What is extinction?
Extinction is the permanent end to the existence of a species. Through the vast expanse of geological time, extinction has been the fate of most kinds of living things on earth. The background rate of extinction has been more or less constant at about one species per million each year. New species arise at about the same rate. From time to time a mass extinction event occurs.
Extirpation means the loss of a species in a local area. For example, the tuatara (a lizard-like reptile) has been extirpated from New Zealand’s North and South islands, but small populations still survive on island sanctuaries.
Ideas about extinction
The concept of extinction, at least in Western cultures, was accepted only about 200 years ago. Before that, it was assumed that each species was permanent and had existed for as long as the earth had. But as more fossils of unusual animals were unearthed, the idea that groups of these animals were still living in remote areas became untenable. By 1800 AD it was realised there were simply not enough places left for large, extinct species such as mammoth and giant sloth to hide.
Investigating extinction: Georges Cuvier
Naturalist Georges Cuvier, working in Paris around the beginning of the 19th century, realised that many fossils were of forms that no longer existed. The fossil record showed that whole groups of animals had become extinct in Europe and elsewhere. Cuvier developed methods to reconstruct the appearance of extinct species, by comparing the fossils or bones of extinct species with related existing species.
Richard Owen and New Zealand’s moa
In the late 1830s, Richard Owen in England made the British public aware of extinction, and extinct animals. On the basis of a single piece of bone sent from New Zealand, prompted by John Rule, the bone's owner, Owen deduced that huge birds related to ostriches once lived there. This idea was much publicised, and Owen’s reputation was partly founded on his series of studies of these birds, named moa by Māori. Owen named them Dinornis, meaning strange or striking bird.
Moa become extinct
Meanwhile, no living moa were found. This lack of live moa in New Zealand, like that of live mammoths and dinosaurs anywhere in the world, established the reality of extinction. Their bones or fossils remained, but the living creatures are gone. Owen’s widely distributed pamphlet prompted colonists in New Zealand to send a steady stream of bones to England. New Zealand was one of the first places where debate over extinction was part of public and scientific life.