Illegal logging and mining, and legal deforestation, are destroying their habitat over enormous areas; the so-called “bushmeat” trade is decimating their numbers directly. Scientists have no doubt that they are heading directly for extinction and, within one or perhaps two generations, they may be gone in the wild.Yet most of the 23 countries which hold great ape populations are among the poorest in the world, and for them, wildlife protection is sometimes an unaffordable luxury. All of these reasons apply to the four species of great apes, the gorilla, the chimpanzee and the bonobo or pygmy chimpanzee from Africa, and their Asian counterpart, the orangutan; but it is surely their closeness to us in so many ways – we come from a common ancestor and share more than 98 per cent of our DNA with them – that makes the case for preserving them special, even overwhelming. “The great apes,” said the UN treaty signed to protect them at the weekend, after much effort by conservationists, “form a unique bridge linking humans to the natural world.”

Many reasons can be put forward for preserving different parts of the earth’s wildlife.

In a rich and complex social life, they clearly experience a range of emotions, including joy and grief. Even more strikingly, they show the beginnings of morality, in the way that excessive harassment of a subordinate by a dominant animal will evoke expression of unease by other group members. There are economic reasons (human communities can benefit directly), ecological reasons (other ecosystems are dependent on particular animals or plants), even aesthetic reasons (the world would be a poorer place without nightingales and primroses). They are far closer to us than many people realise.

They make and use tools; they employ plants for self-medication. My wife and I stayed with him two years ago, and his main topic of conversation was the future of the village colleges in the area. But perhaps my abiding memory will be of a dinner at his daughter Liz’s house in my constituency in West Lothian where he displayed his overwhelming driving force, curiosity. On that occasion, it was curiosity about the Scots; usually it was curiosity about anything in the universe, and particularly the universe itself.Tam Dalyell. Indeed, he was the best man in Whitehall at dealing with Zuckerman.Even when he faced the difficulties associated with Parkinson’s disease, Hermann and Christine Bondi opened the hospitality of their home in Cambridge. In a charming way, he would say either “That is cant” – a favourite word – or “You are justified in holding that opinion.”When I got into huge trouble over the visit of the Select Committee of the House of Commons to Porton Down and was had up at the Bar of the House of Commons, with the Speaker putting his black cap on, Bondi took it on himself, with his friend, Solly Zuckerman, the government chief scientist, to intercede on my behalf.