The earth is facing the prospect of a mass extinction of most of the species on earth. Unlike previous mass extinctions caused by “natural” events, such as the crash of a huge meteor into the earth, this one can be prevented. It is precipitated by the destruction of the habitat of other species by a single species, homo sapiens—humans. Scientists have adopted various strategies to persuade Americans that humans have to change their ways or there will be horrible consequences for the planet and all who live upon it. It is difficult, however, for most people to understand the relationship between the well-being of their grandchildren and the extinction of a species of insect in the Brazilian rain forest that scientists may not even have had the opportunity even to name.
A paleontologist at the American Museum of Natural History in New York, author Niles Eldredge is the co-discoverer with Stephen Jay Gould of the theory of punctuated equilibria, a theory that changed how paleontologists looked at evolution. In Dominion: Can Nature and Culture Co-exist?, Eldredge has a new twist. He does not directly call upon his readers to support environmental legislation, make donations to a fund to preserve land in South America, or change their consumer habits. His strategy is to approach the issue more indirectly by posing it in the form of questions about the future of the human species. What is the future of the human species? Will that future be determined by social evolution or biological evolution?
Eldredge divides the future of the human species into three phases, although he is extremely vague about the boundaries between the phases. The first phase is the immediate future, the future he sees dominated by the threat of war, famine, and civil unrest. This is the future controlled by social and political decisions, and ranges in time from tomorrow up to perhaps a few hundred or even a few thousand years. Economics, sociology, and political science must supply the answers to the questions raised about this future, not biology. Among the immediate problems facing the human race is avoiding the “Malthusian trap.” At the end of the eighteenth century, Thomas Malthus warned that if the human population was unchecked, it would grow faster than its food supply. The result would be mass starvation. Charles Darwin used this idea in developing his theory of evolution. Thanks to the Industrial Revolution, international migration, and the Green Revolution in agriculture, the human capability to increase food supply has kept up with population increases (although famines still occurred because of local weather conditions, political upheaval, or problems in distribution). Nevertheless, with a population approaching six billion by the end of the twentieth century, social and technological solutions must be found to increase food supply or to limit population growth. Eldredge assumes that a combination of solutions will be found in the immediate future that will stabilize the human population at about ten billion without serious problems; if not, the rest of his book is moot.
As we go much further out in time, we enter the long-range future, the future defined by evolution. It is measured in hundreds of thousands, even millions of years. Gen- erally, most terrestrial species survive for only a few million years, so in normal circumstances the long-range future would be marked by the evolution of the human species into a new species—but Eldredge is emphatic that homo sapiens is not a normal species. What will not happen, according to Eldredge, is biological evolution of humans through natural selection. The diversification necessary for speciation requires geographical isolation, so that any beneficial mutation could take root and not be swamped. That will not happen in the future.
What might happen is human-directed biological evolution. Genetic engineering is making rapid progress. Conceivably, a combination of genetic engineering and enforced isolation of the resulting individuals to prevent them from interbreeding with those unlike themselves could produce a new species. Since it could only occur if humans were under some sort of despotic control, Eldredge rejects this alternative. He thinks it is too horrible for humans to allow to happen. Given the past history of humans, he is confident that the future will include technologically based cultural...