Historical Natures

Historians and Nature

By Donald Worster

We can hardly speak of evolution without mentioning the name of Charles Darwin. So I will begin with the founding father. Early in 1834 the young naturalist Darwin left his ship’s berth aboard the H.M.S. Beagle to venture across the grassy plains of Patagonia. Those plains left an impact on his mind that was almost as powerful as the impact of the more famous Galápagos Islands. Despite their dusty monotony, the plains offered him vivid glimpses into the deep, unknown history of life on earth–vestiges of creatures now extinct and ways of life now vanished.

At Port St. Julian, where grassland meets ocean, he discovered the fossilized remains of a large mammal. It was the first time in his explorations that he had come across such ancient bones. They turned out to be bones of an extinct giant llama, not the mastodon he supposed, but unmistakably they spoke of “the changed state of the American continent,” where species succeeded species, throwing “more light on the appearance of organic beings on our earth, and their disappearance from it, than any other class of facts.” The grasslands forced Darwin to confront the power of nature, the mutability of organisms, and the ecological revolutions that had occurred in the past.

Darwin is surely the most influential scientist in modern times, not only as the founder of evolutionary biology and ecology but also as the inspirer of anthropologists, economists, psychologists, and philosophers. Despite the stubborn resistance of many religious people, his science has profoundly reshaped our modern worldview–indeed, evolution is its very foundation. His book On the Origin of Species, published in 1859, argued that life has evolved by wholly natural processes, without any supernatural intervention. Every organism, he pointed out, varies in some degree or trait from all other organisms, and that variability is basic to evolution. In a world of limited resources, variation must compete against variation, and those individuals that survive and leave offspring provide the next generation of organisms that, in turn, may leave heirs of their own. The less successful–those less fitted to their environment–eventually vanish into the earth, unless conditions suddenly change in their favor.

Today we know far more about the history of life than Darwin did, although the main outlines of his theory of evolution through natural selection have held up amazingly well. Since the discovery of the structure of DNA in 1953, scientists have learned how to track natural selection and other forms of evolution back in time millions of years. Through the science of ecology we know a lot more about how complex ecosystems evolve, often in response to large-scale and sometimes sudden and violent environmental disturbance by shifting climatic regimes, drifting continents, and crashing meteors. And not least in significance, we have directly observed what Darwin did not actually see in Patagonia or the Galápagos Islands: evolution actually taking place, not in some long ago period and at imperceptible rates, but in the present at a measurable pace.

We also know much more than Darwin did about how humans have evolved in mind and body, and we are beginning to establish scientifically how much our behavior is rooted in our genes, so that we are not solely the product of society or culture. Edward O. Wilson was not the first, back in 1975, to argue that our behavior has much in common with other species. But today that argument no longer meets such fierce resistance. The study of evolutionary psychology is making significant gains toward explaining how the brain has evolved and how it shapes what we see and how we behave. Today, more and more social scientists, following the lead of the natural scientists, are eagerly pursuing neo-Darwinian theories at the level of the individual mind, group interaction, and even religion and culture.

Human beings, those scientists tell us, are not born into this world with minds like blank pages, waiting to be written on by others–family, church, politicians, advertising executives. We emerged as a species a half-million years ago, during the Pleistocene, and ever since we have followed what Wilson calls “epigenetic rules,” which he defines as “innate operations in the sensory system of the brain. These are rules of thumb that allow organisms to find rapid solutions to problems encountered in the environment. They predispose individuals to view the world in a particular innate way and automatically to make certain choices as opposed to others.”

This is not to say that our genes explain every bit of human behavior. In many species, evolution can be cultural as well as biological, as Darwin himself realized and modern scientists agree. Cultural beliefs and ideas–or what some call “memes,” the cultural counterpart to genes–pass from individual to individual or from group to group or are selected for survival. Particularly in the case of Homo sapiens that process of cultural evolution deserves at least an equal place alongside those of biological evolution.

The anthropologist Clifford Geertz has defined culture “as a set of control mechanisms–plans, recipes, rules, instructions (what computer engineers call ‘programs’)–for the governing of behavior.” Those control mechanisms can be a powerful means of survival–more rapid and flexible in their response to environmental change than genetic variation alone.

Human evolutionary theory thus rests on the concept of a “dual inheritance,” in which genes and cultures both are powerful determinants and each co-evolves with the other. We can distinguish cultural change from genetic change and can see how cultural change can follow an independent path from genetic change, but no great or eternal chasm separates them. Over time, genes and cultures interact repeatedly, constraining or reinforcing each other, forming the dual inheritance that shapes the life ways of the human organism.

If ever there was a scientific theory that is fundamentally historical, that purports to explain change over time, it is evolution through natural selection and its corollary, humankind’s dual inheritance. Yet I have to admit that my fellow historians, teaching in history departments and professing to study that process of change, have been highly resistant to evolutionary theory. Why has that been generally so? Why have historians insisted on drawing a rigid boundary separating culture from nature? And what are the possibilities for overcoming this separation?

The good news is that the field of environmental history, which has been emerging over the past two or three decades, has successfully contested the old dualism that separates historians from the natural sciences. Environmental historians focus on the relations that humans have carried on with the rest of nature. They take for granted that humans are part of the natural world and that historians should make history more truthful by placing human life in that broader context. In contrast to social or political historians, environmental historians read books and articles on evolution and ecology and have been trying to bridge the gap separating them from the natural sciences.

So far, however, environmental historians have focused mainly on the human impact on nature–i.e., how humans have changed the land, exploited natural resources, and replaced the wilderness with cities. Let me give you an example that represents an effort to bring evolution into history but does so by emphasizing the growing human impact on evolution.

In 2003 Edmund Russell, a historian at the University of Virginia, published an important essay entitled “Evolutionary History.” He begins by noting that evolution can occur through artificial selection, like the breeding of dogs or cattle, as well as through natural selection. Darwin, Russell reminds us, began his book On the Origin of Species by comparing the two kinds of selection. He observed how plant and animal breeders change their domesticated plants and animals and then concluded that nature does for the whole earth what the cattle breeder does with his livestock. Artificial selection led him to natural selection. However, Russell turns Darwin’s reasoning around to show that what the cattle breeder does for the farm, humans are doing for the whole earth–guiding evolution to suit their needs. The chasm between what is natural and what is artificial vanishes, and in Russell’s view the whole environment is becoming increasingly a product of human intervention.

Source @ The American Scholar