The fact that all our ape cousins - chimpanzees, gorillas and orangutans - can acquire signs - is powerful evidence that our hominid ancestors' first language was gestural and that the vocal version of language was a relatively recent development. My own guess is that vocal language began emerging about 200,000 years ago.

The chimps love holidays - in fact Tatu actually anticipates them and asks about them.

Growing up on a farm taught me a reverence for all forms of life. We were a large and poor farm family, so that meant that we had to kill and eat our animal friends. When you do that you are aware of the sacrifice that someone is making so that you may live. My mother always made sure we were thankful for those precious gifts.

The fact that all our ape cousins - chimpanzees, gorillas and orangutans - can acquire signs - is powerful evidence that our hominid ancestors' first language was gestural and that the vocal version of language was a relatively recent development. My own guess is that vocal language began emerging about 200,000 years ago.

With regard to the alternatives, we already have them. The cellular and genetic lines of research in humans are the most promising. AIDS is caused by a virus, so it makes sense to study the virus, not chimpanzees. We have learned virtually nothing about AIDS from the chimpanzee. Every major advance in AIDS research ... has come from human studies.

With every passing year we discover more evidence to support Darwin's revolutionary hypothesis that the cognitive and emotional lives of animals differ only by degree, from the fishes to the birds to the monkeys to humans.