[tt] [technoliberation] Fairness was an evolutionary advantage for homo sapiens

Wed Oct 10 11:55:13 UTC 2007

----- Forwarded message from "Hughes, James J." <James.Hughes at trincoll.edu> -----

From: "Hughes, James J." <James.Hughes at trincoll.edu>
Date: Wed, 10 Oct 2007 07:41:06 -0400
To: technoliberation at yahoogroups.com
Subject: [technoliberation] Fairness was an evolutionary advantage for homo sapiens
Reply-To: technoliberation at yahoogroups.com

http://www.economist.com/science/displaystory.cfm?story_id=9898270

Patience, fairness and the human condition

Oct 4th 2007

Apes are patient, but only people are fair. That may help explain why
people came out on top

PEOPLE love to catalogue the traits they think characteristic of their
species. Some, such as language, are obvious. Others, such as patience
and a sense of fairness, are more subtle. These traits, however, did not
spring into existence fully formed. They evolved-and to understand human
evolution it would help to know their genetic underpinnings and the
order in which they evolved.

One way of looking at these questions is to compare people with their
closest relatives, great apes such as chimpanzees. Another is to compare
them with each other. Three studies published this week, which take one
or other of these approaches, have cast light on the evolution of both
patience and fairness. It turns out that patience is older than
fairness. It also turns out that although the propensity to be fair
varies a good deal from one person to the next, that variation is rooted
in genetics rather than culture.
The origin of virtues

The essence of patience is the ability to delay the gratification of an
appetite in favour of a greater ultimate reward. Past tests of the
degree to which animals other than people can delay their gratification
have focused on birds and monkeys. Both groups can delay gratification
if a bigger reward is on offer, but only for a few seconds.

Birds, however, are remotely related to humans, and even monkeys are not
as close as apes. In Current Biology, Marc Hauser of Harvard University
and his colleagues compare chimpanzees and humans directly. Both, it
turns out, can be patient to a high degree. In fact chimps are more
patient than people.

The human participants in Dr Hauser's experiment were allowed to choose
a preferred food, such as raisins or chocolate. The chimpanzees were
simply offered grapes-which they usually like. Otherwise the
experimental conditions were identical. The choice was between one unit
of goodies immediately and three after two minutes. Chimpanzees were
nearly four times more likely to wait for the big reward than humans
were. This suggests not only that the trait of patience predates the
split between humans and chimpanzees, some 4m years ago, but that the
trait seems more characteristic of chimps than people.

When it comes to fairness, though, it is a different story. Economic
theory has contrived a species it calls Homo economicus-a "rational
maximiser" who grabs what he can for himself. But, curiously, he makes
no appearance in the ultimatum game, a classic economics experiment.

In this game, two players, a proposer and a responder, divide a reward.
It could be a cake. It could be cash. It could even be a bunch of
grapes. The game is so named because the proposition is an ultimatum.
The responder can either accept the division or reject it. If he rejects
it, both players receive nothing.

Homo economicus would accept any division in which his share was not
zero. But that is not what happens. Scores of studies have run the
ultimatum game across cultures and ages. Universally, people reject any
share lower than 20%-apparently to punish the greed of the proposer.
People do not act like Homo economicus. Instead, they are the arbiters
of fairness.

To find out if chimpanzees share this sense of fairness, Keith Jensen
and his colleagues at the Max Planck Institute for Evolutionary
Anthropology, in Leipzig, designed a way for chimps to play the
ultimatum game. Their version started with a pair of trays far from the
players' cages. Each tray had ten raisins divided in different ways
between two pots-say eight and two, or five and five. One chimp was
allotted the role of proposer. He could choose one of the trays, pulling
it by way of a rope just halfway to the cage. The other, the responder,
could then choose to pull on a rod, bringing the tray close enough for
both to get the raisins, one pot for each. If the responder chose not to
pull the tray closer within a minute, the offer was considered rejected,
and the game concluded.

The result, which Dr Jensen reports in Science, is that chimps are
simply rational maximisers-Pan economicus, if you like. Though proposers
consistently chose the highest possible number of raisins for
themselves, responders rarely rejected even the stingiest offers.

This is a telling outcome. A number of researchers in the field of human
evolution think that a sense of fairness-and a willingness to punish the
unfair even at some cost to oneself-is humanity's "killer app". It is
what allows large social groups to form. Without it, free-riders would
ruin such groups, because playing fair would cease to have any value. Dr
Jensen's previous experiments have shown that chimpanzees are willing to
punish actual thieves. But his new data add weight to the theory that
the more sophisticated idea of fair shares, which underpins
collaborative behaviour, appeared in the hominid line only after the
ancestors of the two species split from one another.

Nor, according to the third of this convenient trilogy of papers, is a
sense of fairness rooted in culture. Rather, it is genetic-as it would
have to be in order to evolve. Paradoxically, discovering this relies on
the fact that not everyone possesses it to the same degree.

As they write in the Proceedings of the National Academy of Sciences,
Bjorn Wallace of the Stockholm School of Economics and his colleagues
have shown this by playing the ultimatum game with twins. They used the
classic trick of neutralising the effect of upbringing and exposing that
of genetics by comparing identical twins (who share all their genes)
with fraternal twins (who share half).

Each twin of a pair played the ultimatum game, both as proposer and as
responder. Dr Wallace found, in the case of identical twins, a striking
correlation between the average division that each member of a pair
proposed and also between what they were willing to accept. In other
words, their senses of what was fair were similar. No such correlations
were seen in the behaviour of fraternal twins.

Besides showing that a sense of fairness has a genetic basis, this
result also raises a question: why should the sense of what is fair be
so variable? It may be that in a population of the fair, the unfair
prosper while amongst the unfair, the fair are better off. The result
would be an equilibrium in which various attitudes to fairness do just
as well as each other. But why, exactly, that should be the case is a
subject for another day's research project.

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