What happened 900,000 years ago?

According to the results of a genomic study published last year, At one point in history, the ancestors of modern humanity dwindled to a population of just 1,300 people.. This situation has brought us to the brink of extinction in the region called “bottleneck”, as scientists call it. New research has revealed that there was also a massive human migration from Africa.

The discovery confirms the earlier date of population decline and shows that the two events are linked by a common denominator; this event is known as the Middle Pleistocene transition; During this event, Earth’s climate experienced a period of extreme turmoil that led to the extinction of many biological species. species.

The movement of early humans from Africa to Europe and Asia is difficult to reconstruct. The best evidence we have consists of a small number of bone remains and mostly stone artefacts, which can be difficult to evaluate today. But the data shows that This was not a single incident; were various waves of early hominids and ancestors of modern humansThose who pack their belongings and make long journeys to new environments.

Two recent studies attributed the migration of people to the same “bottleneck” in population, that is, a critical decline in their numbers. A careful study of the human genome showed that the “bottleneck” in the population resulted in a loss of nearly 100% of genetic diversity. 900,000 years ago. A second study, published a few weeks later, examined early archaeological finds from Eurasia and determined the date of the “bottleneck.” 1.1 million years ago.

This discrepancy makes it difficult to pinpoint the climatic event that could have caused or at least contributed to the decline, so geologists Giovanni Muttoni of the University of Milan and Dennis Kent of Columbia University made an attempt to narrow down the time frame of the decline. bottleneck.

First, the researchers reevaluated records of early hominid habitats in Eurasia and found a number of sites reliably dated to 900,000 years ago. In contrast, the dating of older finds used as evidence of population bottlenecks was more uncertain and therefore controversial.

They compared their findings Data on marine sediments preserving evidence of climate change in the form of oxygen isotopes. The proportion of oxygen trapped in sedimentary rock layers indicates whether the climate was warmer or colder when minerals were precipitated.

Genomic data and dating of hominid finds indicate that the bottleneck and migration occurred simultaneously. During a transition period in the mid-Pleistocene, global ocean levels fell and Africa and Asia dried out, creating large areas of arid climate. Hominids living in Africa found themselves in terrible conditions, deprived of food and water. Fortunately, as sea levels fell, land routes to Eurasia opened and they were able to move there. This was their salvation and therefore our salvation.

They note that this does not mean that hominids did not migrate before. Most likely, the “bottleneck” in the population of the ancestor of modern Homo sapiens and its migration occurred simultaneously as a result of climatic upheavals that occurred approximately 900,000 years ago.

We hypothesize that increased aridity during Marine Isotope Phase 22, which caused savannas and arid regions to spread across much of the African continent, drove early Homo populations in Africa to adapt or migrate to avoid extinction.
– researchers write in their study.

Rapid migration and associated escape routes in response to a severe climate trigger may explain migration out of Africa 0.9 million years ago and add to existing genomic evidence in modern African bottleneck populations.