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Modelling the Peopling of Australia

5 February 2023
Ancient history, Archaeology

At https://phys.org/news/2023-02-remapping-superhighways-australians-reveals-year.html … sophisticated models combine with recent improvements in demography and wayfinding based on geographic inferences, show the scale of the challenge faced by the ancestors of the Aborigines. Models seem to dominate a lot of modern research. They assume the occupation of Australia took place around 60,000 years – or somewhere between 75,000 and 50,000 years ago. The dates tie in with the Out of Africa theory. They also claim the colonising movement began via the island of Timor, although accept there was later migration from New Guinea. The model shows a rapid expansion southward into the southern and SE zone, but a fairly late arrival in Tasmania. Questions remain – see https://doi.org/10.1016/j.quascirev.2023.107971

Over at https://phys.org/news/2023-02-world-oldest-fossils-oily-gunk.html … we stay in Australia. At the Pilbara region of Western Australia there is a remarkable piece of earth’s crust, thought to be one of the most ancient sections of geology preserved over 3 billion years ago – more or less unchanged. West of the town of Marble Bar are black rocks composed of find ground quartz, known as chert. It was said to contain the fossilised remains of microbes. These are very much like bacteria that are alive and kicking in the modern world – but this is now disputed. In Science Advances, the new study shows certain rich compounds found in the chert were produced by non-biological processes. This implies the fossil bacteria are not the remains of early life forms but, instead, artifacts of chemical and geological processes.

In 1993, the discovery of these outcrops, dated over 3 billion years ago, led to the interpretation of them as the charred remains of  fossilised bacteria, cyanobacteria. These are thought to be the earth’s first oxygen producing organisms. This implied life was already pumping oxygen into the air a billion years before earth’s atmosphere is thought to have become rich in oxygen. Obviously, that was bound to provoke a response from other scientists keen to keep to the status quo, as is their want. The finding was seriously challenged in 2002. A team led by Martin Brasier said the so called fossils displayed a variety of shapes and size uncharacteristic of cyanobacteria – even though the original claim was that they were charred. They were, it is said, inconsistent with microbial life. In addition, Brasier and team said the chert beds were not horizontal, or laid down on the sea floor, but angled veins across underlying layers of rock. It was a carefully crafted piece of geological investigation which went on to say the cherts must have formed at high temperatures during volcanic activity – an environment hostile to life. In other words, the so called fossils were formed from graphite impurities. Brasier toyed with the idea the carbon associated with the fossils may not have had a biological origin. The new study took a closer look at the black chert veins using a high magnification electron microscope. They discovered an oil like substance in residence – in fractures and as petrified droplets. They were found with hot fluids rich in silica and carbon that had trickled through cracks in lava flow below vents in the sea floor – vents similar to modern black smokers. Here we are at the root of the issue. We are back on the sea floor – but at a vent location.

The discovery poses another question. Organic compounds such as oil and gase, known as fossil fuels, are thought to form from the dead remains of algae, bacteria, and plants, generated when they are buried and heated to high temperatures. Chemical reaction reduce organic compounds which accumulat to form oil and gas fields, which are usually dated much later than 3 billion years ago. The black chert, on the other hand, make scientists now wonder how organic compounds could form enmesshed between thick layers of lava. One explanation may be, non-biological processes? Hence, we have a situation that is far from over and possibly also contrary to mainstream thinking.

We may even wonder if scientists have an adequate explanation for the origin of oxygen as recent research has shown it could have been around at planet formation. In that situation oxygen would have been integral to earth and may have seeped out at the seafloor vents. Another consensus theory that may be up for grabs.

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