Humans, as a species, have a fairly long juvenile period. ‘There must be some evolutionary advantage to that’, explains biologist Jorin Veen. ‘There is this theory: embodied capital, which says that this longer juvenile period is linked to our diverse diet, which in turn is linked to our larger brains. We’re able to consume more types of food, and as a result, we can have bigger brains, because those require a lot of energy - even in periods of scarcity. However, in order to learn how to gather that food, we need a longer juvenile period. Those traits are thought to have evolved in tandem.’

Together with Professor by special appointment Cognitive Behavioural Ecology and primatologist Karline Janmaat, Veen conducted research on hunter-gatherers. ‘Great apes like chimpanzees mainly eat fruits and leaves’, she says. ‘But humans are unique in that they also gather underground tubers, fish and eat more meat. Because much of that food is shared among the group, it’s beneficial to specialise yourself. For example, one person might be able to dig up tubers very efficiently, while another has the strength to climb the tallest trees. On the whole, this provides the group with more food and energy - even during periods when fruit is scarce.’

To test how that knowledge is acquired, Veen, Janmaat and their colleagues travelled to the Republic of Congo to observe the BaYaka, one of the last peoples in the world still living predominantly as hunter-gatherers.

BULLIED OR ABANDONED

‘We actually wanted to make a direct comparison to see how our close relatives compare to humans, who grew up in the same environment’, says Janmaat, who has previously researched chimpanzees. ‘That’s how we found the BaYaka people. And when we got there, we discovered that their children already start gathering food in the forest from the age of six.’

For Veen, this meant long days of wandering through the jungle. He kept track of how much time every child spent on gathering different types of food and when they returned to camp, he checked which foods each of them ate.

‘You’d often rise with the sun. Every day was different. Sometimes you’d spend the day digging up tubers, and sometimes your day consisted entirely of fishing. The children liked it when I tagged along. They often asked me “When will you come along with me?”. But we tried to influence their day as little as possible. So we didn’t send them in a particular direction by asking if they were going to a specific place.’

He observed that the children had specialised tasks from a fairly young age. Boys seemed more focused on collecting fruits, seeds and honey high up in the trees, while the girls were more likely to forage for tubers and fish.

But something remarkable happened when it was time to eat. ‘Almost all the food was divided equally. The boys’ and girls’ diets were practically identical. Even those who didn’t go out to forage themselves were given food.’

‘There’s no choice but to work together’, Janmaat adds. ‘It’s impossible to survive on your own in such a forest. Their social system ensures equality. If you don’t share something fairly, you will be bullied or abandoned.’

Veen: ‘If you have two of something, and someone asks you “beke me” - “Give it to me” - you simply have to do so. You have to share, regardless of whether it’s a young person, an older person or a stranger. If someone says “no”, it’s perceived as very rude.’

The data collected by the researchers over the course of a year showed that food patterns varied considerably. ‘In the dry season, the BaYaka collect a lot of tubers, whereas in the rainy season, they collect more ripe fruits’, explains Veen. ‘And there is one short period in which they eat caterpillars.’ The scientists wanted to know how the children remembered where to find those. ‘If you can only collect those caterpillars for a single month, you have to remember where the right trees are for a whole year. And that’s a very long time when you’re seven years old.’

A THOUSAND DIFFERENT PLANTS

In order to test whether the children only remembered the right place, or actually recognised plant species, the researchers showed them pictures and leaves of trees. Then they asked which fruits belonged to them. ‘I expected that it would be too difficult,’ says Veen. ‘But I was genuinely surprised by how well they were able to do that from a very young age.’

The results are particularly interesting for Janmaat, who has been studying foraging behaviour in chimpanzees for some time. ‘You can’t show pictures to wild chimpanzees. We used to observe which trees they inspected. Their behaviour showed that they would suddenly stop and stare up at the top of a tree, especially in species where they were likely to find fruit. I’ve always wondered if they could remember all those individual trees or the spatial location or if they actually had botanical knowledge. Recognising plant species is not easy in a rainforest with a thousand different plants. That’s why I was so excited to see that these children are truly able to recognise the species. It gives me some sense of understanding, even though I can’t say for sure whether the chimpanzees also truly possess knowledge of species.’

EMPTY FOREST

Although Veen and Janmaat are one step closer to unravelling human evolution, chances of conducting further studies on this type of hunter-gatherer groups are diminishing rapidly. The BaYaka and other groups around the world are eating increasingly less foraged food and increasingly more food of agricultural origin. Thus, their unique culture and knowledge of nature is in danger of disappearing. Janmaat and Veen see their research as one of the last remaining chances to understand the emergence of embodied capital.

‘The future looks bleak’, says Janmaat. As long as there is forest, I expect they will keep searching for answers, but the jungle is becoming emptier and emptier because of hunting and logging. And hunter-gatherers are not allowed into national parks.’

Veen: ‘I think a lot of the knowledge we’ve seen with the BaYaka people will be lost because they will have to start living more and more in villages instead of in the forest.’

Janmaat: ‘I hope that nature and culture conservationists will join forces in the future, so that not only the rainforest but also the knowledge about our evolutionary history will be protected.’