Human

Homo sapiens

Human (Homo sapiens) is a species in the genus Homo, family Hominidae, order Primates.

Scientific classification

Description

Homo sapiens is the only surviving species of the genus Homo. Adults typically stand between 1.5 and 1.9 metres tall and are distinguished from other great apes by an obligate bipedal gait, a relatively hairless body, a shortened face beneath a high forehead, and a brain averaging about 1,300 cubic centimetres — roughly three times that of a chimpanzee of comparable body size.

The skeleton is extensively remodelled for walking on two legs: the pelvis is short and bowl-shaped, the spine carries a lumbar curve, the femora angle inward toward the knees, and the foot has lost the opposable big toe that other apes use for grasping. The hand retains the ape grasping plan but adds a long, strongly muscled thumb that can be brought against each fingertip, giving the precision grip used in tool-making.

Distribution and habitat

The species originated in Africa and is now the most widely distributed large land mammal, occupying every continent including year-round research stations in Antarctica, as well as low Earth orbit continuously since 2000. Populations persist from sea level to permanent settlements above 5,000 metres in the Andes and on the Tibetan Plateau, sustained less by physiological adaptation than by clothing, shelter, fire and food storage.

Biology

Development is unusually slow. Gestation lasts about nine months, infants are born helpless and neurologically immature relative to other primates, weaning occurs late, and sexual maturity is not reached for more than a decade — a life history that concentrates learning into a long dependent childhood. Females undergo menopause and commonly survive decades beyond their last reproduction, a pattern shared with few other mammals, notably some toothed whales.

Language is the species' most distinctive behavioural trait: a learned, generative system with recursive syntax, used by every known human population and not clearly paralleled elsewhere in the animal kingdom.

Taxonomy

The species was described by Linnaeus in 1758, who — unusually — designated no type specimen; he is himself generally treated as the lectotype. The closest living relatives are the chimpanzee and bonobo, with which Homo sapiens shares a common ancestor around six to eight million years ago. Neanderthals and Denisovans were distinct populations that interbred with the ancestors of many living people; their DNA persists in modern genomes.

References

• Linnaeus, C. (1758). Systema Naturae, 10th edition.
• Lieberman, D. E. (2013). The Story of the Human Body. Pantheon.