Anthropology: evidence for human origins

Anthropology is the science of the origin and development of humans as biological and social beings; it draws on molecular biology, cytology, anatomy, physiology, embryology, palaeontology and archaeology. In classification humans are: phylum Chordata, class Mammalia, order Primates, family Hominidae (humans and great apes), genus Homo, species Homo sapiens. Evidence of kinship. Embryological: the human embryo, like that of all chordates, forms a notochord, a nerve tube and pharyngeal (gill) slits, which later change. Anatomical: humans, like other mammals, have 7 neck vertebrae, a diaphragm, a four-chambered heart, mammary and sweat glands and 3 ear bones in the middle ear. Vestigial organs are organs that had a big function in ancestors and are reduced in humans: the tail vertebrae (coccyx), muscles that move the outer ear, and the remnant of the third eyelid. The appendix is also much reduced, but note it contains immune tissue, so it should not be called “useless”. Atavism is the reappearance of an ancestral trait in some individuals (for example very dense body hair or a tail-like outgrowth); these are rare. Genetic: human and chimpanzee DNA sequences are about 98–99 per cent identical in the regions that can be compared; the human karyotype has 46 chromosomes, those of the chimpanzee, gorilla and orangutan have 48. Human chromosome 2 was formed by the fusion of two ancestral chromosomes: it keeps the traces of fusion (a second, inactive centromere and telomere remnants). Features linked to walking on two legs: the S-shaped curves of the spine, the arch of the foot, a widened pelvis and the skull joining the spine from below.