Species that evolved from a common ancestor are bunched together under the heading genus (plural: genera). The genus Pathera contains several different species such as lions, tigers and jaguars. Biologists have named each organism with a latin name consisting of two parts; the genus follow by the species, making the lion Panthera leo. These genera are in turn grouped into families, for example the family of cats. This means that all cats, from small house cats to lions, share a common ancestor.

This is where the only human species comes into play, the Homo Sapiens; we too belong to a family of animals. Homo Sapiens long believed, and preferred to believe, that it was a species apart from animals and without brothers and sisters. This is not the case; we are all members of a large family called the great apes. Our closest living relatives are chimpanzees, gorillas and orangutans. A short 6 million years ago, a female ape had two daughters; one became the ancestor of all chimpanzees, the other is our own ancestor.

Once upon a time we had quite a few brothers and sisters. For the last 10,000 years, our species has been the only human species around. Yet the real meaning of the word human is ‘an animal belonging to the genus Homo’, and there used to be many others. Humans first evolved in East Africa about 2,5 million years ago from an earlier genus of apes called Australopithecus. From this first human species, many other evolved such as Homo Erectus, Homo Soloensis, Homo Neanderthalensis and of course Homo Sapiens. So how did we end up being the only human species on earth today? There are two theories; the Interbreeding Theory and the Replacement Theory.

According to the Interbreeding Theory, when Sapiens spread into Neanderthal territory, the two species bred and merged together. If this theory is correct, today’s Eurasians are not pure Sapiens, but a mixture of Sapiens and Neanderthals. Similarly, when Sapiens reached East Asia, they interbred with the local Erectus.

The Replacement Theory suggests an opposing story; one of incompatibility and possibly even of genocide. According to this theory, Sapiens and other human species had different anatomies and little sexual interest in each other. The two species would not be able to produce fertile children because the genetics differed too much. The two populations remained completely separated and as the other human species died out, or were killed off, the genes died with them.

Reading tip: Sapiens (A Brief History of Humankind) – Yuval Noah Harari