Out of Africa: The Origin of Our Species (Part 3)

Australopithecus (robust vs. gracile)

Note: I started reading Africa: A Biography of the Continent by John Reader. The following posts will basically summarize what I find interesting in the book as I’m reading it. None of the ideas or thoughts are of my own.

At about 2.5 million years ago a new heavily built Australopithecus appeared, one that had a much larger body compared to its head size. Its teeth were also correspondingly large, with a chewing surface four to five times the size of the earlier gracile australopithecines, and so they were called “robust” australopithecine or Paranthropus (from Greek παρα, para "beside"; άνθρωπος, ánthropos "human"). Their scull is of heavy and solid appearance, with a broad flat face, solid cheekbones and brow ridges, a low braincase, a prominent crest of bone running from the forehead to the back of the skull, and a massive lower jaw (Figure 1).

Figure 1 - Robust Australopithecus or Paranthropus

Because of Australopithecus robust’s large chewing size, it was unable to apply a great force on any certain point to crack open bones or hard nuts. The purpose was to be capable of prolonged bouts of chewing. So what were they eating that needed to be processed in such large quantities? It must’ve been foodstuff that contained a large proportion of indigestible material.  When their teeth were examined with an electron microscope and compared to those of orangutans (fruit eaters), rhinoceros (grazers), giraffes (browsers), cheetahs (carnivores), and hyenas (scavenger and bone eaters) the greatest similarity was found with the orangutans, indicating that the robust australopithecines had eaten fruit in large quantities just as they were picked up from trees, i.e. including flesh, skin, hard shell, pods, and seeds, which they had to chew into a digestible mass. Their powerful jaw muscles that moved these massive set of teeth separated the robust australopithecines apart from the rest of the hominids, and this specialization served them well for a while. They were able to spread from Ethiopia to South Africa at about 1.6 million years ago. But evolution has taught us that too much of specialization also drives a species into extinction. According to our fossil records, about one million years ago, the robust Australopithecus reached a dead end.

Meanwhile, the gracile Australopithecus also evolved to specialize, but towards an advantage that allowed many of its generations to multiply, and these advantages were tools and intelligence.

To be continued...

Watch: The Ape That Took Over The World (BBC Documentary)