The Evolution of Altruism
Darwin's Theory of Natural Selection Applied to Human Kindness
Nov 14, 2009
Although Darwin’s theory of evolution continued to have significant impacts in the field of biology in the days since its conception, its influence on psychology faded as the behaviorist movement came to dominate the field. The core tenets of behaviorism emphasized the nurture end of the ongoing nature vs. nurture debate. Evolutionary principles, standing in support of the nature argument, were pushed to the side during the first half of the twentieth century as psychologist sought to study observable human behavior.
By the 1960s, however, proponents of evolution began to question certain elements of behavior. Primarily, evolutionists were confused by the existence of altruism. That humans and other animals engage in altruistic acts (e.g. risking one’s own life to help another) is paradoxical in light of evolutionary theory. Evolution works though a process of natural selection whereby genetic qualities that prove advantageous to survival and reproduction survive into future generations and qualities that inhibit survival and reproduction do not. Given this process, the tendency to risk one’s life for another should not survive into future generations.
William Hamilton’s Rule of Kin Selection in Understanding Altruism
British biologist William Hamilton found a workable solution to the conundrum. In 1964, he published a concept that has become Hamilton’s rule of kin selection. Essentially, Hamilton wrote that a species would evolve a sense of altruism when its genes predispose individuals to act altruistically toward close relatives.
Therefore, altruistic behavior aids in the propagation of its genes just as in traditional evolutionary theory, but rather than protect its own copies, altruism protects the copies present in close relatives. For example, a predisposition toward altruism might lead an ant to risk its survival or reproductive fitness for the benefit of its sister. Though evolutionists might scoff at the ant’s foolishness and believe that it has effectively acted against the interest of spreading its genes, the truth is in fact the opposite. In helping its sister, the ant has protected its own genes because the sister likely holds copies of them.
Robert Trivers and Reciprocal Altruism
The realization that evolution could be used to explain altruistic behavior led to the resurfacing of evolutionary explanations of other behaviors. In the 1970s, the work of Robert Trivers provided influential insight to the evolution of human behavior.
When Trivers took a job writing and illustrating textbooks for the Educational Development Center in Newton, Massachusetts, he was assigned to work on a textbook about animals. In the course of writing the book, he came across a picture of baboons disciplining their young and realized that it bore a striking resemblance to the way human parents interact with their children. This stroke of insight led Trivers to believe that scientists might better understand the social behavior of humans by observing that of other species.
Knowing nothing of biology or evolution, Trivers became transfixed by the information he began reading. Soon enough, he borrowed enough money to attend Harvard and pursue a doctorate in biology. Before he even attained his PhD, Trivers wrote an influential paper that reexamined Hamilton’s theories of evolved altruism. Although Hamilton’s research concerned primarily non-human subjects, Trivers recognized that a similar phenomenon occurred in humans; however, while Hamilton postulated that individuals will act altruistically only for close genetic relatives, Trivers argued that in the case of humans, individuals are more likely to help people to which they are not related.
An Illustration of Reciprocal Altruism
To illustrate this new perspective on altruism, Trivers used the example of a drowning man. If someone were to witness another person drowning, s/he would risk his/her own life to save the other person even if that person were a complete stranger, Trivers argued in his 1971 article, “The evolution of reciprocal altruism” published in Quarterly Review of Biology.
This flies in the face of the previously held view that altruism exists only to benefit genetically similar animals. So how could Trivers justify his idea? The person would rescue the other, he argued, in the hopes that the other person would someday return the favor.
Benevolent behavior, then, became part of human nature because acts of kindness were reciprocated, which was more beneficial among human predecessors who lived in smaller, stable groups. The concept became known as “reciprocal altruism” and provided a unique perspective on the evolutionary basis of human behavior.
