September 29, 2015

The Two Million Year Old Boy from South Africa

New : The Two Million Year Old Boy          [Natgeotv 2011]

A 2 myo clavicle bone belonging to a pre-human boy from a previously unidentified species: Australopithecus sediba.

This was the discovery of the century, finding a new species.

On 15 Aug 2008 Lee Berger and his son were looking for fossils in the World Heritage site 25 miles from Johannesburg. It is known as Cradle of Humankind, because of the pre-human fossils. Many years ago the area was mined by gold prospectors and many caves and rocks were blown up. In a small depression in the Malapa Valley, Lee's son found a hominid clavicle in a rock, and later the lower jaw and a canine tooth. They were from a male child dated 2 myo.

6 myo humans and chimps shared a common ancestor. Australopithecus started walking on 2 legs. But it is not known when Homo appeared as there is a gap in the fossil record, between 2.5 - 1.8 mya. Very few bones of pre-humans have been found, only about 3000.

100s of bone fragments were found in blasted rocks, from animals such as sabre tooth cats, hyena, antelope, mice, rabbits etc. More finds were made, a humerus, scapula and 2 teeth. These were from a second individual. This was an adult female about 30 years of age. Could this be a mother and child? They were 2 hominid pre-humans and named as Australopithecus sediba. They had a mix of modern and old features.

Before this discovery, less than 10 hominid skeletons had been found. The new bones were very different from anything found before. A scan of rocks revealed a skull inside on. This was from an entirely new species as it didn't match anything known.

A lab was set up to make casts of the bones which would be available to researchers all over the world.

Human evolution has not occurred in a straight line as there are many branches and Australopithecus sediba contains old and new features. This new species had an ankle like a human with an ape-like heel bone. It had modern hands with ape-like arms, so could walk upright but still climb trees if necessary. It had a very small brain but it was reshaped to look more human than ape.

It is not known if Australopithecus sediba is a direct ancestor to Homo sapiens.

There was a clue as to how these hominids died - bones from both individuals were unmarked by predators. There were no tooth or impact marks. The bones were well preserved in limestone. Many hominids died violent deaths e.g by animal attacks. So how did these ones die? The boy had 2 broken bones on the forearm so could he have fallen. Today the cave is just a hole in the ground, maybe it was deeper before. Maybe the hominids were searching for water and fell down. Animal bones were also found. There could have been a flash flood which buried all the bones together. But the site was disturbed by the gold miners centuries ago.

Excavation of the site began. The tibia of a 3rd individual was found, a 2nd adult. Then some from an infant about 18 months old. Possibly a family group.


Shown on UK Channel 4 TV in Sept 2015

See also the related programme, FIRST HUMANS: THE CAVE DISCOVERY , on the discovery of
Homo naledi from Rising Star Cave.

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