The confirmation bias refers to a psychological tendency of people to ignore any facts that undermine preconceived notions of the world. Perhaps a good example of the bias at work is the manner that Australian prehistory has largely been ignored because it throws up countless mysteries that are inconsistent with traditional theories about Australian and world evolution.
Mungo Man is one spanner in the works of the traditional theories. Mungo Man was a hominin with a fine skeleton like modern humans who was estimated to have died 62,000 years ago. The ANU's John Curtin School of Medical Research found that Mungo Man's skeleton's contained a small section of mitochondrial DNA. After analysing the DNA, the school found that Mungo Man's DNA bore no similarity to the other ancient skeletons, modern Aborigines and modern Europeans. Furthermore, his mitochondrial DNA had become extinct. The results called into question the 'Out of Africa' theory of human evolution. If Mungo Man was descended from a person who had left Africa in the past 200,000 years, then his mitochondrial DNA should have looked like all of the other samples.
Another spanner in the traditional theories were the Kow Swamp skeletons from northern Victoria, which were reminiscent of Homo erectus. Specifically, they had thick brow ridges, sloping foreheads and very large teeth. If the Kow Swamp skeletons had been found in Indonesia and dated at 100,000 + years, then they might have been categorised as Homo erectus but being found in Australia and dated at only 10,000 years was problematic. According to traditional theories, Homo erectus never reached Australia and was believed to have died out when Homo sapiens reached Indonesia in excess of 50,000 years ago. Even if the Kow Swamp people weren't Homo erectus, it was hard to explain why an ancient looking people occupied Australia after a more modern looking people had been in Australia.
While Mungo Man and the Kow Swamp skeletons undermine theories of the biological evolution of humanity, the Bradshaw Paintings (Gwion Gwion) undermine theories of cultural evolution. A fossilised wasp nest covering one of the paintings has been dated at 17,000 + years old, which is highly problematic because the art is unlike palaeolithic art found elsewhere in the world. Specifically, paleolithic art typically uses animals as the primary subject while the Bradshaws typically depict humans. In addition, the Bradshaws show the humans with tassels, hair adornments, and possibly clothing. Such body adornments are usually found in agricultural societies that have developed hierarchical systems of status. In a nutshell, the art shows cultural approaches that were not believed to exist until agriculture developed around 10,000 years ago.
Aside from being problematic because of the signs of an agricultural culture 10,000 years before agriculture developed anywhere in the world (and on a continent where agiculture was not believed to have developed until the arrival of Europeans), the art is problematic because of some of the technology and animals portrayed. For example, one cave painting shows a line of deer, which is surprising considering there is no evidence of deer ever existing in Australia prior to the arrival of Europeans. Another painting of a boat seems to show a rudder, a keel and a design typically fashioned using metal tools; however, at 17,000+ years old, such a boat would predate the development of such technology by 15,000 years.
The prevalence of migrant flora and fauna that arrived prior to Europeans also undermines conceptions that Australia fauna and flora owed their uniqueness to geographic isolation. The migrant flora includes the boab tree and kangaroo grass, which are native to Africa. The migrant fauna includes the keelback snake, bogal, water rat and dingo that had ancestral origins in Asia. The lengthy flow of flora and fauna back and forth between Australia and other countries pose some questions about why some species took hold but some did not. For example, if humans brought dogs with them in their canoes from India, why didn't they bring pigs when walking overland from Papua New Guinea? Likewise, if the boab tree and kangaroo grass could reach Australia from Africa, why couldn't rice reach Australia from Asia or sweet potatoe from Papua New Guinea?
For those people who seek the certainty of agreement, the mysteries of Australian prehistory are highly threatening because they undermine what they have been taught and any possible answers they develop are unlikely to unite audiences in consensus. For those driven by curiosity; however, the mysteries of Australian prehistory provide countless opportunities to see the world anew.