February 26, 2013

Darwin Days Lecture: “Can Cooperation Evolve by Natural Selection?”

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As part of Darwin Days, a week long celebration of Charles Darwin’s birthday and ideas, Prof. Allen MacNeill ’74, M.A. ’77, biology, gave a lecture titled Can cooperation evolve by natural selection? on Thursday Feb. 14. MacNeill spoke about the theories that have been formulated to explain the seemingly contradictory evolution of cooperation over a casual dinner in Risley Hall.

First, some definitions are in order. According to MacNeill, evolution can be described as changes in the characteristics of a population over time. In the Darwinian viewpoint, there are four criteria that must be met in order for evolution to occur: the traits evolving must vary within a population, the traits must be inherited, the individuals must reproduce to pass on those traits and there must be unequal survival and/or reproduction based on whether or not individuals possess certain traits. Darwin proposed that behaviors, such as cooperation, can evolve by the same rules as physical traits, such as the eyeball or the wing.

MacNeill defined cooperation as “at least two individuals coordinating their activities in such a way that there is a positive benefit for both of them.” A subset of cooperation is altruism, which comes with an extra caveat—in altruistic behavior, the implication is that there is a cost to the altruist and a benefit to the recipient of the altruism.

This begs the question: how can altruistic behavior evolve if altruists are constantly incurring losses to the benefit of selfish individuals who will never reciprocate?

MacNeill outlined just a few of the dozens of theories that swirl around this controversial issue, many of which are rooted in mathematical and statistical arguments.

One theory is kin selection, proposed by evolutionary biologist, W.D. Hamilton.

“What matters in kin selection is not the evolution of the characteristics in the population, but the genes that code for the characteristics,” MacNeill said. This means that individuals will help those who share their genes. According to MacNeill, prairie dogs give a louder alarm call in the face of danger if the individuals around them are closely genetically related.

Kin selection, however, fails to explain interspecies cooperation, which is where reciprocal altruism, more commonly known as tit-for-tat, comes in. Reciprocal altruism is rooted in game theory, a mathematical theory of strategic decision-making that is used broadly in economics, psychology and other fields. The tit-for-tat strategy rules are simple—cooperate first, then reciprocate whatever the other player does. In computer simulations, tit-for-tat is the clear winner against a multitude of other strategies, which provides evidence that cooperation can be beneficial.

A third model that attempts to explain the evolution of altruism is group selection, which has also been described by a mathematical equation. According to MacNeill, group selection argues that evolution occurs on the level of groups as opposed to the level of individuals. If a group that contains altruists is better equipped to survive relative to a group composed of selfish individuals, the group with altruists will win, and altruism will be preserved in that group.

Yet another theory questions the theoretical basis of all the aforementioned proposals; it posits that behavior cannot be inherited by offspring, but is instead entirely learned.

“This theory says that individuals don’t inherit behaviors, but instead inherit the ability to quickly learn behaviors,” MacNeill said.

In light of the slightly overwhelming number of different (and sometimes conflicting) viewpoints, MacNeill concluded by predicting an imminent overhaul of the theory behind the evolution of cooperation and altruism.

“Whenever you have a lot of theories, they’re about to be overturned. Somebody will present a new theory that explains all of them.”

Original Author: Jacqueline Carozza