Do creatures with big brains fare better in the trials of life than those with small ones? Developing a large brain requires an extended childhood, facilitating education. Knowledge is power. ‘Cognitive buffering’, a reserve of know-how and memory, can help an individual deal with the unexpected and get out of tight corners.
Not only does growing a large brain demand extra resources, the costs of running it are high; the human brain, for example, consumes a fifth of the body’s energy. Nor does extra brain-power guarantee survival. At least five brainy hominid species were alive worldwide until comparatively recently, but Homo sapiens is the only one left standing.
The evolution of big brains is puzzling. Few children of our remote ancestors survived to breeding age, so how did the costs and risks of an extended childhood make survival sense in a dangerous world? Would it not have been wiser to reproduce quickly and do so often?
Humans have exceedingly long childhoods but the offspring of other primates, dolphins, and elephants also grow up slowly. Scientists at the Max Planck Institute address this evolutionary conundrum in a paper just published.
They asked themselves two questions; ‘are the effects of extended childhood on cognition specific to humans and other primates or can they be generalised to other species’, and ‘what is the particular role of parenting on the development of cognition in individuals?’
The team looked at baby songbirds, creatures far removed from ourselves on the evolutionary tree. They focused mainly on corvids; the crows and jays. These have the largest brains, in proportion to body size, in the avian world and rival the apes in tool-making and problem-solving.
Young Siberian jays stay with their parents in extended family groups for up to four years. Benefiting from additional food their parents provide, they learn the tricks of the trade by watching adults. Based on a study carried out in Sweden, the Max Planck team conclude that these early experiences increase the youngsters’ success in life; jays tend to live longer and reproduce more efficiently than other songbirds.
The New Caledonian crow is the acknowledged genius of the bird world. It not only constructs and uses tools, it can fashion new ones to suit novel situations it encounters. Remaining with parents for up to three years, a young crow undergoes a valuable apprenticeship. The parents not only tolerate young hangers-on, they indulge them. Juveniles, even ones unrelated to the parents, develop tool-making and food-gathering skills.
Giving young crows a better education is expensive; parents must pay the avian equivalent of school fees, so how do the costs and benefits compare? The behaviour may be demanding, in terms of time and resources, but it pays off; Caledonian crows have evolved the biggest brains of any bird species.
But the researchers draw a more radical conclusion. They claim that an extended childhood period increases the ‘cultural intelligence’ of youngsters. Both corvids and humans, the lead author told Science Daily, ‘have the ability for lifelong learning, a flexible kind of intelligence which allows individuals to adapt to changing environments throughout their lifetime’.
Natalie Uomini et al. Extended parenting and the evolution of cognition. Philosophical Transactions of the Royal Society B. 2020.