Why Did Denisovans and Homo sapiens Meet Around 50,000 Years Ago? — Here’s What Researchers Discovered Happened Next

The modern human species, Homo sapiens, was not the only human alive around 50,000 years ago. Another human species that existed back then was the Denisovans. They are believed to have lived in Asia and Oceania, from 200,000 to 40,000 years ago. But, before they disappeared, scientists discovered that they may have met with Homo sapiens.

Our ancestors were thought to have originated and evolved in Africa. For over 200,000 years, we have survived in that continent; however, around 70,000 to 50,000 years ago, the anatomically modern humans migrated out to Europe and Asia. This is most likely when they met other archaic humans, such as the Denisovans. But why exactly did they meet? Is it coincidental, and how did their meeting change the trajectory of human history? Let’s dive deep into the past in this article.

Why They Met — Migration and Overlapping Territories

The biggest factor why Homo sapiens and Denisovans met was migration. Around 70,000 to 50,000 years ago, modern humans ventured out of Africa because of several reasons. The most significant one was climate change affecting their natural habitats, which is a phenomenon that led to cooler and drier periods in Africa. This forced the population to find a better environment with more abundant resources.

It is believed that Homo sapiens likely followed temporary green corridors or wet vegetated areas in the Sahara and Arabian Peninsula that existed from time to time. The animal herds could have also done the same, and the humans tracked them down to find food and water sources, until they ventured out of the continent and reached Eurasia.

As they spread eastward, they bump into another archaic human group that is already living and has established itself in the area. Denisovans were believed to have occupied several parts of Asia, including Siberia and the Southeast regions. There are fossils like the Xiahe mandible, which also showed that they lived in high-altitude places and have developed unique adaptations to survive in these environments, like in the Tibetan Plateau.

Read more: Wikipedia

Evidence They Mixed — DNA Clues and Genetic Signals

A Brief History Of The Mysterious Homo Species: Denisovans

So, what happened next when the two different human species met? Well, it is believed that they interbred and might have even shared culture and knowledge with one another. The strongest evidence of this theory was found in comparing the Denisovans’ ancient DNA with modern-day humans.

The population in Oceania, South East Asia, and Papua New Guinea carries a high percentage of Denisovan DNA, with some specific groups reaching up to 4 to 6% of their genes coming from these archaic humans. There was also some clue that the interbreeding did not only happen once in a particular group.

Scientists believe that they detected introgression where bits of Denisovan DNA were inserted into the modern human species in multiple pulses. In other words, Homo sapiens may have mated with different groups of Denisovans at different times. These are clues and evidence that exist even today, reminding us that once upon a time, we were not the only human beings on the planet.

What Happened Next — Gene Sharing, Adaptation, and Diversity

So, after the two different human groups met and interbred, what happened next? Because, as we currently know, Denisovans have become extinct, while Homo sapiens has become the dominant and only human species on the planet today. First, there was the gene flow and passing of different traits and characteristics to one another.

Denisovans lived in a variety of environments, such as High-altitude places like Tibet and hot tropical regions like Southeast Asia, so they likely developed a wide range of adaptations. Homo sapiens, on the other hand, have adapted to the diverse environment of Africa, but still may not have had enough traits to survive in the new habitats they just migrated to.

But, because of the meeting and interbreeding with Denisovans, some of their helpful genetic traits and adaptations could have been passed on to Homo sapiens. An example of this was the EPAS1 gene variant that the Tibetan population still has up to this day. This is a unique trait that came from the Denisovans, which allowed them to efficiently regulate oxygen circulation in the body to avoid sickness related to the high altitude habitats.

Secondly, the mixing of genes most likely not only helps Homo sapiens by receiving traits that would allow them to survive in the new environments, but it also adds to the rich and diverse gene pool. Having more alleles and diversity in their genes could mean a population is more resilient to biological diseases, natural disasters, and changing conditions.

Read more: Nature Genetics

Challenges, Decline, and Legacy

Another Species of Human? The Truth About Denisovans

Even though Denisovans once thrived, surviving for hundreds of thousands of years in different environments, including harsh habitats, they still faced several challenges that may have eventually led to their demise. Some of these problems were the environmental shifts and climate fluctuations.

These phenomena would have made some of their habitats unlivable because of the scarcity of resources. Then they also faced competition with Homo sapiens after they arrived in their territories. Some groups may have just met, interbred, and even shared culture, but a competitive relationship could also be the reality.

Homo sapiens were believed to have an advantage in their numbers, as our species often lives in larger groups or populations compared to most other hominins. This could have given us an advantage during intercompetition with other humans. Denisovans, on the other hand, are a lower population group and possibly fragmented and isolated due to some of their natural habitats.

An isolated population is more prone to inbreeding, genetic diseases and is more likely to be wiped out if it faces a problem they are not adapted to. The combinations of these factors are probably what made the Denisovans disappear, but it could also be that our species absorbed or merged with them. Regardless, their legacy still lives with us even today.

Author's Final Thoughts

Denisovans are one of the archaic humans that once lived with us on this planet. They adapted to different environments and likely evolved some genetic traits that Homo sapiens were able to benefit from after they met and interbred with them. Without the Denisovans, the history of modern humans could have very well followed a different trajectory.

So, while the Denisovans went extinct now, the fact that humans from different parts of the world still have and benefit from their DNA reminds us that this ancient encounter is not a simple story. Rather, it is a complex interplay of human relationships, interactions, migrations, and adaptations that, even today, still influence our existence and history.

Read next: Why Did Human Intelligence Rapidly Expand Between 800,000 and 200,000 Years Ago? — Here’s What Scientists Suggest

References & Further Reading

Meyer, M., et al. (2012). A high-coverage genome sequence from an archaic Denisovan individual. Science. https://doi.org/10.1126/science.1224344

Browning, S. R., et al. (2018). Analysis of human sequence data reveals two pulses of archaic Denisovan admixture. Cell. https://www.cell.com/fulltext/S0092-8674(18)30175-2

Jacobs, G. S., et al. (2019). Multiple deeply divergent Denisovan ancestries in Papuans. Cell. https://www.cell.com/cell/fulltext/S0092-8674(19)30218-1

Huerta-Sánchez, E., et al. (2014). Altitude adaptation in Tibetans caused by introgression of Denisovan-like DNA. Nature. https://www.nature.com/articles/nature13408

Slon, V., et al. (2018). The genome of the offspring of a Neanderthal mother and a Denisovan father. Nature. https://www.nature.com/articles/s41586-018-0455-x