Song of ice and fire: 'Super warming event' may have spurred early human migration out of frozen Africa

PUBLISHED : Wednesday, 22 July, 2015, 7:00am
UPDATED : Wednesday, 22 July, 2015, 3:07pm

A super warming event may have led to our ancient ancestors leaving Africa for the first time around 600,000 years ago, according to a new study by Chinese scientists.

At the time, the earth was a half-thawed snowball, with the southern hemisphere covered by thick ice for almost 100,000 years despite a temperate, warm climate in the north.

The researchers found that this long period of opposing climates coincided with a major episode of early human dispersal from Africa to Europe and Asia.

The study, led by professor Hao Qingzhen with the Chinese Academy of Sciences’ Institute of Geology and Geophysics, was detailed in a paper published in the journal Scientific Reports.

The findings settled a long running dispute between palaeontologists and climate scientists on early human migration.

Homo heidelbergensis, which had a brain as large as modern humans, was believed to have walked out of Africa and populated Eurasia between 600,000 and 300,000 years ago.

Their existence is confirmed by the fossil record and remnants of stone tools found by scientists. DNA analysis also showed them to be the likely ancestor of modern humans.

The timing of major human migration out of Africa has been questioned by researchers studying ancient climates however.

Ice core samples taken in Antarctica showed that there was a major ice age at the time, and the low temperatures and wide-spread glaciers would have confined Homo heidelbergensis to Africa.

Hao’s team studied soil samples buried deep under China’s Loess Plateau and found there was no sign of large scale glaciation in the period, which suggested a “super long” warming period in the northern hemisphere.

Puzzled by the Loess records, the researchers tracked the orbital change of earth’s position around the sun, and found that the southern hemisphere received far less sunlight than the north throughout the period, which led to the completely different climates.

The role of climate in early human migration "has long been a highly contentious issue", the researchers wrote in the paper.

But their findings showed that the northern hemisphere “had been warm enough to maintain hominin occupation” around 500,000 years ago.