If you tickle a young chimp, gorilla or orang-utan, it will hoot, holler and pant in a way that would strongly remind you of human laughter. The sounds are very different. Chimp laughter, for example, is breathier than ours, faster and bereft of vowel sounds (“ha” or “hee”). Listen to a recording and you wouldn’t identify it as laughter – it’s more like a handsaw cutting wood. But in context, the resemblance to human laughter is uncanny.
Apes make these noises during play or when tickled, and they’re accompanied by distinctive open-mouthed “play faces”. Darwin himself noted the laugh-like noises of tickled chimps way back in 1872. Now, over a century later, Marina Davila Ross of the University of Portsmouth has used these noises to explore the evolutionary origins of our own laughter.
Davila Ross tickled youngsters of all of the great apes and recorded the calls they make (listen to MP3s of a tickled chimp, gorilla, bonobo and orang-utan). She used these recordings to build an acoustic family tree, showing the relationships between the calls. Scientists regularly construct such trees to illustrate the relationships between species based on the features of their bodies or the sequences of their genes. But this is the first time that anyone has applied the same technique to an emotional expression.
The tree linked the great apes in exactly the way you would expect based on genes and bodies. To Ross, this clearly shows that even though human laughter sounds uniquely different, it shares a common origin with the vocals of great apes. It didn’t arise out of nowhere, but gradually developed over 10-16 million years of evolution by exaggerating the acoustics of our ancestors. At the very least, we should now be happy to describe the noises made by tickled apes as laughter without accusations of anthropomorphism, and to consider “laughter” as a trait that applies to primates and other animals
Chimps are known to make a variety of tools to aid their quest for food, including fishing sticks to probe for termites, hammers to crack nuts and even spears to impale bushbabies. But a taste for honey has driven one group of chimps in Gabon’s Loango National Park to take tool-making to a new level.
To fulfil their sweet tooth, the chimps need to infiltrate and steal from bee nests, either in trees or underground. To do that, they use a toolkit of up to five different implements: thin perforators to probe for the nests; blunt, heavy pounders to break inside; lever-like enlargers to widen the holes and access the different chambers; collectors with frayed ends to dip into the honey; and swabbers (elongated strips of bark) to scoop it out.
Some of the tools are even fit for the Swiss army, combining multiple functions into the same stick. For example, some were obviously modified at both ends, but one was blunt while the other was frayed, suggesting that they doubled as enlargers and collectors.
These observations were made by Christophe Boesch from the Max Planck Institute for Evolutionary Anthropology and they emphasise yet again the extraordinary brainpower of chimpanzees. It takes an uncommon intellect to be able to design and manufacture a suite of tools and use them in sequence to extract a foodstuff that’s hidden from sight.
Many men think of little else besides sex and meat, but male chimpanzees will sometimes exchange one for the other. Chimps are mostly vegetarian but they will occasionally supplement their diet by hunting other animals, especially monkeys. Males do most of the hunting, but they don’t eat their spoils alone – often, they will share the fresh meat with females, even those who are unrelated to them. Some scientists have suggested that this apparently selfless act is a trade – the males are giving up their nutritious catch in exchange for sex.
Cristina Gomes and Christophe Boesch from the Max Planck Institute for Evolutionary Anthropology have found new evidence to support this idea. They spent four years in the Tai National Park in Cote d’Ivoire watching a group of 49 chimps, including 5 adult males and 14 females. They recorded a huge amount of data on the group’s behaviour, and across 3,000 hours of observation, they were privy to 262 bouts of chimp sex.
These years of voyeurism told them that meat was a big factor in separating the Casanovas from the sexually frustrated males. Females mated more frequently with males who gave them meat at least once, and meat-sharing was much more important than other shows of support such as grooming, sharing other types of food or taking their sides in fights. None of these other actions had much bearing on the male’s sexual success.
Gomes and Boesch wonder if human hunter-gatherers rely on similar trades. That’s certainly been suggested before, especially since better hunters tend to have more wives (or at least, more affairs). These results do nothing to confirm or deny that idea, but they certainly provide strong evidence that chimps, at least, are indeed exchanging meat for sex.
For humans, our culture is a massive part of our identity, from the way we dress, speak and cook, to the social norms that govern how we interact with our peers. Our culture stems from our ability to pick up new behaviours through imitation, and we are so innately good at this that we often take it for granted.
We now know that chimpanzees have a similar ability, and like us, different groups have their own distinct cultures and traditions.
Now, Andrew Whiten from the University of St Andrews has published the first evidence that groups of chimpanzees can pick up new traditions from each other. In an experimental game of Chinese whispers, he seeded new behaviours in one group and saw that they readily spread to others.
In 1997, Swedish inspectors found several stockpiles of missiles hidden in a local zoo. Apparently, the arsenal had been gathered together for the express purpose of being used against civilians. And who was the mastermind behind this collection? A 19-year-old chimpanzee called Santino.
Santino was born in a German zoo in 1978 and transferred to Furuvik Zoo at the age of 5. To this day, he lives in the zoo’s chimpanzee island – a large outdoor enclosure surrounded by a moat. Throughout his residence, he was mostly docile towards the eager visitors, but all of that changed in 1997 when he started chucking disc-shaped stones at them.
Now many of us may have secretly wanted to take part in a spot of tourist-stoning, but Santino’s antics became so common that visitors were actually in real danger. The zoo staff had to take action. One morning, they swept the chimpanzee island and (unlike some other weapons inspectors) they actually found Santino’s arsenal – five separate caches of stones dotted along the shoreline facing the public area. Each one contained 3-8 missiles including concrete slabs, and algae-covered stones that had clearly been taken from the moat.
Mathias Osvath from Lund University, who describes the behaviour in a new paper, believes that it’s clearly premeditated. Until now, it’s been very difficult to work out if natural chimp behaviour involves true forward-planning or represents a reaction to present circumstances. Is a chimp that gathers twigs for termite-fishing planning for the future, or just responding to a more immediate hunger?
There’s no easy answer to that, but Santino’s case is much clearer. One of his caretakers, Ing-Marie Persson has collected plenty of evidence to show that he was deliberately stockpiling weapons of individual destruction for future acts of tourist-stoning.
In the Goualougo Triangle of the Republic of Congo, a chimpanzee is hungry for termites. Its prey lives within fortress-like nests, but the chimp knows how to infiltrate these. It plucks the stem from a nearby arrowroot plant and clips any leaves away with its teeth, leaving behind a trimmed, flexible stick that it uses to “fish” for termites.
Many chimps throughout Africa have learned to build these fishing-sticks. They insert them into termite nests as bait, and pull out any soldier termites that bite onto it. But the Goualougo chimps do something special. They deliberately fray the ends of their fishing sticks by running them through their teeth or pulling away separate fibres – just watch the chimp on the right in the video below.
The result is a stick with a brush-like tip, which is far more effective at gathering termites than the standard model. This population of chimps has modified the typical design of the fishing stick to turn it into a better tool. They truly are intelligent designers.