Humans were reduced to mere 1,300 people some 900,000 years ago due to climate change

Ancestors of modern humanity faced a dire predicament around 900,000 years ago, teetering on the brink of extinction, with their numbers dwindling to a mere 1,300 individuals owing to climatic shifts.

As detailed in a study published in the Proceedings of the National Academy of Sciences, the decline in population and widespread migration of humans out of Africa can be attributed to a pivotal event known as the Mid-Pleistocene Transition, during which Earth’s climate underwent significant upheaval, leading to the demise of numerous species.

Reconstructing the movement of early humans from Africa into Europe and Asia is a challenging endeavor. The available evidence, comprising fossils and stone tools, suggests that this migration occurred through multiple waves rather than a singular event.

Recent research endeavors have shed light on the population bottleneck resulting from human migration through various analytical approaches. One study examined early archaeological sites in Eurasia, dating the bottleneck to 1.1 million years ago, while another conducted a detailed analysis of the human genome, pinpointing a population bottleneck approximately 900,000 years ago.

Geologists Giovanni Muttoni of the University of Milan and Dennis Kent of Columbia University sought to refine the timing of this bottleneck. They re-examined records of early hominid habitation sites across Eurasia, identifying a cluster of sites reliably dated to 900,000 years ago. The convergence of genomic data and dating of hominid sites suggested that the population bottleneck and migration occurred concurrently.

During the mid-Pleistocene transition, global ocean levels receded, leading to arid conditions in Africa and Asia. However, the diminished sea levels created land routes in Eurasia, facilitating migration. The researchers propose that the adverse climatic conditions in Africa prompted early Homo populations to adapt or migrate to evade extinction.

The researchers posit that a rapid response to severe climatic conditions, coupled with the means to escape, drove the migration out of Africa approximately 0.9 million years ago, contributing to the genomic evidence of a bottleneck in modern African populations.