Excerpt. © Reprinted by permission. All rights reserved.
Chapter One: The Developmental Kitchen
What is the use of a new-born child?
From Egg to Adult
How and why does each human grow up to be a unique individual? What role do genes play in shaping behavior and personality? Are people's characters fixed early in life or can they change as adults? How does early experience affect sexual preferences? Why do children play? These are all questions about behavioral development -- the lifelong process of growth and change from conception to death, which is central to an understanding of human nature.
After the microscope was invented in the late sixteenth century, people gazed with excitement at the structure of the fertilized egg and thought they could see dimly within it the makings of an adult. Some even saw a small person crouched inside the head of each human sperm -- or, if their prejudices were different, inside the unfertilized egg. It seemed satisfying to think of growing up as merely getting larger. But the satisfaction was deeply misplaced. Most animals, including humans, do not just grow -- they develop. Everybody is the product of development.
The fertilized egg from which each person develops is barely visible to the eye. The adult human body consists of millions upon million of cells doing different things. Nerve cells, skin cells, and white blood cells, for example, all contain the same set of genes but are highly specialized for particular tasks. The cells are integrated within organs devoted to specific functions such as digesting food, pumping nutrients and oxygen to remote corners of the body, and integrating body movement in ways that serve the overall need of the whole individual to survive and reproduce. How does an organism such as a human transform itself from a tiny single cell into a self-aware individual with organs and cells all arranged in the right place at the right time?
Each human is a product of essentially the same developmental processes. And yet each human is also a distinctive individual. As Friedrich Nietzsche wrote: "At bottom every man knows well enough that he is a unique being, only once on this earth; and by no extraordinary chance will such a marvellously picturesque piece of diversity in unity as he is, ever be put together a second time." Understanding behavioral development means understanding the biological and psychological processes that build a unique adult from a fertilized egg. It also means understanding how these developmental processes have themselves evolved, and how their features can be viewed in terms of their biological design properties. But it does not mean trying to explain human behavior in terms of the conventional opposition between nature (genes) and nurture (environment).
"Nature" and "Nurture"
In his autobiography, Charles Darwin expressed this view about the development of human mental faculties:
I am inclined to agree...that education and environment produce only a small effect on the mind of any one, and that most of our qualities are innate.
A contrasting view of how each person's mind is formed was expressed by the seventeenth-century philosopher John Locke:
Let us then suppose the mind to be, as we say, white paper, void of all characters, without any ideas; how comes it to be furnished?...Whence has it all the materials of reason and knowledge?...To this I answer, in one word, from experience; in all that our knowledge is founded and from that it ultimately derives itself.
Many people end up believing in a bit of both -- some qualities reflect "nature" and some "nurture." Attitudes about whether a skill reflects an unchangeable part of the child or the way the child has been taught may depend on how essential that skill is thought to be. Parents who would balk at the suggestion that their children's personalities and behavior are "all in the genes" can simultaneously be attracted by the notion that more exotic talents, such as exceptional abilities in music or mathematics, are inherited or "innate." Ambitious parents who incline to this view may feel less compelled to pressure a child who displays no obvious flair for the subject. After all, the argument goes, you've either got it or you haven't, and if you haven't, then no amount of hard work or practice can help. The selfsame parents will usually adopt a quite different view of development if their children are found to be deficient in a skill such as reading. Now the focus will switch to environmental influences. Their children are useless at music because music does not run in the family, but they cannot read well because their teachers are incompetent.
Attitudes toward development also change greatly with fashion and with shifts in ideology. For many years after the Second World War the mere suggestion that genes influence human behavior was regarded as distasteful -- largely, and understandably, in reaction to the appalling abuses of science that culminated in genocide by the Nazis. Abuses were also found on the opposite side of the ideological divide. Two years after the Russian Revolution, Lenin is said to have paid a secret visit to the laboratory of the great physiologist Ivan Petrovich Pavlov to find out if Pavlov could help the Bolsheviks control human behavior. Lenin believed that individualism would interfere with his plans for a Communist state. Pavlov told him that "natural instinct" could be abolished by conditioning -- a form of learning. So congenial was this opinion to Lenin that Pavlov's position in the Soviet Union was thereafter protected, despite his not being a Communist. In 1950, long after Pavlov's death, a big government-sponsored scientific congress devoted to his teaching was held in Moscow. The party line was that man could transcend heredity and be controlled by education. A second prong in the same Stalinist program was to enforce as dogma the view that all acquired characters were passed on to subsequent generations. Under the advocacy of this dogma by T. D. Lysenko in the late 1940s, Soviet genetics effectively ceased to exist.
One cynic commented that the "environmentalists seem to believe that if cats gave birth in a stove, the result would be biscuits." Since then, the pendulum has swung a long way in the opposite direction, and nowadays it sometimes seems as if almost any aspect of human behavior or physiology can be accounted for by genes alone. With increasing frequency the media report the discovery of a gene "for" some distinct human characteristic, such as learning foreign languages, athletic prowess, or male promiscuity.
It is obvious that experience, education, and culture make a big difference in how people behave, whatever their genetic inheritance. Yet behavioral and psychological development is frequently explained in terms of the exclusive importance of one set of factors, either genetic or environmental. Such firmly held opinions derive in part from a style of advocacy common to most scientific debates. If Dr. Jones has overstated her case, then Professor Smith feels bound to redress the balance by overstating the counterargument. The confusions are amplified because of the way in which scientists analyze developmental processes. When somebody has conducted a clever experiment demonstrating an important long-term influence on behavior, he or she has good reason to feel pleased. It is easy to forget about all those other influences that they had contrived to keep constant or that play no systematic role. Consequently, debates about behavioral and psychological development often degenerate into sweeping assertions about the overriding importance of genes (standing in for "nature") or the crucial significance of the environment (which then becomes "nurture").
Design for a Life
The various stages of an individual's de