When the Sahara was the cradle of life
Archaeologists and scientists are reconstructing the history of the Sahara and have discovered that Sahara dried up three million years ago
Samples from the ocean depths containing wind-blown sand indicate when the Sahara desert dried up: three million years ago.
Marine fossils found in Europe and Africa are proof that a huge sea stretched at least half the world and connected Asia to the Atlantic Ocean. This ocean was called the Tethys Ocean and submerged most of the Sahara. Freshwater shells, however, demonstrate that 90 thousand years ago an oscillation of the earth's axis created gigantic lakes and rivers, making the Sahara fertile as happens every 20 thousand years.
- 40 million years ago the Sahara was covered by the ocean.
- 3 million years ago it turned into a desert.
- 90 thousand years ago there was a decisive turning point not only for the Sahara but also for all of humanity.
- Since then it has oscillated between being a green expanse and a desolate land, every 20 thousand years.
The entire African continent is supported by a gigantic piece of earth's crust called a tectonic plate which was in movement 40 million years ago, in the geological era called Eocene. At this point Africa collides with Europe, closing the Tethys Ocean which submerged the entire Sahara. The African plate continues to move so North Africa is pushed up and the Tethys Ocean retreats. Now the entire area of North Africa has emerged, it is dry land.
Wadi While whales are stranded and trapped in ever smaller pools of water turning the Sahara into a desert. Sahara claimed its first victims.
Wadi Al-Hatan is located in the Egyptian Western Desert and precisely in the Fayoum region, about 250 kilometers from Cairo, near Lake Qarun.
Paleontologists are aware of this area as a place where the rarest fossiliferous collections are found, including numerous types of mammals with placenta, several species of fish, reptiles and marine invertebrates. In particular, in the Zeuglodon valley, to the west of the lake, there is the site called the Valley of the Whales where the fossil remains of the genera Basilosaurus, Prozeuglodon and Drudon, extinct ancestors of the current Cetaceans, were found.
In 2005, Wadi Al-Hitan (in english: the Valley of the Whales) was registered in the "Natural Heritage of Humanity" managed by UNESCO. On the UNESCO website ( http://whc.unesco.org/en/list/1186) you can read the reason why this place was included in the prestigious list:
“Wadi Al-Hitan is the most important site in the world regarding the evolution of whales […]. The site has a value that exceeds that of similar sites due to the number, concentration and condition of the fossils, as well as the ease of access and the beauty of the landscape in which it is located….”
The secrets of the Sahara have finally been revealed. Scientists knew the Sahara was forever changing, but now for the first time they have a sense of how quickly it has changed. As soon as the earth's oscillation shifted the rain belt, the return to the desert was rapid and deadly. We saw how the Sahara desert was a very different place from how we know it today. There were lush forests and many animals and plants. Colorful beads made from ostrich eggs, found at an archaeological site in southern Egypt, indicate that 7,000 years ago the Sahara enjoyed its last burst of life before returning to being a desert.
Archaeologists subjected the beads made from ostrich eggs to the carbon 14 test and the result was that they are 7 thousand years old; this means that for 7 thousand years the most implacable desert on earth was home to human, plant and animal life. This suggests that there must have been ostriches once upon a time.
Elsewhere human bones have been found, carefully buried in cemeteries near the lakes. Analysis of these bones reveals that they date back to a period always between 10 thousand and 7 thousand years ago.
Stone tools have been found in archaeological sites not far from the mega lakes and this is certainly the first step in identifying the shores of the ancient lake. At several sites, finely crafted ancient Stone Age tools have been found, suggesting that thousands of years ago on the shores of these lakes man waited for prey and then hunted it. Numerous bone remains of antelopes and other small animals are also found, so when the desert was green it was populated by animals. The remains of these communities suggest that they were not nomadic tribes but that they were sedentary. This is the most sensational demonstration of the desert's latest explosion of green. Striking wall paintings in caves even show men swimming. At several sites across the Sahara Desert, scientists have unearthed similar evidence of life. Remains of elephants, gazelles, hippos and crocodiles, and the rock paintings found give us the idea of a diversified fauna
But not only that, the Italian archaeological mission in Libya has discovered the most ancient traces of milk processing in the remains of a vase from the Neolithic site of Takarkori.
The study of microscopic remains of organic substance preserved on the walls of a vase from Takarkori dated to 5,200 BC, a shelter in the Tadrart Acacus mountains in southern Libya, has provided the first direct evidence of the use and processing of cow's milk.
Already 7,000 years ago, therefore, the Neolithic shepherds who inhabited the Libyan Sahara had reached a high social and economic complexity. Not only did they raise and graze their animals, but as Savino di Lernia, director of the mission and co-author of the study, explains,
“they were fully capable of exploiting all the secondary products of pastoralism. This discovery testifies that there was a stable and advanced breeding system that exploited all animal resources, including milk."
The chemical analyses, conducted by Julie Dunne and Richard Evershed of the University of Bristol, and by Savino di Lernia and Stefano Biagetti, who direct the archaeological mission of the Sapienza University of Rome in Libya, revealed the presence of fats on the ceramic fragments found in Takarkori interpretable with certainty as processed bovine milk. The researchers reached this conclusion thanks to comparison with a reference collection obtained from the milk of current African goats and cattle.
This work thus allows us to establish the oldest African evidence of the use and processing of milk by the Neolithic shepherds of Tadrart Acacus, a use already documented in Saharan rock art which also includes rare milking scenes. Until now, however, the difficulty in dating these pastoral scenes had prevented us from dating with certainty the beginning of milk processing in Africa.
The study is published in the journal Nature.
This gives us an idea of how advanced the Saharan populations were, lulled by a temperate climate with large deposits of fresh water. Scientists knew that giant lakes covered much of the desert but had no evidence that they were connected. The Sahara was covered with forests, lakes and swamps, it was an interconnected system of rivers as NASA radar images suggest, in several of these places numerous freshwater shells are found and this is also a good indication of the presence of an ancient lake.
The mystery is how and when this lush underwater world transformed into the arid desert we see today, and the answer lies not in climate models but in geology.
Five thousand years ago the climatic transition from a Sahara covered in water and rich in vegetation to a much drier Sahara occurred in one or two centuries. This has happened many times throughout its history, regardless of shifting landmasses and astronomical movements.
Now we need to understand what could have dried up the water in the mega lakes
Now scientists are turning to a more recent geological past, the last 10,000 years ago, to find out how quickly this desert may be changing. The question scientists are now asking is: how quickly did the Sahara transform from a bountiful place to a completely barren one?
Under the Sahara, enormous quantities of fresh water are still stored hundreds of meters underground. The Nubian Sandstone Aquifer, located beneath the Eastern Sahara, represents in particular one of the largest underground water reserves on the planet: it extends under a region more than 2 million square kilometers wide, in the subsoil of Libya and Egypt, at a depth that varies between 500 and 3500 meters, and contains approximately 150 thousand km3 of water! As we have seen, between 5,000 and 10,000 years ago the Sahara was certainly a lush region, more humid, with intense summer rains and over which an endless savannah extended which gave hospitality to antelopes, lions and also very socially advanced human settlements.
Where did the clouds and rain go then? They migrated elsewhere because of the earth's axis! And with them the men also decided to abandon those lands which were consequently becoming more and more inhospitable.
The inclination of the rotation axis in fact varies cyclically over thousands of years: when the Earth is more inclined with respect to the rotation plane, the difference between winter and summer increases, while when our Planet is less inclined the contrast also decreases between the cold and hot seasons.
Well, 10,000 years ago the inclination of the earth's axis was such that the Sahara received approximately 8% more solar radiation during the summer and 8% less in the winter than today, so in North Africa the summer was hotter and the winter colder than they are today. However, the contrast between very hot summer seasons and rather cool winters gave rise to a monsoon circulation that was much more intense than today's, and the African summer monsoons were able to bring clouds and abundant rainfall right into the heart of the Sahara, where the very winters dry were then followed by very hot but also rainy summers.
What happened to those people? Some remained, becoming nomads or semi-nomads, the famous Tuareg. But everyone else emigrated to the Nile Valley.
In the future the Sahara will once again transform into a verdant paradise of thousands of kilometers. In the reborn paradise, men and animals will once again be cradled as in lost times.
