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Rains on the Ga-Mohana hill, in the southern Kalahari, are rare and very seasonal;

the landscape around this rock shelter is semi-arid and the vegetation rare.

However, water was once abundant, as evidenced by tuff formations, a type of rock that forms in the presence of fresh water.

There, a team of scientists has unearthed 22 white calcite crystals, as well as fragments of ostrich eggshell that were used as containers by a group of

Homo sapiens

more than 105,000 years ago.

The journal

Nature

publishes the details on Wednesday.

According to the researchers, this is one of the first concrete evidence of a complex behavior - the accumulation of objects without a practical purpose - in deposits far from the coast.

"We cannot know for sure what the crystals were used for, but we do know that they did not get there by natural processes, that they were not modified, and that tools cannot be made with them, so it

seems that they were collected for their beauty, perhaps , for ritual activities,

"explains Dr. Jayne Wilkins, a researcher at Griffith University in Australia and lead author of the article.

"These crystals tell us that

the inhabitants of the Kalahari 105,000 years ago were already, in many ways, similar to the people of today, with a rich social and spiritual life."

The age of the remains has been determined thanks to optically stimulated luminescence (OSL).

"This is a technique that measures the natural light signals that accumulate over time in sedimentary quartz and feldspar grains," explains Michael Meyer, director of the OSL laboratory at the University of Innsbruck in Austria.

"Each grain is like a miniaturized clock in which we can read this natural light signal (luminescence) that reveals the age of the sediment layers."

Excavation at South Africa's Ga-Mohana Hill North Rockshelter Site Jayne Wilkins

In addition, applying the uranium-thorium method in limestone rock, it is possible to determine and date the presence of water remains in the calcareous tuba formations, which has been located between 110,000 and 100,000 years ago, exactly the same time frame in which there was human presence.

The analysis points to a series of wet periods of green Kalahari throughout history, a situation analogous to that of the Sahara and Arabia.

On the other hand, the research reveals the long cultural history of Ga-Mohana, a place that local communities still use for spiritual activities.

"It's at the edge of the Kuruman Hills and stands out from a largely flat landscape, so it offers expansive views," says Wilkins.

"Today pools of water form between the rocks at the base of the hill after a rain but, in the past, there were also waterfalls that flowed over the edges of the refuge."

Rewriting our origins

According to the authors,

the finding forces us to review some of the theories about the evolution of cultural innovations among the first human populations.

Most of the representative sites of these ancestral communities had been found in coastal regions, such as the famous Blombos cave or that of the Klasies river.

"Our findings show that oversimplified models of the origins of our species are no longer acceptable," says Jayne Wilkins.

"The evidence suggests that many regions of the African continent were involved, the Kalahari was one of many."

In the second half of the last century, technology forced us to rethink some of the explanations about the origins of our species.

New dating techniques, such as OSL, made it possible to date sites more distant in time, exceeding the limits imposed by radiocarbon analysis.

And studies of genetic diversity from mitochondrial DNA pointed to the existence of a last female common ancestor, a mitochondrial Eve, who would have lived in Africa about 200,000 years ago.

The new tests forced to rethink theories such as the so-called Out of Africa, which in its original version held that the ancestors of

Homo sapiens

left the continent before the formation of our species.

Thus, the Out of Africa was then reformulated in a second version to suggest that

sapiens

evolved -at least- 200,000 years ago on the continent, until they became anatomically and culturally modern.

Later, about 50,000 years ago, an evolutionary impulse and a favorable climate would have allowed some of their descendants to leave the continent and spread throughout the world, hybridizing and replacing other species (such as Neanderthals) in Europe and Asia.

African multiregionalism

But new discoveries, such as that of Ga-Mohana, provide additional pieces to complete the reconstruction: the

sapiens

would not have evolved in a single African lineage, but in different populations in different regions of the continent that would maintain intermittent genetic exchanges.

This theory is known as African multiregionalism and maintains that

there was not a single cradle of humanity

, the entire continent would be a mosaic that was shaping the species before spreading throughout the world thanks to that group of explorers that left 50,000 years ago.

One of the objects found at the Jayne Wilkins site

"Part of the problem is that only a few regions have been studied in detail," explains University of Alberta anthropologist Pamela Willoughby in a comment published in

Nature

, "places with natural landscape erosion that have exposed fossils and artifacts of stone".

Deposits in the Rift Valley, in Ethiopia, Kenya and Tanzania, and in the dolomitic limestone caves of South Africa known as the 'Cradle of Humankind'.

But the authors of the new work insist on the need to review the entire continent for evidence of the innovations, going back hundreds of thousands of years.

"Only in this way will we understand the cultural evolution of our most recent common ancestors," they conclude.

According to the criteria of The Trust Project

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