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A New Look at Some Ancient Fossils Has Just Rewritten Human Evolution’s Story

Similar to humans, technology has undergone changes and advancements throughout its history.

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The positive aspect of science is in its continuous development. The information that was formerly widely known is now being shared as a meme, which is intended to be sarcastic. Diseases that used to cause the death of whole families are now completely eradicated. Additionally, we have repeatedly discovered that our previous understanding of historical events is incorrect.

A new study conducted by academics at the Australian National University in Canberra and the Natural History Museum in London is expected to have a significant impact on our understanding of human evolution.

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And all it took was a second look at some ancient fossils.

The issues with radiometry

There are various techniques to date ancient artifacts – dendrochronology, for example, utilizes the development of trees to work out when locations were active – but one of the more prominent ones is radiocarbon dating. It’s based on nuclear physics, of all things: it dates a site by examining the quantity of carbon-14 left in organic remnants like bones or charcoal.

While creatures are living – everything from a tardigrade to a T. Rex – their tissue absorbs carbon-14 isotopes. Cosmic rays interact with the Earth’s atmosphere, causing them to come at us from many directions, making them impossible to escape.

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It’s only until an organism dies that this absorption ceases – and it’s then that something intriguing starts occurring. Carbon-14 isn’t just any isotope: it’s the only naturally occurring type of carbon that is radioactive, and it has a half-life of roughly 5,730 years. That implies that an artifact from, for instance, ancient Mesopotamia will have around half as many carbon-14 isotopes as it had originally — the remainder will have decomposed into nitrogen. So, by analyzing the ratio of one element to the other, scientists may identify the approximate age of the discovery.

ALSO READ: If you were to fall through a hole in the earth, what would kill you first?

It’s undeniably brilliant, but here’s the problem: far from being the slam-dunk technique, it’s commonly advertised as radiocarbon dating is only efficient on fossils younger than around 50,000 years. That’s why we don’t use it to date dinosaur bones, for instance: to take our old buddy T. Rex, who lived something like 70 million years ago, as an example, the quantity of carbon-14 remaining would be so minuscule as to be impossible to quantify – something like 10-3,678 of the original.

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Even with younger samples, things might go wrong. Homo floresiensis, the so-called “Hobbits” of Flores Island, made headlines in 2004 when it was determined that populations of the hominid had been there as recently as 12,000 years ago – but it turned out to be a mistake. The team which had originally carried out the research had dated the H. floresiensis remains by evaluating the silt in which their bones were located, rather than the bones themselves. That’s generally a totally fine approach – except that the crew didn’t notice the bones lay within an unconformity, making them look younger than they were.

Mix-ups in the timeline

In reality, the Hobbits had lived more than 60,000 years ago — not as thrilling, but it made far more sense historically. There was no longer the conundrum of how H. floresiensis could have thrived alongside H. sapiens – that is, humans – for so long without being bred or battled or driven into extinction. The two species, it transpired, did not really overlap in the area by very much at all.

And a very similar mix-up has been uncovered by the current analyses. Back in 2010, researchers in the Philippines uncovered the bones of what would subsequently be classified as a new archaic human species, Homo luzonensis. As with H. floresiensis, what was striking about the find was exactly how recent it looked to be: early estimations estimated the age of the fossils at around 65,000 years old, during the era when the area was occupied by Homo sapiens.

But again, this has shown to be untrue — and the bones are in reality at least twice as ancient as originally supposed.

A better approach

How do the researchers know? The reanalysis was done using radiometry, but not by detecting carbon-14 levels — instead, the scientists employed a technique known as U-series or uranium-thorium dating. It’s a procedure that’s been in use for half a century already, so you may question why the findings weren’t accurate previously – but the key lies in the unique methods Grün and his colleagues have refined the tech, allowing for pin-pointed precision that was earlier unattainable.

The problem with bone is that it’s an open system,” said Chris Stringer, Research Leader at the Natural History Museum, in a statement. “Uranium can get into the bone, allowing it to be dated, but more can also be added or washed out over time.”

“Previously, you might need to cut a fossil in half and track the uranium through the bone, but this wasn’t feasible on valuable fossils such as the ones we were reanalyzing,” he stated. “Instead, Rainer [Grün, Emeritus Professor at the Australian National University in Canberra] has helped to miniaturize the process, so that tiny samples can be taken using lasers to minimize damage to important areas of the specimen.”

Rectifying history

And the new study has thrown up some very revolutionary results. Take, for example, the two skull pieces, one from a Homo sapiens and the other from a Neanderthal, discovered in the Apidima Cave in Greece in 1978. Originally, radiometric dating turned up some startling statistics, with the Neanderthal skull registering as 40,000 years younger than the Homo sapiens – which appeared odd, given what we know about the two species’ relative places in time.

Instead, experts believed, it was likely two Neanderthal skulls – one of which was a touch strange, yes, but certainly not a Homo sapiens. And as for the dates – well, that couldn’t be true either: not only did Neanderthals come before modern humans, but the figures radiometry was spewing out – something like 210,000 years for the alleged Homo sapiens – were just far too early for H. sapiens to be hanging around in Europe.

But now, with the researchers’ revised methodologies, the mix-up has been unmixed down — and in a potentially surprising way. It appears that the two fossils were initially deposited in two distinct areas, and both dropped into the cave over time. That’s why they were found together despite the 40,000-year age gap – and why the H. sapiens skull fragment, dating from more than 150,000 years earlier than anatomically modern humans were previously thought to have migrated into Europe, is now being celebrated as the oldest fossil of the species ever found in Europe.

“Some of these findings are astonishing,” observed Grün, “but [they] provide an excellent outlook for increasing our understanding of human evolution.”

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I'm Michael, a young enthusiast with an insatiable curiosity for the mysteries of science and technology. As a passionate explorer of knowledge, I envisioned a platform that could not only keep us all informed about the latest breakthroughs but also inspire us to marvel at the wonders that surround us.
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