MINE IS A sort of upmarket Estuary English (think Essex girl in a Docklands penthouse). Unless I am enraged, in which case the aitches are inelegantly jettisoned.

Did you know that monkeys have accents too? Scientists have found that groups of Japanese macaque monkeys “speak” differently, and those differences depend on where they live. The monkeys make “coo calls” to keep in contact with each other, and these calls vary in pitch.

Nobuo Masataka, professor of animal behaviour at Kyoto University, studied two troops that are separated from each other by 700 kilometres (435 miles). One group lives in a forest on a southern Japanese island, the other on a mountain in central Japan. Over a period of eight years Professor Masataka recorded the feeding calls issued by the female monkeys in both troops. Those made by the island dwellers were, on average, 110Hz higher than those made by the mainland troop.

“One of the characteristics of human language lies in its modifiability,” Masataka told National Geographic. “Japanese monkey vocalisations share this characteristic with our language.” He suggests that higher frequencies carry better in a forest.

So, accents are not unique to humans. One person who will be unsurprised is the primatologist Frans de Waal. The 57-year-old Dutchman has spent the best part of 40 years studying the great apes, in particular the chimpanzee and the bonobo (also called the pygmy chimpanzee), which are our closest relatives. I had the privilege of meeting him in November, when he came to Britain to talk about his book Our Inner Ape.

His observations have chipped away at the barrier that supposedly separates human beings from our inferiors on the evolutionary tree. One by one, traits thought to be fundamentally human — language, tool use, altruism, culture — have been discovered in chimps and bonobos. Chimps can count, learn sign language and can even be taught a computer language. Chimps can tutor each other in unfamiliar ideas — a phenomenon that was, until recently, thought to be uniquely human.

Each finding reduces another pillar of human superiority to dust and brings us closer — sometimes unnervingly so — to our hairy jungle cousins. Professor de Waal clearly regards the dismantling with approval but complains that those who feel threatened by the narrowing gap keep moving the scientific goalposts.

“The classic example is language,” Professor de Waal told me. “The linguists used to say that language is defined as symbolic communication. People were happy with that until apes were shown to have symbolic communication. So the linguists said, ‘Actually, the most unique feature of language is syntax’. That’s what I mean by moving goalposts — we can never satisfy them.

“We recently demonstrated that chimps learn from each other — cultural transmission, in other words — and as soon as that happened there were critics redefining imitation and copying, right in front of us. It’s started to amuse me because it’s so predictable.”

One of the most intriguing ideas Professor de Waal and I discussed was whether human beings are more closely related, in evolutionary terms, to the murderous chimpanzee or the peace-loving, sex-obsessed bonobo. The chimp is commonly regarded as our closest relative, which has led to our own species being depicted as the Killer Ape. Recently, however, scientists discovered that chimps lack the gene for producing vasopressin, a hormone that promotes social bonding, which is present in both humans and bonobos.

If humans do turn out to be genetically closer to the bonobo, Professor de Waal said, “it will overturn everything we’ve been saying for the past 40 years. During this time people have lived with this coherent picture that humans are aggressive, chimps are aggressive, and so our common ancestor must have been aggressive and that aggression is therefore part of human nature. But if you look at human history, there’s no strong evidence for warfare that goes back further than 15,000 years.”

Bear in mind that bonobos know no inhibitions — they like sex any which way, with whoever is close by. While humans shake hands as a social greeting, Professor de Waal points out, “bonobos offer genital handshakes”. Lusty Ape sounds so much more appealing than Killer Ape, don’t you think?

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