Great Rifte Valley
How did humans become humans? Understanding when, where and under what environmental conditions our ancestors lived is fundamental to solve the riddle of human evolution.
Unfortunately, establishing a timeline of initial human evolution has been difficult for a long time – but the Ancient volcanic eruptions in East Africa They can be the key.
A new one, published in the Proceedings of National Academy of Sciences, refines what we know about the volcanic ash layers in the Turkana Basin in Kenya. This place produced many fossils of primitive humans.
Research provides high precision age estimates, taking a small step towards establishing a more refined schedule of human evolution.
Millions of years of volcanic eruptions
O Great Rift Valleyin eastern Africa, it houses several sites of world -renowned fossils. Of these, the Turkana Basin is undoubtedly the most important region for research on primitive human origins.
This region is also within a active limit of tectonic plates – A continental slit – which triggered volcanic eruptions over millions of years.
As the early humans and their hominid ancestors walked through these landscapes of the Rift Valley, volcanic eruptions often covered the earth with ash particles, Sottering your remains.
Over time, many fossil layers were interspersed between layers of volcanic ash. For current archaeologists, these Layers are pricelessas markers of geological time, sometimes in vast regions.
Excellent time markers
Volcanic eruptions are excellent temporal markers because they occur very quickly, geologically speaking. As hot magma erupts, it cools and solidifies in particles of volcanic ash and pumonal rocks.
The pomes stone often contains crystals (minerals called feldspatos) that function as natural “chronometers”. These crystals can be dated directly through radiometric dating.
By dating the layers of ashes that are directly above and below the fossil findings, we can establish the age of the fossils themselves.
Even in the absence of these minerals, the layers of volcanic ash can also help in dating archaeological sites. This is because the gray particles of different eruptions have unique chemical signatures.
This distinct geochemistry “fingerprint” means that we can track a specific eruption at great distances. We can then assign an age to the layer of ashes, even without dauntable crystals.
For example, a layer of ashes in Ethiopia, or even at the bottom of the ocean, can be compared to one in Kenya. Provided that their chemical compositions correspond, We know they came from the same eruption at the same geological point in time. This approach has been applied in the region for many decades.
Previous reference studies have already established the geology of the Turkana Basin.
However, frequent eruptions in the region often have only a few thousand years apart. This makes many layers of ash essentially indistinguishable in time. In addition, some layers of ash have very similar “fingerprints”, being difficult to differentiate them safely.
These challenges made Nariokotome tufts difficult, three layers of volcanic ash in the Turkana Basin. Although the rocky record clearly indicates that they are three layers of distinct ashes, their age estimates and chemical signatures are very similar. Scientists sought to reduce them.
What did you find?
Compared to previous methods, modern dating tools can achieve an accuracy of a higher order of quantity.
In other words, we can now safely distinguish layers of volcanic ash that erupted with Only 1000 to 2000 years of difference. Applying this method of high precision to Nariokotome tufos, the issue was resolved as three distinct volcanic events, each with a precise eruption date.
However, the determination of ages is not sufficient to completely distinguish these volcanic layers. As the gray layers have formed so close in time – and potentially very similar volcanoes – they also have geochemical “fingerprints” of remarkably similar main elements. The larger elements are the most abundant in rocks, but they cannot always tell us a lot about the age and origin of the rocky material.
That’s where the oligoelements prove especially useful. These are elements that occur in very small amounts in the rocks, but provide much more distinct chemical signatures.
Using laser mass spectrometry, they analyzed the composition in trace elements of both ash particles and associated pumon stones. This provided unique fingerprints of trace elements for each layer – still similar but distinct.
Retrace human history
After obtaining accurate age estimates and distinct geochemical profiles, scientists traced these ashes layers in important archaeological sites.
For example, the West Turkana Nadung’a site, which is thought to be a prehistoric slaughter site, has produced about 7000 stone tools. Updated age estimates now make this site approximately 30 000 years older than previously thought.
Most importantly, they showed that these refined methods can be applied beyond Kenya. Traced the layers of ashes of equivalent ages, from Kenya to the Konso formation in Ethiopia, indicating that they came from Three Individual Eruptionss, in which the material was spread over great distances.
Nariokotome tufts are an important study case that demonstrates the powerful combination of high precision dating with detailed geochemical fingerprints. As these techniques are applied to more layers of ashes, both in the Turkana Basin and potentially beyond Kenya, we will have a better understanding of Key issues in human evolution.
Did new technologies and tool species gradually or suddenly emerge? Has there been more than a kind of hominity simultaneously? How did climate change, climate and frequent volcanism affect initial human evolution?
Now that we have precise geological lines of time for the places where these artifacts were found, we are a step closer to answer these longtime questions About primitive humanity.
