Wednesday, April 02, 2008

The Individuality, Contingency, and Historicity of Life

One objection to Darwinian conservatism is that a Darwinian view of evolved human nature opens the way to the use of biotechnology to change, or even abolish, human nature. Some conservatives worry that even if Darwinian biology denies the utopian belief of the left in human perfectibility through social engineering, this still leaves open the possibility of perfectibility through biological engineering. These conservatives share Leon Kass's worry that biotech is leading us to a "posthuman" future that will bring what C. S. Lewis called "the abolition of man."

In response to this objection, I have argued that people like Kass have exaggerated the power of biotech for changing human nature. They fail to see that biotech will always be limited in its power by the historical indeterminacy of living nature.

We commonly classify biology along with physics and chemistry as belonging to the natural sciences, which we distinguish from the social sciences such as economics and political science and the humanistic disciplines such as history. But I agree with biologists such as Ernst Mayr and Jared Diamond who argue that the fundamental distinction is between historical sciences and nonhistorical sciences, and that biology belongs to the historical sciences, along with economics, history, and political science, while physics and chemistry belong to the nonhistorical sciences.

For each kind of elementary particle studied by physicists and for each kind of molecule studied by chemists, the individual members of the class are identical. And consequently, physicists and chemists can formulate universal deterministic laws, at least at the macroscopic level. But in the historical sciences, the objects of study display a radical individuality in that each member of a class is unique. So, for the social scientist, every human society is unique, and every member of each society is unique. For the biologist, every species is unique, and every member of each species is unique. Even genetically identical bacteria grown in homogeneous conditions show unique individuality in their behavioral movements that persist over their lifespans. Consequently, social scientists and biologists can formulate probabilistic regularities but not deterministic laws. The phenomena studied in the historical sciences show emergent complexity, in that they must be consistent with the deterministic laws of physics and chemistry, but they cannot be reduced to those laws.

Consider, for example, Jane Goodall's magnum opus The Chimpanzees of Gombe. As the title suggests, this book gives a historical narrative of one unique group of chimpanzees in the Gombe Stream Preserve in Tanzania, and yet it also generalizes about probabilistic tendencies in all chimpanzee groups. So, for example, she narrates the history of the male dominance hierarchy in Gombe, which reflects the unique personalities and unique social circumstances of the Gombe chimps. She can generalize about how any chimpanzee group will tend to display a male dominance hierarchy, but she cannot predict the precise historical pathway for any particular chimpanzee dominance hierarchy. Moreover, she notices that different chimpanzee groups have different cultural traditions of behavior reflecting unique cultural histories. And now many primatologists have confirmed that chimps show complex patterns of cultural learning and tradition that resemble those of human beings. The uniqueness of each chimpanzee individual and the uniqueness of each chimpanzee group give rise to historical traditions of behavior that cannot be precisely predicted by deterministic laws.

It is true that all life depends on genes and a shared genetic code, which allow us to formulate general laws of life, and that through biotech, we can use our knowledge of those genetic laws of life to gain some power over living nature. But although genes are necessary for explaining life, they are not sufficient. And, furthermore, the complexity of genetic causality introduces historical contingency in ways that make it impossible to develop deterministic laws of behavioral genetics.

From the earliest days of genetics, beginning with T. H. Morgan, the fruit fly has been one of the favored model organisms for studying genetics. Amazingly, many of the genetic mechanisms that shape not only the anatomy and physiology but also the behavior of fruit flies are fundamentally similar to those for more complex animals, including human beings. And yet, even the fruit fly shows a remarkable flexibility in its genetics that comes from the complexity of genetic causality. There are few cases where a single gene has a single function. Most genes are pleiotropic, in that they have more than one effect. And most genes are interactive, in that the action of each gene depends on its interactions with other genes, with other molecules inside and outside its cell, and with the external world generally. Moreover, the action of the gene may depend on the life history of its cell and of the individual organism in which it resides. Rather than acting through linear pathways, as is commonly depicted in textbooks, genes form complex networks. These networks of genes influence behavior only through networks of cellular mechanisms throughout the organism, including the neural networks of the nervous system. These highly integrated networks arranged in nested hierarchies--from genes to cells to tissues to nervous systems--give even a simple fruit fly an adaptive flexibility to respond to contingent events that cannot be predetermined by deterministic laws.

The causal complexity of gene action puts severe limits on the power of biotech for manipulating genes that influence complex traits. So, for example, while we hear a lot of talk these days about "designer babies," there is no reason to believe that we will ever be able to "design" babies if that means controlling complex behavioral traits like intelligence and personality. The complexity of gene networks make it difficult, if not impossible, to use biotech to alter our genes to enhance desirable traits without bringing about undesirable side effects. If we knock out or suppress one gene because it contributes to some undesirable effect, we might discover that the same gene has other effects that are desirable. Or we might discover that the undesirable effect really depends on so many genes interacting among themselves and with so many other factors, that controlling one gene gives us no control over that undesirable effect.

Identical (monozygotic) twins--who have the same genetic constitution--are often remarkably similar, not only in their physical appearance, but also in their emotional and intellectual character. Fraternal (dizygotic) twins--who share only about half their genes--are often quite different from one another. This surely shows the powerful influence of genes on the behavioral propensities of human beings. But still, even identical twins are not really identical. For example, their fingerprints are similar and yet different.  Identical twins differ in their character traits in ways that make them distinct persons, because subtle differences in their life-history development give them different traits. These differences start even in the uterus. Most identical twins share the same placenta. But about one-third develop in separate placentas. Those who had separate placentas seem to be less similar to one another than twins who shared a placenta.

Even conjoined twins--those whose bodies are attached--show clear differences in their personalities, even though they have shared virtually identical environments as well as identical genomes. The original "Siamese twins"--Eng and Chang Bunker--were born in Siam (now Thailand) in 1811. They were born joined at the chest by a band of flesh. After their death, an autopsy showed that they had shared liver tissue. They moved to the United States, became successful farmers in North Carolina, and married two sisters. The sisters lived in separate houses. Eng and Chang would divide each week between the two homes. They had 21 children between the two of them. The brothers often fought with one another because their personalities were so different. Eng was quiet, amiable, and a teetotaler. Chang was aggressive, irritable, and inclined to alcoholism. In other words, they were individuals.

The individual uniqueness of living beings--even with individuals having the same genome--denies the popular idea that cloning produces duplicates. One motivation for cloning might be to preserve a loved one that is going to die. But this motivation is misguided because the clone would not really be identical to its progenitor. For example, pet owners might want to preserve their favorite pets by cloning them, but they would discover that the clones were not really replicas of their beloved animal. A company--Genetic Savings and Clone--was set up to sell cloning services to pet owners. They attracted great publicity a few years ago when they announced that they had cloned a cat that they named "Copy Cat." But this turned into a public relations flop when the pictures were widely published around the world. They had cloned a calico cat, and calicos have varying patterns of coloration that depend not just on genes but also on environmental cues in the mother cat's womb. As a result, "Copy Cat" did not look at all like the cat from which she was cloned. The scientists who did this work at Texas A & M University reported: "As with other genetically identical animals with multicolored coats, the cloned kitten's color patterning is not exactly the same as that of the nuclear donor--this is because the pattern of pigmentation in multicolored animals is the result not only of genetic factors but also of developmental factors that are not controlled by genotype." But that suggests that the excitement about cloning as a way of duplicating animals and humans is based on the false idea that identical genes produce identical creatures.

1 comment:

Rob Schebel said...

How many times in history have people said, "we will never be able to ......," only later to find out that indeed we can?

As Albert Einstein said, "If at first an idea does not sound absurd, then there is no hope for it."

Yes, genomic interactions are highly complex. When we alter a mouse genome to create an organism with higher intelligence than normal, we also affect the mouse's lifespan. But, given enough tinkering, we would still be changing the nature of the mouse, even if we created undesirable side-effects.

We can already use existing technologies, such as in-vitro fertlization, to make deliberate choices about the kinds of babies we have. For example, parents can choose the sex of their baby by having doctors only implant embryos of that sex in-vitro. Doesn't this biotechnology already potentially alter the way humans interact in a fundamental way? Doesn't this biotechnology potentially affect society enough that any natural right theory should be able to address it?

I think your speculation that we'll never develop genetic alterations enough to change human beings permanently is just as speculative as the notion that we will.

If a natural right theory is going to apply to universal human nature, then it needs to be broad enough to address a potential future human technology. Denying the possiblity of such a technology is a cop-out.