(a) Human adolescent growth spurt (10 marks) (b) The losses and gains of erect posture (10 marks) (c) Is race a valid and…

(a) Human Adolescent Growth Spurt The adolescent growth spurt is the sharp acceleration in height and weight at puberty, after a steadily falling childhood growth rate. Humans are unusual among primates in having a clear spurt. Activation of the hypothalamic-pituitary-gonadal axis raises gonadal steroids, which amplify growth hormone and IGF-1 secretion.

Timing shows sexual dimorphism. Girls start around 10-11 years and reach peak height velocity (PHV) near 12 years, at about 7-8 cm a year. Boys start around 12 years and peak near 14 years, at about 9-10 cm a year; two extra years of pre-pubertal growth leave them taller. The spurt runs alongside the Tanner stages of puberty. Rising oestrogen and androgens finally cause epiphyseal fusion, ending longitudinal growth (skeletal maturation), which wrist X-ray bone age reveals. Barry Bogin links the spurt to a prolonged childhood for learning. Undernutrition delays and blunts it.

(b) The Losses and Gains of Erect Posture Habitual bipedalism, seen in Australopithecus afarensis (Laetoli footprints, about 3.7 million years ago; "Lucy", about 3.2 million years ago), brought gains and costs.

Gains: the hands were freed for tool-making, carrying infants and food, and food sharing. The raised head widened the view over open savanna. Walking is energy-efficient over long distances compared with the knuckle-walking of apes. The upright body also presents less surface to the midday sun and gains convective cooling.

Losses: the pelvis became short and basin-shaped, narrowing the birth canal and creating the obstetric dilemma with large-brained infants, hence difficult labour and assisted birth. Gravity on the spine causes lumbar lordosis, back pain and disc prolapse. Hip and knee osteoarthritis, flat feet, hernias, varicose veins and haemorrhoids also follow.

(c) Is Race a Valid and Biologically Meaningful Concept? Modern anthropology rejects biological race. Typologists such as Linnaeus, Blumenbach and Coon sorted people into fixed, ranked types using skin colour, hair form and cranial index. Coon's view (The Origin of Races, 1962) was opposed by Dobzhansky's population approach.

Population genetics refutes discrete races. Lewontin (1972) found that about 85% of human genetic variation lies within local populations and only about 6% separates the traditional races. Variation is continuous and clinal, as Livingstone's dictum puts it: there are no races, only clines. Traits follow separate geographic gradients, so they do not cluster together. The sickle-cell (HbS) allele, for example, tracks malaria exposure in Africa, the Mediterranean and India, not skin colour or "race".

Conclusion: race is not a valid biological unit. It is a social construct with real social consequences.

(d) Descent Groups A descent group is a corporate kin group whose members trace descent from a common real or putative ancestor. It holds property, regulates marriage (exogamy), organises ritual and gives political support.

A lineage can demonstrate genealogical links to its apical ancestor; a clan is a larger group that only stipulates descent, often from a mythical ancestor. Where a society divides into two halves, each half is a moiety; where into several clan clusters, each is a phratry. Evans-Pritchard described segmentary lineages among the Nuer.

Unilineal descent follows one parent: patrilineal (Nuer, Gonds) or matrilineal (Khasi of Meghalaya, Nairs of Kerala). Cognatic (bilateral or ambilineal) descent is traced through both sides, as among foragers or in modern urban families, and so forms no sharply bounded group.

(e) Modes of Subsistence Modes of subsistence are the ways societies obtain food and so shape population density, mobility and social organisation.

Foraging (hunting-gathering) uses wild resources, with small mobile egalitarian bands, as with the Onge and Jarawa of the Andamans. Pastoralism rests on herd animals and mobility or transhumance, as among the Toda and Bakkarwals. Horticulture is small-scale cultivation with hand tools, often shifting (jhum) cultivation as in Nagaland, supporting villages and clans. Intensive agriculture uses plough, irrigation and terracing to generate regular surplus, enabling dense populations, specialised labour, stratification and the state. Industrial and urban economies depend on wage labour, fossil-fuel energy and markets.

The choice depends on ecology, technology and history.