There is an area in Africa that is commonly called the cradle of humankind because it has long been believed that this is where human ancestors first evolved. The reason for this belief was based in large part on the fact that there have been so many human fossils found in the region.

Located between Kenya and Ethiopia, the area is filled with human fossils as well as many other artifacts that have been dug up over the years.

Many palaeoanthropologists argue that this may not actually be where humankind got its start. Instead, they suggest, it began further down near the southern tip of Africa. East Africa is thought to be the source of humanity because of all these fossils.

If this is correct, there needs to be a reason why nearly a third of all ancient hominin fossils in Africa come from this region. A new study published in Nature Communications may have done just that.

The researchers argue that the reason there are so many fossils here is that this is the location of the Turkana Rift, which is a path along which a continental split is occurring and has been for millions of years.

The tectonic plates deep underground are always moving, but at a very slow pace. This movement sometimes causes entire continents to split apart or come together over the course of time. This is a well-documented phenomenon.

When a container gets pulled apart, the land gets slowly thinner and thinner as it is stretched out over the course of millennia. As the land is stretched out, it pushes material that was once buried deep up closer to the surface.

Columbia University PhD student Christian Rowan is the lead author of the study. He explains in the study:

“The thinner the crust gets, the weaker it becomes, which helps promote continued rifting.”

Estimates say that the Turkana Rift began separating 45 million years ago, and a process known as necking, which is when the crust is stretched and thinned, began just 4 million years ago.

This timeline matches up nicely with when humans would have been living and spreading into this region.

Today, the area where this rift is occurring is approximately 13 kilometers (8 miles) thick, which is quite thin compared to the 35 kilometers (21 miles) thick on either side.

This dramatic reduction in the thickness of the ground in this area has made it much easier for archaeologists to find fossils. If the same thing occurred in other parts of Africa, they argue that the number of fossils there in those locations would go up dramatically as well.

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