There are many ways that our great ape relatives can remind us of ourselves: through their anatomy, cleverness and social relationships, for instance. But never has the resemblance been so striking for me as today, when I watch gorillas carrying out a very human past-time: solving puzzles.
The gorillas in question live at  in Kent in the UK. The task involves moving a hazelnut treat down a vertical maze using sticks or the inbuilt cogs, until it is released at the bottom. It is very similar to a game I loved as a child, called , still played today.
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The task is part of a research project by at Birkbeck, University of London. I have tagged along, ostensibly to learn about her work, but my real goal was seeing the gorillas. Never before have I had such a good look at these animals, as some of them cannot resist coming to the front of their enclosure to work doggedly away at the mazes.
Tibs, a skilful older female, carefully selects sticks, breaks bits off to shorten them and nibbles off leaves. She determinedly moves the nuts around the course, clutching a bar for support with big leathery fingers that have surprisingly human-like fingernails. Her expression seems to reflect intense attention, like a person doing a jigsaw puzzle.
The research is investigating an idea about the origins of language. Linguists debate whether the first languages were based on hand gestures rather than grunts. But Forrester’s team are investigating an even earlier stage in the process – the mental abilities that language built on. “There would have been stuff going on in our ancestors’ brains that we have extended for language,” says Forrester. “We’re trying to learn what kind of behaviours it was supporting previously.”
One possibility, , is tool use, which has several features in common with language. They both involve sequences of precise physical movements – whether of the hands or the mouth and vocal cords. They also require breaking down a complex final goal into simpler intermediate ones and achieving those in the right order. “If you don’t put your words in the correct order the meaning will be obscured,” says Forrester.
Support comes from the fact that the part of the brain that supports language in people, an area usually on the left side of the brain that is expanded compared with the right, is in people and in apes and monkeys. And that left-sided expansion is also . “As they do not possess human language, this suggests the neural mechanism is older than language,” says Forrester.
The puzzle boxes are designed to have similarities with the cognitive demands of language, requiring ordered sequences of physical movements. “We have simple cogs that are equivalent to words, and we have double cogs, which could be analogous to how verbs or adjectives act on a noun,” says Forrester.
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Her team wants to know at what age the ability to do the puzzle boxes emerges in gorillas, chimpanzees, orangutans and human children, and to see if the younger individuals learn by copying adults, another shared feature of both tool use and language. The work could also shed light on why some human children have difficulties learning to talk, says Forrester.
As I watch, a two-year-old gorilla called Vuko scurries over and observes an older female at work. Later, Vuko wiggles a finger in one of the holes experimentally but cannot yet figure out the mechanism. I know we shouldn’t anthropomorphise but I can’t help seeing disappointment in her big brown eyes.  “Language looks super-unique on the surface, but the brain processing that’s going on underneath it can’t be unique,” says Forrester. “If we can understand that, it helps us understand how humans came to be.”
