Mention extinction and most people think of dinosaurs, picturing them as hapless creatures who could not adapt to their environ-ment. In reality, they were a diverse and highly successful group of animals that inhabited the planet for 160 million years; by contrast, man has walked the Earth for only 125,000 years.
Ever since life evolved in the sea, some 3.6 billion years ago, extinction has played a vital role in our planet's natural history. Genetic mutations produce species diversification which, in turn, leads to competition; through the process of natural selection, those species that are best able to adapt to their environment will thrive while others become extinct. In the great majority of cases, this is a slow, gradual process that occurs over thousands (if not millions) of years. However, natural catastrophes, such as asteroid strikes, super volcano eruptions or other triggers of sudden climate change, can produce rapid and widespread extinctions; often associated with periods of glaciation, these mass extinctions are spaced throughout the history of our planet.
Humans, equipped with superior brain power, have imposed a new wave of extinction. Having directly out-competed Homo erectus and the Neanderthals, we now threaten the survival of other species through destruction of natural habitat, pollution of the environment, over hunting and over fishing. Recent global warming, to which we have clearly contributed, may lead to the extinction of many species and will surely have a negative effect on humans as well. By reducing our impact on natural ecosystems, we should be able to minimize man-induced extinction; nevertheless, natural extinction, essential to the balance of life on Earth, will continue and, at some point in the future, it will claim our own species.