Out of Africa

A new fossil find in Morocco is overturning many notions in human evolution. The new finds are believed to be 300,000 years old. This is about 100,000 years older than modern man (Homo Sapiens) was previously thought to have evolved and in a completely different part of Africa.

morocco.jpg

Map of Africa showing Morocco

The fossils show a face that is like that of a modern human but with a more elongated skull. This has led people to wonder if the rounded skull is a more recent evolutionary change. The fossils were accompanied by other finds at the same level which give us insight into the lives of these primitive humans. Excavations show traces of fire, wood handled spears and also flint tools. It was using these flint tools that the skulls were dated using thermoluminiscence.

Thermoluminiscence is a property of some crystals which absorb electromagnetic energy over a long period of time. When these crystals are heated, this radiation is re-emitted in the form of light. Things that have been buried in the soil receive energy from radioactive elements in the soil and cosmic rays. So things that have been buried longer would have absorbed more energy and will glow brighter when heated,

220px-Thermolumine

Thermoluminiscence in fluorite

Before this, the oldest found remains of our species had been in Ethiopia. Separate excavations revealed skulls that were 160,000 and 195,000 years old in Herto and Omo-Kibish both of which are in Ethiopia. This led to the belief that modern humans evolved in East Africa before spreading throughout the African continent and eventually beyond.

thiopia

Map of Africa showing Ethiopia

This idea now has to be changed as human evolution seems to have involved populations throughout Africa. But beyond Africa, there is remarkable homogeneity.

Multiple genetic studies have shown that practically all people outside Africa are descended from a very small genetic pool probably from a single group of humans who migrated out of Africa some 70,000 to 50,000 years ago.

There is one exception thought, in Papua New Guinea, a genetic study found the natives having 98% DNA from this migration but the remaining 2% from a much older migration possibly as long ago as 140,000 years. In other parts of the world, the descendents of this earlier migrations seem to have largely vanished. We know them through their tools in Saudi Arabia and India dated 100,000 years old and their skeletons in Israel which are believed to be between 120,000 to 90,000 years old.

Today, there remains more human genetic diversity within Africa than the rest of the world.

References

https://www.nytimes.com/2017/06/07/science/human-fossils-morocco.html?_r=0

https://www.nytimes.com/2016/09/22/science/ancient-dna-human-history.html

https://en.wikipedia.org/wiki/Thermoluminescence

 

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