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ResearchBlogging.orgFood sharing is an important human behaviour that enables our modern, complex society to function as it does. Since food is distributed throughout the group everyone does not have to spend their time farming or hunting.

This frees up their time to do other things, like become specialist tool makers or write entertaining blogs on human evolution. With each person able to become experts in a different field the society as a whole will begin to improve.

Such a “division of labour”  means someone could become an excellent blacksmith, able to provide everyone with tools far superior than those which they could’ve made in their spare time between hunts.

However, whilst food sharing is a useful behaviour it is also open to exploitation. If you work hard and help obtain food for others they could also work hard to make you a shiny new spear with which to do so. Or they could not, leaving you out of pocket.

University of Liverpool

Which is why society views all University students with suspicion

Most groups have mechanisms with which to ensure food sharing continues, despite its potential to be exploited. Western culture, for example, trades money for food to ensure the farmer is getting the benefits of giving the food he makes to others.

Many hunter-gatherer groups use a similar system to ensure a hunter enjoys the advantages of food sharing, although they normally aren’t as instant as our money system. “You let me have a bite of your antelope now and I’ll give you the next bird I kill.”

Others simply use social pressure to ensure everyone shares any food they get. Worried you’ll be left worse off and don’t want to give food to people who might not return the favour? Well tough, they’ll throw you out the group and I doubt you’ll do too well on your own.

However, this is starting to sound a little bit like…dare I say it….irreducible complexity. If a system to counteract exploitation is required for food sharing, yet that system is contingent upon food sharing which came first?

One of the currently favour explanations for how food sharing got started is “tolerated theft.” People like this because it posits nothing more than animals trying to behave efficiently, which they do. No money, social pressure or anything “irreducible” is needed.

The idea behind tolerated theft is that the more of a resource someone has, the less useful each unit is to them. If I kill a gazelle I won’t be able to eat it all by myself so I have little motivation to defend the entire kill from other people, so I allow them to take it.

After all, it’s not a good use of my time and effort to stop someone eating a leg I wouldn’t be able to eat anyway. So by virtue of my laziness (and believe me I am lazy) I have “invented” food sharing.

Now, say tolerated theft meant someone had let me steal a bit of their kill yesterday. If they stumble across my kill today I might be more tolerant of them today. Perhaps I’d let them take a bit more of my kill than usual since they’ve proven themselves a worthy ally.

Thus my laziness (and willingness to try and get a free meal from others) has not only lain the foundation of food sharing, but reciprocity too. Money began with me!

Now if you’re starting to think this whole hypothetical tale is starting to sound a bit far fetched (okay, I’ll admit I didn’t invent money), remember that tolerated theft has been observed in several other animals.

Even our evil cousins, Pan troglodytes, will allow other members of the group (even if they aren’t their family) to take their food if they have too much food. Crucially, they also seem to be more tolerant of individuals who have allowed them to steal food in the past. In other words they are reciprocal.

But our understanding of the origin of food sharing is not yet complete. We might now how it started and how reciprocity got going, but what about social pressure? After all, some modern hunter-gatherer groups are driven to share by the culture they live in. How did that start?

Scientists studying capuchins may well have the answer. No surprise really, capuchins are the most awesome of all the monkeys.

The experiment in question consisted of placing two capuchins in adjacent cages (for the purposes of this, we’ll call them A and B, although in the experiment they actually had names).

When one capuchin (A) was given food they could either eat it near the other cage, where the other monkey (B) could reach through and steal some food or A could take it to another part of their enclosure where their neighbour could not steal food.

Before giving A food, they sometimes also gave B some capuchin chow (maybe a capuchin-o). They found that when B hadn’t been fed the other capuchin was more likely to allow them to steal some of their food.

This effect was not the result of wanting to give food to your family (since the two capuchins were unrelated) and wasn’t due to B simply choosing not to steal some of A’s food when he had been fed. They also gave B some food but made sure A couldn’t see and found that A would still let B steal some of their food.

What I just said in graph format!

So basically, if capuchin A thought capuchin B was hungry they let them have some food. This may well form the basis for the social pressure that makes many modern hunter-gatherers share food amongst the community. “Society tells me to share food because if I don’t you will go hungry” could stem from “that monkey is hungry, I’ll let him have some of my food.”

As well as deepening our understanding of how food sharing started, this research also raises up some far reaching implications for other behaviours. Could this sharing with other monkeys also form the basis of altruism? Are capuchins empathetic?

If so then not only does this research provide clues on the origin of food sharing but may well be the beginning of morality as well. Of course, that’s a very big claim and a big quantity of research will be needed to back it up. Whilst this study was rigorous, it was only done on one group of one species.

But still, this work is at the very least a good addition to our understanding of food sharing origins, but could contain some information regarding the evolution of morality. I’m excited.

Yuko Hattori, Kristin Leimgruber c, Kazuo Fujita, Frans B.M. deWaal (2012). Food-related tolerance in capuchin monkeys (Cebus apella) varies with knowledge of the partner’s previous food-consumption Behaviour, 149 (2), 171-185 : 10.1163/156853912X634124

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Jim Thomerson · 20th April 2012 at 1:31 am

I’ve read that vampire bats who have had a good blood meal will share with individuals not so fortunate,

    Adam Benton · 20th April 2012 at 1:40 am

    Interestingly, they’ll only share with others that have also shared blood in the past. The bats are also reciprocal in nature. Indeed, if you introduce a new bat into the colony (or whatever it is you call a gaggle of bats) then other bats will refuse to feed it since they don’t know if the new individual can be trusted to repay their debts.

    Its fascinating stuff and I was planning on mentioning it, but at >1000 words I felt the blog was long enough without additional examples of “altruism.” Needless to say, there are many more.

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