Question

Describe briefly the anatomical, cultural and environmental reasons that allowed Homo erectus to be the first human/hominid to leave Africa nearly 2mya?

Answer 1

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 descendents, Asian Homo erectus, then spread eastward and were established in South East Asia by at least 1.6 million years ago.

However, an alternate theory proposes that hominins migrated out of Africa before Homo ergaster evolved, possibly about 2 million years ago, prior to the earliest dates of Homo erectus in Asia. These hominins may have been either australopithicines or, more likely, an unknown species of Homo, similar in appearance to Homo habilis. In this theory, the population found at Dmanisi represent a missing link in the evolution of Homo erectus/Homo ergaster. Perhaps too, the evolution of Homo ergaster occurred outside of Africa and there was considerable gene flow between African and Eurasian populations.

This theory has gained more support in recent years due to DNA research. Evidence from a genetic study indicates an expansion out of Africa about 1.9 million years ago and gene flow occurring between Asian and African populations by 1.5 million years ago. More physical evidence is needed from key areas in Eurasia such as Iran, Afghanistan and Pakistan, but politics is currently making this difficult.

While there is some debate about whether Homo ergaster was the first of our ancestors to leave Africa, they did possess the physical and cultural attributes that would have aided dispersal through the arid environments of northern Africa and the Middle East. These attributes included:

• a modern body shape with an efficient striding gait suited to travelling over long distances, although smaller statures are represented in the remains from Dmanisi
• a sufficiently developed intelligence to cope with unfamiliar environments, although did not require a brain size much bigger than Homo habilis, with an average brain size of 610cc
• improved technology to aid subsistence (Oldowan-style tools or Mode1 Technology have been found at sites in Dmanisi, Georgia, and northern China, both dating to 1.7 million years old)
• a diet that included more meat and which increased the food supply options in seasonally arid environments