The Handy Psychology Answer Book. Lisa J. Cohen

codes for to be passed along from generation to generation. Nonetheless, there is variation in DNA, which means that a variety of traits will be present in any population. Such genetic variation comes in part from the mixing and matching of each parent’s genes in sexual reproduction; each child receives a different combination of his or her parents’ genes. Random genetic mutations also contribute to variation in the gene pool. This means that some genes just change unpredictably as they are passed from generation to generation. Inevitably, some traits are better adapted to the environment than others. The traits that are best adapted to the environment increase the organism’s chances of surviving to pass on the relevant genes to the next generation. In this way nature picks winners and losers via the process of natural selection.

      What is Lamarckian evolution?

      Jean-Baptiste Lamarck (1744–1829) was a French biologist who contributed to pre-Darwinian theories of evolution. In keeping with the ideas of Charles Darwin’s grandfather, Erasmus Darwin, Lamarck believed in the inheritance of acquired characteristics. In other words, an animal learns a new way to adapt to the environment and these changes are then passed onto the animal’s offspring via some form of heritability. Genetic change takes place because of the animal’s behavior. The classic example involves the long neck of the giraffe. It was thought that giraffes stretched their own necks by reaching up to eat the leaves off the top of tall trees. This trait was then passed on to later generations. Similarly, mountain goats grew a thicker coat in a cold climate and then passed this trait onto their offspring.

      Although Lamarckian evolution has a kind of intuitive appeal, there has never been any evidence to support its central premise that learned behavior is directly coded into the genes, and it is not considered a scientifically valid theory. In modern evolutionary theory, genetic changes occur through random mutation. Some of these genetic mutations will improve the animal’s adaptation to the environment, though most will not. Those genes that do improve adaptation are more likely to be passed on to the next generation. Hence the environment influences reproductive success but does not act upon the genes directly.

      How does evolution affect animal behavior?

      Just as evolution shapes an animal’s physiology, it also shapes its behavior. We generally assume that animal behavior is adaptive, that it has evolved because it confers fitness on the organism whose genetic make-up produces the behavior. For example, we assume that the mating dance of pigeons—in which they strut back and forth, jut their necks in and out, and emit loud cooing noises—is adaptive. It increases male pigeons’ access to females and thus to reproductive success. This display behavior may make the male look bigger and stronger than he actually is. Females are more likely to select such males as mates because selection of large and strong males may confer an evolutionary advantage for the females’ offspring. Male displays of strength and size are very frequent strategies for access to females, evident in an extremely wide array of species, including our own. If we consider human males’ predilection for muscle cars and bodybuilding, we can see how the principles of sociobiology might indeed be relevant to the behavior of humans.

      Who is Edward O. Wilson?

      Edward O. Wilson (1929–) is considered the father of sociobiology. A professor of entomology (the study of insects) in the Harvard biology department since 1956, he has maintained a lifelong interest in the social behavior of animals. His original specialty was the social life of ants. Wilson’s great contribution was to state that the evolutionary explanation of animal behavior could be applied to the study of human behavior. He did not mean that culture and environment had no influence, only that our behavioral repertoire has its origins in our genetics and has been shaped by the processes of natural selection.

      When he first published his classic text Sociobiology: The New Synthesis in 1975, it was met with much resistance. To many people it was politically offensive because it seemed to dismiss the importance of environment. As with eugenics and other earlier movements that proclaimed the heritability of human behavior, it seemed to endorse social inequality as the natural order of things. Over the last few decades, however, sociobiology and evolutionary psychology have become more widely accepted. With advances in brain imaging technology and other methods of studying biology, our understanding of the biological underpinnings of human behavior has grown dramatically. Likewise, our appreciation of the complex interplay between genes and environment has also advanced, so that it is now accepted that recognition of the genetic basis of behavior does not have to mean that environment is irrelevant.

      As Edward O. Wilson showed, insects can have complex social behaviors, like these caterpillars who organize themselves into a circular formation.

      Why was sociobiology considered controversial when it first came out?

      Sociobiology was extremely controversial in its early days in the 1970s and 1980s. To say that a behavior had a genetic basis seemed to imply that it was morally desirable or inevitable. Further, the emphasis on genetics was seen to invalidate the importance of environment. We now know that environment and genetics interact in almost all of human behavior. While genetics may set the outer limits of behavior, environment has huge influence on the expression of behavior and even on the expression of genes themselves. Genes can be turned on and off according to environmental influences. The biggest problem with evolutionary explanations of human behavior, however, involves the profound difficulty distinguishing between proximate and ultimate levels of causation.

      What is the difference between proximate and ultimate causation?

      The ultimate level of causation refers to the behavior’s evolutionary significance; how the behavior enhances reproductive fitness. The proximate cause refers to the immediate cause of a behavior, whether that be hormonal, neurological, cognitive, interpersonal, or cultural. For example, the proximate cause of humans eating more cookies, cake, and ice cream is that people enjoy the taste; cookies, candy, and ice cream taste good. The ultimate cause involves the high caloric content of both sweet and high fat foods, which promotes physical survival in resource-scarce environments. Such environments were typical until only just recently.

      How is Darwinian evolution relevant to psychology?

      Darwinian evolution is the central explanatory framework for all of biology. All of biological science is understood within the context of evolution. Likewise, human beings are biological animals and our behavior is inextricably tied to our biology. Thus, a clear understanding of evolutionary principles is critical to the understanding of human psychology.

      However, distinguishing between proximate and ultimate causes in human beings is extremely difficult, far more difficult than it is in simple animals, like insects, whose behavior is much more closely tied to their genetics. This is because one of the most important evolutionary strategies of human beings involves our remarkably developed intelligence. No other animal on earth can learn information of such complexity and modify its behavior in such diverse ways. Therefore, due to our remarkable behavioral flexibility, it is very difficult to distinguish what behavior is learned and what is genetically based.

      If our behavior is genetically determined, where does learning come in?

      Both sociobiology and evolutionary psychology assume our behavior is grounded in our genetics. Genetics determine the range of possible behaviors and the parameters of our behavior. Much of our behavior, however, simply cannot develop without extensive training. For example, we cannot learn to read unless we are taught the necessary skills and unless we are exposed to reading materials. With the proper circumstances, our genetic makeup allows us to learn to read. In contrast, no amount of training will ever lead a cat, a dog, or a pigeon to read. Likewise, no amount of training will ever allow a human being to fly (without artificial support). Thus genetics determine the potentiality of our behavior but genetics alone cannot determine the specific outcomes for any given individual.

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