Hamilton's Model

Hamilton's rule is rb - c > 0. Here c is the cost to the giver's fitness (c fewer offspring because of helping), and b is the benefit to the recipient's fitness (offspring gained by the recipient from the help). Here again, "r" is a measure of the relatedness between giver and the receiver [...] Hamilton’s rule says that for unrelated individuals (r = 0) no benefit can overcome the cost of loss of the altruist's fitness (0 - c can't be greater than 0) and aid giving is selected against...

 Evolution of the Whale

Indohyus was not the ancestor of whales, but was almost certainly its cousin. But if we go back four million more years, to fifty-two million years ago, we see what might well be that ancestor. It is a fossil skull from a wolf-sized creature called Pakicetus, which is a bit more whale-like than Indohyus, having simpler teeth and more whale-like ears. Pakicetus still looked nothing like a modern whale, so if you had been around to see it, you wouldn’t have guessed that it or its close relati...