Australopithecus africanus

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Austalopithecus africanus is an extinct species of hominid of the genus Australopithecus.

Raymond Dart found a natural endocast of a higher primate from the quarry at Taung in the year 1924. Dart spent several months with a chisel removing the limestone matrix around the "Taung child." Dart found it improbable that an ape would live in such a dry region as that part of South Africa. Dart also noticed that the permanant molars were broad and large, that the milk canines were very small, and that the forehead does not recede as much as in the apes. Most importantly, the foramen magnum is further forward in this skull than it is in today's great apes, which shows that the head was balanced above the spine. This means that the Taung child was bipedal with an erect posture. Dart placed the new find in the category Australopithecus africanus in an article published in Nature on February 7, 1925. But many scientists of the time considered the specimen to be an aberrant form of ape because they assumed that the origin of mankind lay in Asia or Europe. (Jurmain et al., Introduction to Physical Anthropology 2000:276-277)

Robert Broom made further discoveries in South Africa at the sites of Sterkfontein, Kromdraai, and Swartkrans. Dart himself began excavating again at Makapansgat in 1947. Over thirty specimens of hominids had been found at these sites by 1949. Ron Clark found a nearly complete skeleton of an australopithecine at Sterkfontein in 1998, which is estimated to be 3.6 to 2.5 million years ago. (Jurmain et al., Introduction to Physical Anthropology 2000:278)

D. L. France writes about the species: "They have a projecting face and some post-orbital constriction. Also, they have canines that do not project much beyond the tooth row, and they have no diastema. The teeth exhibit thick enamel, though they have relatively parallel tooth rows. Postcranially, they have relatively long arms, but they have the modifications in the spinal column and lower limb bones that suggest bipedalism." (Physical Anthropology 2004:164)

But the brain is relatively small at around 405 cm³, with an estimate of 440 cm³ for adults. Gorillas, for example, have an average brain size that is about ten percent greater. But the comparison should be made to a primate of comparable weight such as the bonobo, which averages 356 cm³ for the male and 329 cm³ for the female. This means that the Taung child would come to have a brain around 25% greater in size. (Jurmain et al., Introduction to Physical Anthropology 2000:277) This shows that not all traits of modern humans were derived at the same time, as changes in locomotion and dentition are found in Australopithecus africanus without a great difference in cranial capacity.

Acknowledgments

• PeterKirby 18:10, 27 Apr 2004 (BST)