Robert Trivers

(1943 - )

Compiled by Jared Perrine (May 1999)

Trivers Biography
Time Line

Beneath the wild, infuriating, unpredictable personality of one of the countries leading sociobiologists, Robert Trivers has an "uncannily perceptive" and an "acute, encompassing mind" (Bingham, 1980). Having started in the field of science by writing childrens books, his remarkable progression from Harvard law to Darwinian law is one that has shaped the boundaries of the theories of natural selection, ethics, and biology in general for years to come. The unpredictable Trivers seems a walking contradiction in ways that will be very evident after studying his actions in life, but uncontradictingly his contributions to the field of science has earned him the title of one of this centuries "Mavericks of the Mind" (Brown, 1993).

Trivers was born in 1943. His scientific life began in 1964 when as a Harvard undergraduate he had a nervous breakdown and was denied admissions to the Unviversity's Law program. A year later he graduated from Harvard with a degree in United States History. For the next two years he wrote children's books dealing with science school curriculum. Because of his lack of knowledge in this subject area, Trivers researched the scientific literature related to motivational systems and in 1966 discovered his strong opposition to the emerging, popular idea of group fitness. A year later he returned to Harvard to pursue a Masters in Biology and by 1972 had earned his doctorate and developed his theory of Reciprocal Altruism (Bingham, 1980). After publishing theoretical papers on his "altruistic theories" Trivers was offered a teaching position at Harvard, where he worked from 1973 to 1978. At the beginning of this service, Trivers coauthored a paper on population ratios with Willard which became very popular and is now know as the Trivers-Willard Effect (Trivers, 1973). Since 1978, Trivers has been teaching at the University of California, Santa Cruz and has written many papers, introductions to books, and remaines a very active theoretician (Brown, 1993).

Trivers is a sociobiologist. He asks questions like: Are social behaviors genetically inheritable, evolving over time like physical characteristics? Genes are considered a major determinant of social behavior. Trivers thinks it is inherently impossible to assign percentages to genetically hard wired and environmental factors that play in behavior because in order to figure it out you would have to specify the full range of environmental contingencies and the full range of genetic contingencies, and that is what he calls, "hopeless" (Brown, 1993). He and most sociobiologists argue that there is no way to see how much of human behavior is genetically hard-wired, or how much is environmentally determined. Nevertheless, the biological influence is critical.

Trivers has offered theoretical accounts of social theory, such as: natural selection, group selection, kinship, sexual selection, the primary sex ratio, and so on. The following are Trivers' most influential contributions to science: The Trivers-Willard Effect, and the concept of Reciprocal Altruism.

Reciprocal Altruism: Old models that tried to explain altruism took the altruism out of altruism. In Darwinian terms, altruism doesn't seem to make very much sense. Why would one being risk it's own fitness for that of another (Singer, 1994), since the genes for such kindness would be lost to the next generation.

Reciprocal Altruism is reflected by the old saying, "you scratch my back, I'll scratch yours". Basically it is possible to benefit another being with seemingly no benefit to yourself if there is a probability of the favor being reciprocated. The benefit comes in the future when the individual helped reciprocates with either the same action or one of a higher level of benefit (Brown, 1993).

Why not cheat? Receive the benefit and not reciprocate. It seems it would be beneficial to cheat. Actually there are two forms of cheating: gross and subtle. Gross Cheating is defined by Trivers as when "the cheater fails to reciprocate at all, and the altruist suffers the costs of whatever altruism he has dispensed without any compensating benefits", and Subtle Cheating is defined as when the relationship "involves reciprocating, but [one party is] always attempting to give less than one was given" (Brown, 1993). So why not cheat? Why is it beneficial to not cheat? Why does selection favor the noncheater? Because the benefits of cheating will not out weigh the adverse effects on life which could happen if the altruist decides not to have anything to do with the cheater. For if the altruist decides to separate itself from the cheater, the cheater not only loses a future reciprocation, it loses the relationship upon which many exchanges could take place between itself and the altruist. Selection favors the noncheater for this reason; this relationship of seemingly altruistic exchanges.

Altruistic behaviors are greatest when "there are many such altruistic situations in the lifetime of the altruists, when a given altruist repeatedly interacts with the same small set of individuals, and when pairs of altruists are exposed 'symmetrically' to altruistic situations", and some of these behaviors are: "helping in times of danger, sharing food, helping the sick or wounded, sharing implements, and sharing knowledge". Such, we have done in our history, perhaps this is why our system of behaviors and motivations are so complex, but that is the good thing about reciprocal altruism- it is "developmentally plastic" or changeable. And this is why reciprocal altruism is the law for the system of relationships we call ethics (Brown, 1993).

Trivers-Willard Effect: Typically, there is thought of a 50/50 sex ratio in local breeding populations, but under certain conditions this is not true. Graph Under certain conditions natural selections favors deviations from the typical 50/50 split. In 1973 Trivers and Willard theorized that a mother can adjust her offspring's gender ratio to maximize her reproductive success. Consider first that a mother in good condition will produce offspring in better condition. Second, consider that condition affects male reproductive success more than female reproductive success. For a male in top condition will exclude other males from reproducing and, therefore, will impregnate more females himself. So, a mother in good condition that produces a son will have more surviving offspring than if she produced a female. Trivers found that as maternal condition declines, the adult female tends to produce a lower ratio of males to females. "This is due to natural selection driving the sex ratio to favor the sex that will best reproduce in a poor condition - the female" (Trivers, 1973).

Trivers once said, "psychology, law, economics, anthropology, psychiatry, psychology, and sociology would all benefit, from a strong injection of evolutionary thinking... twenty years from now, they're going to be willing to hear my thoughts on religion and all sorts of crackpot stuff at national meetings". He was correct, but how could anyone really not incorporate one of the most important ethical theories of the century into things as important as religion and philosophy. After all, ethics are intertwined with everything in our lives.

With words like religion and ethics as the forefront of themes to Trivers theories, remember his words, "[I'm] not winning souls for eternity; just winning minds for Darwin" (Bingham, 1980).

Time Line
1943 Birth
1964 Breakdown at Harvard (denied in law school)
1965 BA from Harvard in US History
1965 Wrote childrens books
1966 Started to discard Group Fitness construct
1967 Back to Harvard
1969 Visited Jamaica for the first time
1972 Ph.D in biology . Developed concept of Reciprocal Altruism
1973-78 Taught at Harvard
1973 Postulated Trivers-Willard Effect
1978-99 Taught at UC Santa Cruz
1979 Joined the Black Panther Party
1985 Published a text book, Social Evoluation
1994 Published an article in Ethics
1998 Wrote Genetic Conflicts in Genomic Imprinting

Bingham, Roger. (1980) Trivers In Jamaica. Science 80, March/April: 56-67
Brown, Jay. (1993)
Mavericks of the Mind. California: The Crossing Press.
Singer, Peter. (1994) Ethics. New York: Oxford University Press.
Trivers, Robert. (1973) Natural Selection of Parental Ability to Vary the Sex Ratio of Offspring. Science, 179: 90-92.
Trivers, Robert. (1985) Social Evolution. California: Cummings Publishing Co.

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