In controlled laboratory experiments another chimpanzee called Judy quickly learns how to use a complex series of manoeuvres, turning wheels and pulling handles in order, to obtain a piece of fruit from a specially constructed wooden slot machine. But even more remarkably other chimps watch her success and then learn the skill themselves.

Learning by imitation is regarded as an essential skill for culture.

Apes display rudimentary traditions which could be interpreted as culture but are they really bright enough to develop a proper culture?

The apes are all stars of a new film - Ape Genius - which gives a fascinating insight into the depth of intelligence of animals who share 99 per cent of human genes. In it they reveal the skills, reasoning powers and emotions that were once thought to be uniquely human.

The stars include Koko a gorilla who understands sign language, Azy an orangutan maths champion, and Kanzi a bonobo who understands more than 3,000 words of English.

The film demonstrates that apes are more like us than we ever imagined and only the lack of a few mental skills has prevented them making the giant evolutionary development steps taken by their human cousins.

What's the little difference that makes the big difference and how big is the gap between Them and Us?, the film asks.

In west Africa Japanese researchers watch a mother care for sick two-years-old infant. She puts her paw on his forehead in exactly the way as a parent would check for a temperature in a child. As the baby chimp's life ebbs away she cares for him devotedly and when he dies she carries him around on her back for weeks almost refusing to accept that he is gone.

It is impossible to know what she is thinking but not difficult to recognise that she is stricken with grief.

"When I see the scene of the mother looking at the baby, I really recognise the emotional life of chimpanzees are so similar to us," says one of the researchers.

But if apes have the power to reason, learn skills, feel emotion and co-operate in a frenzied tree-top hunt for Colobus monkeys as chimpanzees do, why don't we have a planet of the apes?

The film reveals that although apes will co-operate to obtain food they don't have a shared commitment, they don't have the passion to urge or cheer on a tribe member and they do not have control of their emotions. They are also violent, impulsive and display deadly rivalry.

Although they can be taught to recognise symbols and words they don't have the mental capacity to contribute to a 'conversation' - and they don't make small talk. And most important of all although they can imitate, they can't teach or build on the achievements others have made - unlike more successful humans.

Their mental rocket is on the launch pad but it hasn't taken off, the film concludes.

Ape Genius will be shown on the National Geographic Wild Channel on Thursday May 8 at 9.00pm