Ancient humans may have paused in Arabia for 30,000 years

According to the consensus among most scientists, the origin of modern humans can be traced back to Africa over 200,000 years ago. A significant migration event took place between approximately 60,000 and 50,000 years ago, during which humans dispersed across various parts of the world.

However, recent research published in the Proceedings of the National Academies of Sciences has shed light on previously unknown aspects of human migration. This study has uncovered numerous distinctive genetic changes in the human genome, revealing a new chapter in our understanding of human history.

The findings suggest the existence of an extended period of human settlement known as the “Arabian standstill,” lasting up to 30,000 years. During this time, humans inhabited and adapted to the colder climate of the Arabian Peninsula before eventually venturing into Eurasia and other regions.

The genetic adaptations that occurred during this Arabian standstill still have implications today. Under present-day conditions, many of these genetic changes have been linked to various diseases, including obesity, diabetes, and cardiovascular disorders.

History in our genomes

Since the publication of the first human genome in 2000, the amount of available human genomic data has grown exponentially. These vast datasets hold valuable information about significant events in human history. Scientists have been actively developing novel techniques to uncover traces of these events.

As our ancestors ventured out of Africa and migrated to different parts of the world, they encountered new environments and encountered various challenges. These novel pressures would have triggered adaptations and genetic changes in their populations. These genetic changes would then have been inherited by modern humans.

Previous studies based on genomic data have provided insights into the timing of human migration out of Africa, suggesting it occurred between 60,000 and 50,000 years ago. However, our understanding of the specific genetic adaptations that took place during this critical period remains limited.

Despite the wealth of genomic data available, there is still much to learn about the genetic changes that occurred when ancient humans left Africa and dispersed across the globe. Ongoing research aims to address this knowledge gap and uncover further details about the genetic adaptations that shaped the course of human history.

Ancient adaptation events

Our team of researchers specializing in evolution and medicine has made significant discoveries regarding the genetic aspects of the ancient human diaspora. Through the examination of both ancient and modern genomes, we have uncovered evidence suggesting that genetic selection played a crucial role in facilitating this widespread migration of early humans.

By analyzing ancient human genomes, we have been able to identify instances in which specific genetic variants were strongly favored and rapidly spread throughout populations in what is known as a “hard sweep” event. Interestingly, such events are relatively rare in modern human genomes, likely due to subsequent intermingling between populations, which has obscured or modified the traces of these genetic changes.

In previous research, we pinpointed 57 regions within the human genome where a beneficial genetic variant, initially rare, effectively replaced an older variant in ancient Eurasian populations.

In our latest study, we focused on reconstructing the historical dispersion of these genetic variants and estimating the temporal and geographical origins of the selection pressures that drove their spread. Additionally, we identified the specific genes within each region that were likely the target of selection. This knowledge has provided valuable insights into the ancient pressures that potentially contributed to the selection of these genes.

By combining our findings from ancient and modern genomic data, we have enhanced our understanding of the genetic dynamics during the period of the human diaspora, shedding new light on the forces that shaped our ancient ancestors’ genetic makeup.

Coping with cold

Our research reveals that early humans experienced a prolonged period of adaptation lasting approximately 30,000 years before the major diaspora that occurred between 60,000 and 50,000 years ago. We refer to this phase as the “Arabian standstill,” which is supported by genetic, archaeological, and climatic evidence indicating that these ancient humans predominantly inhabited the Arabian Peninsula and its surrounding regions.

During this period, significant genetic adaptations took place, particularly in regions of the genome associated with fat storage, nerve development, skin physiology, and the presence of cilia, tiny hair-like structures in our airways. Remarkably, these genetic changes bear functional resemblances to adaptations found in present-day Arctic-dwelling humans and other mammals.

Additionally, we observed functional similarities between these genetic adaptations and previously identified human adaptive genes originating from interbreeding events with Neanderthals and Denisovans, distant relatives of humans who also adapted to cold Eurasian climates.

The overall patterns indicate that the genetic changes were likely driven by the necessity to adapt to the cool and arid climates prevalent in and around prehistoric Arabia between 80,000 and 50,000 years ago. These adaptations would have prepared early humans for the subsequent encounters with cold Eurasian climates they would face during their dispersal.

Old adaptations, modern diseases

The genetic adaptations that occurred during the expansion of humans from Africa have been found to have connections with modern diseases such as obesity, diabetes, and cardiovascular disorders. These adaptations, which arose during the ancient migration and settlement of human populations, have established genetic variations that are now associated with common health conditions in modern times.

In a separate study, we proposed that genes that were advantageous in the past may contribute to the susceptibility of present-day humans to various diseases. By identifying the specific genetic targets of historical adaptation events, we can potentially develop therapeutic strategies and preventive measures that cater to the needs of contemporary populations.

Our research adds to the growing body of evidence highlighting the significant role of adaptation in shaping the course of human history. Moreover, it underscores the increasing potential of evolutionary genetics in advancing medical research, offering valuable insights into the genetic underpinnings of common diseases and paving the way for innovative approaches to healthcare.

Source: The Conversation

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