit, understanding people's motives, manipulating people—these are what the intellect is used for. So what matters is not how clever and crafty you are but how much more clever and craftier you are than other people. The value of intellect is infinite. Selection within the species is always going to be more important than selection between the species.
Mankind has always been his own worst enemy, ready to sell his own mother for a little bit of power or money or territory. But at the same time being back-stabbing apes is what gave us our intellect in the first place. Discord makes the world go round. Strife is how we hone our skills and settle dispute. People that aren't alert enough or smart enough to out-maneuver his fellow man get dispensed with rather quickly. Any illusion of altruism is purely coincidental. Sure, social animals like ants are really amazing but when is the last time they sent a rocket to the moon?