The journey of humankind

By: Irene Cohen and Ellie Mulvaney

Since the beginning of the earth, from the first single celled organisms to modern species, evolution has developed life as we know it. We see variance in this evolution all around us in the diverse animals that span our environment (for example, the genus canis includes the species: wolfs, dogs, jackals, and coyotes).

With many examples in nature such as this, a frequent question refers to whether or not modern day humans (genus homo) have separate species. Race, though sometimes believed to be, is not a difference in species. Humans everywhere are Homo sapiens, no matter the slight phenotypical differences between them.

To understand this, we have to go back in time to the earliest humans. According to Britannica, ape-like species, around 16-5.3 million years ago (also known as the Middle and Late Miocene Epoch), lead to the first humans. Based on genetic information, scientists are confident that, more specifically, they existed in the later years (11.6-5.3 million years ago).

These primates from Eurasia and Africa are assumed to have become the first Hominins, or the beginnings of human lineage, in the Pliocene Epoch. Among the species that were developed in that era, Graecopithecus, prevailed as ancestral to the following: Australopithecus, Parenthropus, and Homo of the human lineage, while some additionally believe that great apes such as Pan (chimpanzees and bonobos) and Gorilla also came from the species Graecopithecus.

The catalyst for the aforementioned Hominins, was the climatic changes in the Miocene Epoch, as told by BBC.. Forests were replaced by open plains and prairies, which benefited terrestrial life. This meant walking creatures had advantages over terrestrial, or tree-living, creatures, which was a defining factor in the development of bipedalism (the trait of walking on two feet).

Bipedalism is a defining feature of humankind, and though it is not exclusive to humans, we are the only mammalian bipeds to solely use it, while others combine jumping and waddling. Humans advanced further and further into this bipedalism to survive, being able to run away from predators and quickly find food.

As reported by Nature.com, the species Homo sapien, as we now know it, evolved in Africa 315,000 years ago. At the time, Homo sapiens lived alongside Neanderthals and Denisovans (both of which were branches of humanity that are now extinct), and also occasionally interbred, resulting in Neanderthal DNA in most humans excluding those originating from Africa.

The fossils of this species have been found in Europe and West Asia, while the less common Denisovan fossils have been found in Eastern Asia, just 12 years ago.

Neanderthals were defined by their large noses and prominent brow ridges. In stature, they were short and stocky, and had a long, low skull. Overall, they were more compressed and ape-like than humans today, weighing in at anywhere between 64-82kg. They had large front teeth for tough food, and a weak chin, alongside a wide nose, which is theorized to have helped internally warm and moisten the air in their colder environment.

While there is not enough fossil evidence to recreate the appearance of Denisovans, the genetics that we have received lead many scientists to agree on some key features. They may have had a wider jaw and skull, and are theorized to have large molar teeth. This was concluded from a Denisovan jaw bone that was found sporting a high dental arch that suggested the adaptation.

These species went extinct through a pure example of survival of the fittest. Natural selection ran its course as population increased, and, consequently, so did competition.

As mentioned above, climate conditions changed and food became more scarce, leading to a higher death rate. By chance, the random variation that made homosapiens unique, were well suited to these changes and they survived over their counterparts.

Overall, humans did once have multiple species, but one has reigned successfully to become the sole remaining Homo sapiens.

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