24 November 2010

Food sharing: Hunter-gatherer "health insurance"

Kim Hill
By pure chance (involving a failed attempt to go hiking and a speeding ticket), I found myself at a talk given by anthropologist Kim Hill, speaking on the "Emergence of Human Uniqueness: Characteristics Underlying Behavioral Modernity."

I previously wrote an article for Scientific American on an Arizona State University workshop that Hill headed up along with Curtis Marean and Lawrence Krauss last February.

Most of Hill's talk was basically the same stuff I wrote about before like that humans are outliers, not unique in any specific way, but contain a combination of non-unique traits that arose through non-unique processes produced a unique outcome -- a "spectacular anomaly."

"If aliens from outerspace came to the Earth," Hill said, then they would be questioning humans instantly because we're so dominant in several ways: technologically, agriculturally, population-wise, etc.

Some would point to the industrial revolution, but Hill argues that hunter-gatherers would have still attracted aliens' attention because they were still the most prosperous species even before agriculture.Humans engage in more ecological niches than all other species combined.

Besides humans, the most successful terrestrial vertebrate is "Canis lupus" (wolves, and that's not counting dog domestication). Both humans and wolves share something in common: cooperative breeding.

So, how do you get this spectacular anomaly?

Hunter-gatherers colonized all the land mass, produced massive megaliths, created complex institutions, and developed languages and cultures.

Hill discusses how he and other scientists came together to discuss what makes humans unique looking at fields of primatology, evolution, hunter-gatherer work, etc.

What makes us uniquely human is a combination of traits that were critical for producing outlier outcomes:

-Cumulative culture

OK, so we know all of this. But now here's the interesting part!

Hill showed data from his work that has to do with the economics of cooperation in humans as compared to chimps. Humans are hypercooperators.

What led to hypercooperation in humans?

Hill discusses that it may be due to:

a) a shift on the feeding niche going from collected foods to extracted foods and predation. This is shown in the paleoanthropolical record from 1) emergence of waist, 2) evidence of cooking, 3) stone tool cut marks.

b) extracted and hunted foods caused by juvenile dependence and long learning period.

Basically, adults need to take care of children for several more years in comparison to chimps. Human kids produce virtually nothing, even as they grow older they produce little versus the adults.

c) high variance in large-package foods promotes food sharing

In other words, Kim says, some adults are hunting and bringing home lots of food, way more than they can eat, or that their nuclear family can eat. This promotes food sharing.

He gives an example of the Ache tribe (hunter-gatherers from Paraguay who he's studied for over 30 years) and how at the end of the day everyone brings their extra food to distribute among the group. Children too are taught to share food from the time they're two years old.

Hill gives data on the percent of food types that are kept versus produced by a nuclear family. Some families give away the majority of food (70 to 90 percent!) they produce (and he joked about comparing that to a tax bracket and socialism).

Food sharing among hunter-gatherers is interesting and complicated, Hill says. The sharing is a type of "health insurance" so that if a man, for example, gets sick or injured taking him out of the production three months, he is covered by the sharing of others. He gives data on "health insurance premiums" given by hunter-gatherers like Ache, Efe, Yora, Tsimane.

Food sharing networks helped us survive and have long lives, Hill said. Because in comparison to chimps, humans have less risk of premature death because if a "chimp falls out of a tree and breaks its arm, it's dead" even though the chimp will heal simply because it will starve to death.

Hill then gave more data on hunter-gatherer habits of women overproducing and then led into cooperative breeding, which is reproducing with the help of others in birth and child rearing.

And, again, wolves are also cooperative breeders, so it's definitely an effective strategy.

"What we now know," says Hill, "is that individuals go through periods of time when they are producing a surplus and other times when families cannot feed all the mouths they have."

To illustrate the point, Hill shows us a picture of a typical hunter-gatherer family that has breeders, helpers, and dependents. He gives data on how these families subsidize food.

"It takes a 'band' to raise a child," is typed up on the slide.

He compares hunter-gatherer systems to an institutionalized social security system. "This is a universal pattern among hunter-gatherer societies," he says. A family without this would not be able to be successful. Kinship like cousins, aunts, and uncles are usually the foundation of human cooperative breeding.

But Hill has been studying how kinship moves to larger social organizations of hunter-gatherer societies.

He showed how chimp communities often are not in contact with each other and often kill each other. But, based on work by Bernard Chapais, pair bonding -- transferring females among groups, for example -- which leads to cooperation between groups.

When a sister is married to a man in another group, a brother will create an alliance with the husband. It leads to sharing food communally.

Hill said people like Paul Davies who are looking for alien species should not be looking for "intelligent life on other planets," but actually be looking for cooperative species -- species that work together to accomplish big tasks.

"Chimps are intelligent and dolphins are intelligent," he said, "but ants are closer to building a spaceship than chimps."

Learn more link: Here's some other crazy neat info from Hill on Amazonian hunter-gatherers widespread belief that they have multiple fathers.

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