What could be the reason behind the existence of only one human species today?

Margie Jones
12/10/2023

According to evidences found, at least 21 human species existed in the history, but mysteriously only one of them is alive right now.

The Smithsonian National Museum of Natural History has listed at least 21 human species that are recognized by most scientists. These ancient human species, known as hominins, span a time period of approximately six million years. From Homo habilis, who lived around 2.8 million years ago, to Homo neanderthalensis, who disappeared just 40,000 years ago, each species had its own unique characteristics and adaptations.

18 of the most distinctive hominins. Smithsonian National Museum of Natural History / Fair Use

This incredible diversity raises an intriguing question – why is it that only Homo sapiens, our species, survived and thrived while the others perished? Scientists have been grappling with this mystery for years, exploring various theories and analyzing countless pieces of evidence.

One prevailing theory suggests that Homo sapiens, with their cognitive abilities, were simply better equipped to adapt to changing environments and outcompete other hominin species. Our unique combination of intelligence, language skills, and advanced social structures might have given us the upper hand in survival and reproduction.

Oxygen isotope curve (δ18O) for the past 10 million years (data from Zachos et al., 2001). The changing climate of Earth has been determined through various methods. One significant method is the examination of oxygen isotopes, particularly δ18O, found in the microscopic skeletons of foraminifera. By analyzing these isotopes, scientists can determine the temperature changes and presence of glacial ice throughout history. This analysis reveals two main trends: a general decrease in temperature and a greater degree of climate variation over time. Interestingly, the later stages of human evolution experienced more environmental fluctuations than the earlier stages. Smithsonian Institution / Fair Use

Another possibility is that interbreeding and genetic assimilation occurred between different hominin species. Recent research has found evidence of interbreeding between Homo sapiens and Neanderthals, as well as with other ancient hominins such as Denisovans. These interactions might have resulted in the absorption of certain genetic traits from other species, enhancing the adaptability and resilience of Homo sapiens.

However, the scarcity of fossil evidence, especially from time periods where multiple species coexisted, makes it difficult to definitively prove these theories. The fossil record is incomplete and fragmented, leaving many gaps in our understanding of human evolution.

In recent years, advancements in genetic analysis have provided new insights into our evolutionary history. By extracting and analyzing DNA from ancient hominin remains, scientists have been able to uncover crucial information about our genetic connections to other species. These studies have revealed surprising discoveries, such as the presence of Neanderthal DNA in the genomes of modern humans.

Furthermore, the study of ancient hominin DNA has also revealed the existence of some previously unknown human species. For instance, the discovery of the Denisovans in Siberia was made possible through genetic analysis of a finger bone fragment found in a cave. This highlights the potential for future discoveries and the uncharted territory that still remains in our understanding of human evolution.

Ultimately, the question of why only one species – Homo sapiens – survived remains unanswered. Exploring this mystery is not only crucial for our grasping the past but can also shed light on our future as a species. By studying our evolutionary journey and the factors that led to our survival, we can gain a separate window into the challenges and opportunities that lie ahead.

As we continue to uncover new evidence and refine our theories, we must remain open to the possibility that the story of human evolution is far more complex and interconnected than we currently comprehend. Perhaps in time, we will unlock the secrets of our ancient ancestors, and in doing so, gain a deeper understanding of ourselves.

In the end, humans today are the only species that has survived out of the diversity of hominin species. Even though these species were similar to us and possessed some combination of features that characterize humans today, they are now extinct. We need to see how well we can adapt to changes in our environment caused by our actions and natural shifts.

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