Ecological Status of Modern Humans

Human beings (species Homo sapiens) evolved between 100,000 and 200,000 years ago (see Human Evolution). We are an omnivorous species, which means that we are able to consume a wide variety of plants, animals, fungi, and even microbial foodstuffs, depending on cultural norms (that is, what local society deems appropriate to eat) and availability. Over at least the past 2.5 million years (the date of the oldest known tools in the archaeological record), human beings have come to rely more and more on culture—learned behavior—rather than purely anatomical biological adaptations for "making a living"— that is, for obtaining the sources of energy and nutrients necessary to life. Increasing reliance on culture over purely natural adaptations has greatly altered humanity's relation to the natural world.

Like all other species in the history of life, all early species of hominid were closely connected with the world's ecosystems. Specifi cally, all species in the entire history of life are divided up into small, localized populations that form parts of the local ecosystem. This means that local populations of, for example, squirrels will be relying on the acorn production of the local oak trees as one of their sources of food; in turn, local species of hawks and owls will be preying on the squirrels, and so forth. All the local populations of different species are interacting in different ways in a complex network involving the flow of energy and nutrients from one population to another. The way in which each population goes about obtaining matter and energy is what is meant by the expression "its ecological niche."

Generally speaking, the way that local populations obtain their energy, and the way that their adaptations match up with existing resources, determine the number of individuals of that species population that can survive in any local ecosystem (this is the so-called carrying capacity of the local ecosystem). All hominid species, including the earliest members of our own species, Homo sapiens, have lived in this fashion—that is, as local populations playing roles (having a "niche") in the local ecosystem. Indeed, peoples known as hunter-gatherers still exist on the planet, and their preagri-cultural mode of life corresponds closely to the original ecological mode of existence of early humans. It must be noted, however, that modern humans have driven most hunter-gatherers to extinction, and the few remaining groups (such as the San ["Bushmen"] peoples of southern Africa and the Mbuti ["Pygmies"] of equatorial Africa) no longer live purely hunter-gathering existences; they are, at least culturally speaking, poised on the brink of extinction.

The invention of agriculture some 10,000 years ago changed the ecological status of humanity in a momentous fashion. No longer limited by the available productivity of the local ecosystems, with the domestication of plants and animals, humans effectively took charge of the production of all their food and nutrient needs. Nor does the invention of agriculture represent a simple modification of the human ecological niche: for what the coming of agriculture really did was to outright abolish the human ecological niche. Consider what it is to plant a field with one, two, or at most three plant species: it means clearing of the land (chopping down trees, removal of shrubs, brush, and native grasses) and preventing their return, while the one or two desired crops are allowed to grow. Native plants attempting to reclaim the land are now considered "weeds," interlopers in what was once their own territory. Thus, in effect, with the arrival of agriculture, humanity declared war on the local ecosystem.

No longer relying on the productivity of the local ecosystem, humans in effect had also declared their independence of it. Thus, a mere 10,000 years ago, Homo sapiens became the very first species in the entire 3.5-billion-year history of life effectively to step outside of the local ecosystem. One result of that step was a rise, slow at first but ever accelerating, even now, in human population numbers: no longer controlled by the productivity (carrying capacity) of local ecosystems, and despite the occasional devastating bouts of famine in human history, human numbers have skyrocketed from some 5 or 6 million 10,000 years ago (at the dawn of agriculture) to more than 6 billion at the recent turn of the new century—one of the causes of the present-day Sixth Extinction.

But recently there has been still another change in the human ecological condition. Over the past 10,000 years, as our numbers have grown so extraordinarily high, as we have spread around the globe, and in particular as our capacity for communication has so dramatically improved, we find ourselves as the only species in the history of life that maintains eco nomic connections with each other over truly vast distances. Some other species—such as some fruit flies—also have a worldwide distribution, brought about by the spread of humans around the globe. But while fruit fly genes can spread throughout the globe as reproductive connections are occasionally replenished, what fruit flies eat in Tokyo has little to do with what their relatives are eating in New York.

But we are different. We exchange more than $1 trillion worth of goods and services among ourselves every day. This too is very new, this economic integration of our species. It implies that, as an integrated economic entity, our species after all must be part of some larger-scale economic system—the first species in the history of life to be part of an economic system. And what is that system—as it clearly cannot be the local ecosystem? Some biologists and biologically inclined economists now believe that Homo sapiens is actually the first biological species to act as a component with the entire biosphere—the totality of all the earth's ecosystems.

In any case, the ecological status of our species is unlike that of any other species that has ever lived.

—Niles Eldredge

See also: Agriculture, Origin of; Ecology; Economics; Ecosystems; Homo Sapiens; Human Evolution; Population Growth, Human; Sixth Extinction

Bibliography

Cohen, Joel E. 1995. How Many People Can the Earth Support? New York: W. W. Norton; Eldredge, Niles. 1995. Dominion. New York: Henry Holt; Eldredge, Niles. 1998. Life in the Balance: Humanity and the Biodiversity Crisis. Princeton: Princeton University Press; Kennedy, Paul. 1993. Preparing for the Twenty-first Century. New York: Random House.

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