Scientists have long sought explanations for human behaviors and motivations, propelling some to the forefront of their discipline. They have changed the face of modern thought, contributing their ideas as a foundation for further hypothesis and investigation. One such individual is William Hamilton, whose theories concerning the genetic basis of behavior expanded the Darwinian view of natural selection beyond its original scope.
Although William Donald Hamilton was born in Cairo, Egypt in 1936, he was a British citizen. He attended Cambridge University as an undergraduate and received a Bachelor of Arts degree in 1960. Following this, he began earning his doctorate at the University of London in genetics, which he completed in 1968. This was a busy time for Hamilton. At this point in his life, he began his teaching career as a lecturer of genetics at the Imperial College of Science and Technology, where he remained until 1977. More important, he developed his ground-breaking theory of kin selection, which was published in 1964. In addition, he was married in 1967 (American Men and Women of Science, 1986).
In 1977, Hamilton decided to leave England for the United States to accept a professorship at the University of Michigan, Ann Arbor. Here, he was part of the evolutionary biology faculty in the division of biological sciences. This allowed him to pursue his interests in kin selection and the evolution of social behavior. Hamilton remained in Ann Arbor until 1984, when he returned home to England. He accepted an offer from the University of Oxford as a Royal Society Research Professor, where he remains today. At Oxford, his career has flourished as he has explored a variety of phenomena, including population genetics, sex ratio, the evolution of insects, and sexual reproduction. He is currently in the Animal Behavior division of the department of Zoology (American Men and Women of Science, 1986).
In addition to his various publications, Hamilton has earned several honors and been granted membership to a variety of organizations. In 1975, he was the recipient of the Science Medal from the Zoological Society of London. Later, he was awarded the Newcomb Cleveland Prize by the American Association for the Advancement of Science (1981). More recently, in 1993, he was given the Crafoord Prize. He is a member of the British Genetical Society, the American Society of Naturalists, and is a foreign honorary member of the American Academy of Arts and Sciences (American Men and Women of Science, 1986).
William Hamilton has expanded the ideas of evolution and natural selection to account for apparent conflicts with explanations posed for altruism. He is still making significant contributions, continuing to propose new ideas and tweak old paradigms.
The concept of Darwinian evolution has shaped scientific thought since its 1859 introduction in On the Origin of Species. The theories of natural selection and individual fitness have provoked us to view all species in an entirely new light. Yet, certain questions have arisen concerning the behaviors that lie apparently beyond the scope of evolution. For instance, one of the greatest contentions has been in reference to the extensive occurrences of altruism in nature.
To explain altruism, Hamilton sought the most evident example that he could find: bees. These animals exist in a stringent social hierarchy. The workers are sterile, serving only to protect and fulfill the needs of their queen, rather than reproduce themselves. Superficially, this seems in direct opposition to Darwinian evolution, in that the individual is unable to contribute to the gene pool to augment his or her fitness (Barash, 1977).
When explored further, however, the deferment of reproduction in social insects is quite logical. This was the focus of Hamilton’s theories of kin selection and inclusive fitness. Hymenopteran insects, such as bees, wasps, and ants, possess a unique reproductive strategy known as haplodiploidy. In this system, the insects have more genes in common with their sister, the queen, than with their own offspring (had they any). Thus, the persistence of the genes is superior to that of the individual. This is the underlying principle which Hamilton explored in formulating his theories (Barash 1977).
Hamilton argues that an individual can oversee progress of his genes in two ways. First, the most obvious way is proximally through its offspring. This was the foundation of Darwinian evolution. However, Hamilton discovered that an additional means of genetic influence existed in the rearing of a relative’s offspring. In this incidence, many of the genes lie in common with the altruistic individual, thus propagating his genotype indirectly (Crawford, 1987). Specifically, Hamilton termed this as kin selection. This was the phenomenon found in the altruistic behaviors of the bees. In the evolutionary perspective, kin selection actually refers to the "selective pressures favoring such help" (Noonan, 1987). By doing this, in Hamilton’s theory, they enhanced their inclusive fitness, or "the overall influence of an individual on the perpetuation of his genes in subsequent generations" (Porter, 1987). Thus, this redefinition of fitness in terms of gene preservation, rather than individual survival, became a founding concept in the emerging field of sociobiology.
In addition to identifying these terms, kin selection and inclusive fitness, Hamilton also determined the mathematical relationship by which they operated. Instances of "altruism" within species were not random occurrences. On the contrary, they are governed by the extent to which the two conspecifics are related. Hamilton defined the measurement of this as the coefficient of relationship, which can be stated as "the probability that an individual shares an allele identical by descent from a common ancestor with another individual" (Noonan, 1987). Thus, the degree to which an organism is related to another organism is in direct proportion to the altruism exhibited. This is due to the likelihood that the benefited individual will increase the inclusive fitness of the altruistic one. Hamilton (1964) wrote: The social behavior of a species evolves in such a way that in each distinct behavior-evoking situation the individual will seem to value his neighbors’ fitness against his own according to the coefficients of relationship appropriate to that situation.
This observation was the capstone of his theory. Underlying it are the constructs of kin selection, inclusive fitness, and the coefficient of relationship and their respective powers over behavior. This is the culmination of sociobiological thought, wherein genetic gain determines the action and response of the individual. Thus, the sterility and self-sacrifice of Hamilton’s bees are simplistically explained. The underpinnings of kin selection, inclusive fitness and the coefficient of relationship are clearly influencing these creatures to promote their genes via acts that benefit the queen.
Kin selection has been described as "a beautiful and powerful extension of Darwin’s theory" (Hardin, 1978). It is an essential corollary to Darwinian evolution, offering insight into previously misunderstood behaviors. William Hamilton has shaken the evolutionary paradigms of the past and laid foundations for future studies into evolution and behavior.