Bradshaw paintings and the Boab: Kimberley rock art linked with a new African tree species found in Australia.

Ben Collins on ABC Australia - Kimberley rock art leads to a new African tree species found in Australia - reports on how a passion for rock art led to the identification of a particular tree in the Kimberley with African 'roots'.

The distinctive boab in Australia and the baobab in Africa and Madagascar are under investigation. There is one species of the Australian boab, six species of the Madagascan baobab, and until recently just one species of the African baobab.

Naturalist Tim Willing has been working in the Broome area of Western Australia, in particular on a recently discovered boab. To perhaps solve this, a connection arose in the form of ancient rock art; Professor Jack Pettigrew, a retired neuroscientist, now spends his time studying the Kimberley rock art - and the boabs.

Pettigrew noticed a distribution correlation between the boab trees and the Bradshaw, or Gwion Gwion, rock art. Both are found only in certain parts of the Kimberley. The Bradshaws are very different to other Australian rock art, with a distinctive style and fine details. Pettigrew wondered about an African influence to the art, where of course the boabs' relative species grow.

The age of the Bradshaws is controversial - some measurements suggest up to 18,000 years old, whilst other theories suggest over 40,000 years ago due to depictions of megafauna. But even the earlier date would be insufficient for the boab to evolve into the modern Australian species.

The flower on the African mountain baobab found growing in Broome. Image: Ben Collins.

To qualify this African connection, Pettigrew attempted to determine the age of the boabs in the Kimberley. By studying particular boab genes, with a predictable rate, Pettigrew calculated that the boab was a much more recent arrival to Australia than previously thought, namely around 70,000 years. This was the connection to the naturalist Tim Willing, with his unidentified boab - a new African species.This brings the age closer to hominid occupation of Australia, and therefore the art. 

Not so, says June Ross, Adjunct Professor of Archaeology at the University of New England, who suggests that we have no evidence for humans being in Australia 70,000 years ago, and there is no evidence of any similar art in Africa anything like that old.

Editor's Note: Genetics now prove that Australia was colonized by anatomically modern humans from 65,000 to 50,000 years ago. The dating of the rock art of the Kimberleys, in particular the Bradshaw or Gwion Gwion paintings, is still controversial and awaits confirmation. However, dates of archaeological occupation and of rock art in northern Australia are being pushed further and further back; Jean-Michel Geneste's archaeological research at the Nawarla Gabarnmang site in Arnhem Land, Northern Territory, has established a date for archaeological occupation of c. 50,000 years and for rock art of 29,000 years. The implications for the Bradshaw paintings are obvious, but clearly further dating must be carried out.