Question

C) What do the Skhul fossil suggest about the emergence and dispersal of Homo sapiens? Did H. sapiensemerge in Africa and successfully migrate out of Africa in one wave? Or were there waves of unsuccessful migrations during the evolution of our species?

Answer 1

The oldest known Homo sapiens fossils outside of Africa come from caves in Israel - Misliya (about 180,000 years old), Skhul (about 90,000 years old) and Qafzeh (about 120,000 years old).

These probably represent populations that intermittently occupied the region and it is unlikely that there was direct evolutionary continuity between the Misliya and later Skhul/Qafzeh peoples.

Evidence shows that the first wave of humans to move out of Africa did not have too much success on their travels. At times it appears they were on the brink of extinction, dwindling to as few as 10,000. The eruption of a super volcano, Mount Toba, in Sumatra 70,000 years ago may have led to a 'nuclear winter', followed by a 1,000-year ice age. This sort of event would have put immense pressure on humans. It may be that humans were only able to survive these extreme conditions through cooperating with each other. This may have led to the formation of close family groups or tribes and the development of some of the modern human behaviours we are familiar with today, such as cooperation.

Between 80,000 and 50,000 years ago another wave of humans migrated out of Africa. These humans are likely to have been ‘modern’ in terms of their appearance and behaviour. Due to their newly cooperative behaviour they were more successful at surviving and covered the whole world in a relatively short period of time. As they migrated they would have encountered earlier, primitive humans, eventually replacing them.

Genetically, the six billion people of today’s world vary very little from these earlier Homo sapiens that ventured out of Africa. Homo ergaster (or African Homo erectus) may have been the first human species to leave Africa.

Fossil remains show this species had expanded its range into southern Eurasia by 1.75 million years ago. Their descendants, Asian Homo erectus, then spread eastward and were established in South East Asia by at least 1.6 million years ago.

Early dispersals into Eurasia were more expansive than previously thought. And it was thought that early dispersals into Eurasia were unsuccessful and remained restricted to the Mediterranean forests of the Levant, on the doorstep of Africa.