Some people are smarter than others. And though animal intelligence is far less well studied, it turns out that within a particular population, say of chimpanzees, some animals are smarter than others, too — and these differences are heritable. To put it another way, some chimps' mothers are smarter than other chimps' mothers.

There are few thornier subjects than human intelligence, and specifically, the idea that it has a genetic basis. If we have been concerned by facing up to the evidence in humans, will we accept it any more easily in our chimp cousins? That's the question posed by biologists who have studied the heritability of intelligence in chimps.

It's an interesting question. While we are relatively happy to accept that traits such as height and eye color come from our parents, it makes us uncomfortable to conclude that the same is true of intelligence. The role of genetics in animal intelligence has been even less fully investigated.