Leiden University: Foraging skills may have made the essential difference in the evolution of huge brain
Hunter-gatherers acquire their food through complex gender-specific foraging techniques for a relatively stable and diverse supply of energy. New research indicates that this specialisation by boys and girls starts at a very young age. Most likely, this enabled the human species to evolve much larger brains than other primates, concluded a team of Leiden and Amsterdam researchers. Publication in the journal Frontiers in Ecology and Evolution.
Humans have brains three times the size of that of other primate species. A diverse, high-quality diet and a prolonged childhood with sufficient time to learn complex food acquisition skills are thought to be important evolutionary drivers of our large brains. In contrast to the diet of other primates, the human diet is characterised by a diverse variety of high-quality and difficult-to-acquire foods, such as meat and fish as well as underground tubers or many species of nuts and caterpillars. To collect these, complex foraging skills are needed that are thought to be developed from an early age.
798 hours of observation
Biologist Jorin Veen is first author and conducted the work for his MSc study at the University of Amsterdam (UvA). He was supervised by Karline Janmaat who is a cognitive behavioural ecologist en connected to Leiden University (Cognitive Psychology) and the UvA. She investigates how humans and other primates forage – search for and acquire food. To better understand how humans learn their foraging skills, the international research team accompanied 27 children of a modern forager society, the BaYaka, in the Republic of the Congo for one year. Their children start foraging independently in peer groups from as young as five years old. The researchers investigated the children’s foraging methods, dietary composition, and botanical knowledge on their daily food-finding trips. Besides observing the behaviour, they also conducted nutritional analyses of the collected food. The fieldwork resulted in a unique dataset containing 798 hours of observational data.
Entering the rain forest without parents
The BaYaka children spent one-third of their time searching and acquiring food. Half of that time, they searched independently from adults and showed a high level of autonomy. ‘I was impressed to see how skilled the children were already at a very young age,’ says Jorin Veen, first author of the paper. ‘The largest share of the food were fallen fruits, seeds, and tubers, but the children also climbed 40 meters high trees to collect honey or fruits, which can be a risky endeavour.’
Differences between boys and girls
The results revealed an early onset in the specialisation in foraging skills. Foraging groups with more boys were more likely to eat fruits and seeds, which often requires risky climbing skills, while girls were more likely to collect tubers. ‘Acquiring food is not child’s play. Collecting tubers requires exceptional identification and digging skills, as the liana that leads to underground tubers are not easy to recognize and keep track off’, explains Professor Karline Janmaat, special chair in Cognitive Behavioural Ecology in Leiden and ARTIS. ‘This early onset of a gendered-based specialisation of foraging skills, combined with the high level of food sharing in hunter-gatherer societies, likely enabled the human species to have a more stable energy and nutrient supply – a supply that could have ultimately enabled us to afford a substantially larger brain than our closest living relatives’, Janmaat says.
‘Our analyses revealed, that especially the fruits, which made up 40 per cent of the children’s diet, contained more sugars, especially glucose and fructose, compared to other plant items’, says co-author Professor Nicole van Dam. ‘No wonder, that they put so much effort into obtaining them.’ Van Dam, who led the molecular analyses, headed the Molecular Interaction Ecology group at iDiv.
Interdisciplinary collaboration
The research is the result of an interdisciplinary collaboration between a botanist and cognitive behavioural ecologists from the University of Leiden and Amsterdam, chemical ecologists from iDiv, anthropologists from MPI-EVAN in Leipzig and nutritional ecologist from the Charles Perkins Centre from the University of Sydney.
Banner: BaYaka boy using self-made climbing gear to climb a tall Pancovia laurentii tree without low hanging branches (Picture by Karline Janmaat with permission of boy and caretakers)