It was formerly believed that domestic life everywhere was organised around a married pair and their offspring. This combination of people, called the nuclear family, is still popularly regarded as a minimal unit of social organisation. According to Linton (1949, p. 21), the combination of father, mother, and child is the "bedrock underlying all other family structures". Murdock (1967) found the nuclear family in each of 250 societies. He concluded that it was universal because it fulfills vital functions that cannot be carried out as efficiently by other means.

Despite these arguments, the weight of opinion has shifted in recent years against the proposition that the nuclear family is the elementary building block of scocial structure (Adams, 1968; Morgan, 1972).

The fact that chimpanzee grammatical competence stays below the level of a two- or three-year-old child and that a huge communication gap persists between chimpanzees and humans should cause no surprise. This gap is precisely what one should expect of an ape. There is no reason to conclude, however, that a similar gap existed between humans and our protohuman hominid ancestors. I cannot agree with Noam Chomsky when he writes: "there is no significant evidence of continuity, in an evolutionary sense, between the grammar of human languages and animal communication systems" (1973:123).

(Marvin Harris, Culture, people nature: An introduction to general anthropology, Harper & Row, 1985).

J. T. Robinson advanced the first theory to explain these differences. He proposed that the graciles were primarily meat-eaters and the direct ancestors of modern hominids and that the robusts were primarily herbivores who were hunted to extinction by the graciles. Out of this theory there grew the celebrated popular idea that the ancestral hominids were "bloodthirsty killer apes." But intensive studies of the molar surfaces and patterns of dental wear have failed to demonstrate the existence of dietary specializations associated with the two types.

Until recently it was thought that there was something lacking in the australopithecine bipedal stance, and most textbooks stated that they "could run bipedally but were clumsy bipedal walkers." But analyses of the biomechanical properties of the hip joint have shown that the australopithecines may have been better adapted for bipedalism than modern humans.

This suggests to some experts (Morgan, 1964; James, 1968) that the gracile forms evolved into robusts or other hominids, and that they became extinct, whereas the robusts lingered on until about 750,000 years B.P. at Taung. The most serious drawback of this theory is that Dart's original Taung skull has long been regarded as a gracile type. But since the skull is that of a child, it may have been classified incorrectly (Tobias 1973; Partridge 1973).

The notion that hominids have an innate lust for hunting and killing is often used to explain such activities as hunting for sport, bull-fighting, gladiatorial spectacles, public torture, public execution, and war down through the ages. But none of these activities can be accounted for by invoking innate lusts.