Australopithecus sediba

• Australopithecus sediba are the human-like creatures, whose fossils were first found in South Africa, in Malapa in the famous Cradle of Humankind World Heritage Site, in 2008 and were first described in 2010.

The team which discovered the remains has recently come with deeper analysis of the remains and says that they are the ancient ancestors of modern humans and are dubbed as missing link between apes and humans.

As per the scientists, the features seen in the brain, feet, hands and pelvis of A. sediba all suggest this species was on the direct evolutionary line to us – Homo sapiens. This is a big claim and, if correct, would sideline other candidates in the fossil record for which similar assertions have been made in the past.

Age of Australopithecus sediba

• Whereas original estimates had put the age of the remains at somewhere between 1.78 and 1.95 million years old, the new analysis has narrowed this window of uncertainty to just 3,000 years. The new age is now between 1.977 and 1.98 million years old.
• This is the time in human evolution which should be seeing the beginnings of our genus, Homo. Until now, fossils dated to 1.9 million years ago — and mostly attributed to Homo habilis and Homo rudolfensis — have been considered ancestral to Homo erectus, the earliest undisputed human ancestor.
• Au. sediba hit headlines last year after a scientist’s nineyear-old son found the partial skeleton of a 60-pound 10 to 13-year-old male at a site Malapa.

Brain of Australopithecus sediba

• As per the high-resolution X-ray scan of the male specimen’s skull, A. sediba‘s brain to have been about 440 cubic centimetres in volume, or about the size of a medium grapefruit.
• This is smaller than much older fossils in the record such as the famous “Lucy” specimen, Australopithecus afarensis (3.2 million years), but, intriguingly, the shape is more human-like, especially at the front. This may hint at the start of the re-organisation of the brain that would be necessary to make us what we are today.

Pelvis:

• The Pelvis of Australopithecus sediba is short and broad like a human pelvis.
• It has been theoretically hypothesized that modern human pelvis evolved in tandem with the gradual growth in brain volume – facilitating the birth of babies with bigger heads.
• But, A. sediba gives the lie to this theory because it had a modern-looking pelvis while possessing a small brain.

Hands:

• The hands look far more like a modern human hand than an ape hand. Its fingers are shorter relative to the thumb than in a chimpanzee.
• And yet, it appears to have possessed powerful muscles for grasping, suggesting A. sediba spent a lot of time clambering through the branches of trees.
• The team also argues that the dexterity would have been there to make simple tools.

Foot:

• The ankle joint is mostly human-like in form and there is some evidence for a human-like arch and Achilles tendon.
• But A. sediba possessed an ape-like heel and lower tibia, or shin bone.
• The scientists think this combination may have led to a distinctive type of walk when the creature was not climbing in trees. (with inputs from BBC Science News)
  

Note: Ardy and Lucy:

Fossils of A. ramidus or Ardy were first found in Ethiopia in 1992, but it took 17 years to assess their significance. Ardi is a more primitive hominid than Australopithecine skeleton, Lucy. Researchers describe this 4.4 million-year-old ancient human creature – nicknamed “Ardi” – that also may be a direct ancestor to us. The 17-year investigation of the fossils is named as Science journal’s big breakthrough of 2009.