An overview of early hominids – part one

For millions of years before Homo sapiens proliferated on Earth and colonized the globe, numerous different species within the Homo genus existed on the modern continent of Africa. This series of articles is dedicated to synthesizing information pertaining to human’s earliest ancestors.

The chimpanzee-human last common ancestor (CHLCA)

The chimpanzee-human last common ancestor (CHLCA) can be described as the final common ancestor between the genuses of Pan (chimpanzees and bonobos), and Homo (humans). The divergence between these two genuses is hotly debated between modern historians, and there is no evidence that points to one particular species as being the CHLCA.

In order to facilitate our understanding of human evolution, it is important to mention that there was once a time where the Homo genus ceased to exist. Modern Homo sapiens are the result of millions of years of mammalian evolution during the Cenozoic era.

Once again, there is no succinct evidence pointing to any one species as the CHLCA. However, many of the early hominids that I will be mentioning in this article have been theorized to be candidates for the position.

Sahelanthropus tchadensis, one of the earliest hominids

Although we haven’t reached the genus Homo on our evolutionary journey quite yet, Sahelanthropus tchadensis is still considered to be a hominin by modern historians.

With regard to our timeline of hominids, you’ll see that S. tchadensis is an outlier, living in and around Northern Africa around 7 million years ago. Although there were other hominids living during this time period (Graecopithecus, Oreopithicus, etc), S. tchadensis was unique in its ability to walk upright. As this particular species was unique in that it was one of the earliest bipedal hominids, it is viewed as a major landmark in the evolution of modern Homo sapiens.

However, S. tchadensis continues to be debated within the historical world. It is theorized that because S. tchadensis existed so long ago, and that it exhibited many ape-like attributes, there’s still a possibility that it is more closely related to Pan than Homo.

Orrorin tugenensis

The genus of Orrorin was discovered as recently as 2001, in the Tugen Hills of Kenya. Orrorin tugenensis was similar to S. tchadensis in the sense that it also was a probably ancestor to modern humans, but also exhibited more ape-like features than human ones. However, the human-like traits that Orrorin exhibited cannot be discounted. Pickford and Senut, the lead paleoanthropologists that discovered O. tugenensis, detailed in their article for the South African Journal of Science that O. tugenensis exhibited many dental similarities when compared to modern humans. “Thus, 6 million years ago in Kenya, there was a bipedal hominid which was closer in size and morphology to extant humans than the much younger australopithecines and Ardipithecus ramidus.”

With regard to vocabulary – australopithecines and Ardipithecus ramidus are two much more recent hominids, and the student of anthropology would expect for these younger species to exhibit more physical attributes that are similar to those of the modern human. However, the discovery of O. tugenensis complicates things.

This species is the perfect example of how anthropology continues to evolve in itself, and that someone can find fragmentary remains of an early hominid that results in our understanding of human evolution becoming complicated again.

In summary

It is pivotal to our understanding of human evolution that these two early hominids developed a penchant for bipedalism. Due to the fact that this trait was exhibited so early in the scale of human evolutionary time, it continues to convolute our understanding of how to place exactly where we originate from, and where exactly our genus diverged from chimpanzees. However, historians and anthropologists are still making new discoveries every day, further advancing our understanding of human evolution.

Further reading, sources

Pickford, Martin, & Senut, Brigitte (2001). Millennium Ancestor. journals.co.za.

Also, check out the interactive timeline of hominids on the Smithsonian National Museum of Natural History’s website: https://humanorigins.si.edu/evidence/human-evolution-interactive-timeline