Building a world of
resilient communities.



Human brain "paid off" by long life

A theory portraying children as start-up companies and middle-aged adults as their investors has been proposed to explain why humans have such big brains and long life spans.

Evolutionary biologists have puzzled for decades over why humans live twice as long as chimpanzees and gorillas and have brains three to four times larger than their closest living relatives.

"We're thinking of the brain as an investment," says economist Arthur Robson, at the University of Western Ontario. Robson and anthropologist Hillard Kaplan, at the University of New Mexico, believe this investment is so substantial that it requires a longer human life span to give it the time to pay off.

"The combination of issues that they raise is novel - a useful first step," says evolutionary biologist Michael Rose, at the University of California at Irvine. But he warns against putting too much confidence in a mathematical model: "If you're a good applied mathematician, you can come up with a model to give you any conclusion you want."

Nonetheless, Rose is intrigued by the explanation of why human children are so unproductive for so long. "This is the best paper on the evolution of teenagers I've ever read," he says.

Enormous debt

The inspiration for Robson and Kaplan's theory came from the observation that children in modern day hunter-gatherer societies consume more calories than they produce, accumulating an enormous debt that peaks at age 20.

As active young adults, they produce more than they consume, but it takes decades to pay off their childhood debt. Only at age 50 do they start moving out of the red and into the black. They then begin to make a net contribution of resources to their society, offsetting the debt of the children in the next generation.

The researchers noticed the parallels between the energy flows in these societies and cash flows in start-up companies, and applied an economic model to human evolution. They treated physical and mental capacities as "embodied capital", with the brain representing a special form of capital that increases in value over time.

Predator protection

According to the model, the brain requires such an enormous investment of energy during childhood that human ancestors must have evolved long life spans to make that initial investment worthwhile.

Robson and Kaplan believe these early humans must have lived in an environment where food gathering was complicated, favouring the development of big brains. They also suspect that the environment reduced the risk of premature death by affording some protection from predators.

The model therefore assumes that the environment was the key factor shaping human evolution. But, Rose argues, this leaves out the sophisticated social interactions that must have also contributed to development.

Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.152502899)

What do you think? Leave a comment below.

Sign up for regular Resilience bulletins direct to your email.

Take action!  

Find out more about Community Resilience. See our COMMUNITIES page
Start your own projects. See our RESOURCES page.
Help build resilience. DONATE NOW.


This is a community site and the discussion is moderated. The rules in brief: no personal abuse and no climate denial. Complete Guidelines.



As I step out on the porch before sunrise Thanksgiving morning, the air will …

The Shadows of the Cave

Some of us prefer sun and wind and depth and color to the play of shadows on …

Zarzalejo Futuro: future scenarios

What does it look like when Transition meets the 15M movement in the context …

Becoming Pattern Literate

The word “pattern” takes us over a vast territory.

Resilience Reflections with John Thackara

It’s taken me a long time to learn respect for the ways millions of …

A Review of Books 2 and 3 in the After Oil Science Fiction Anthology Series

This year saw the publication of not one, but two, more worthy additions to …

Sending Them a Message

If we want to “send a message to those who hate us,” here’s a new one: Come …