Our family of hominins started out small. For much of human evolution, our species, genus, and even family lived in small groups of a few dozen to a few hundred people. The first fossils belonging to our genus, Homo, were found in Africa, and dates suggest that our ancestors first arrived there about 2 million years ago. Our oldest known human ancestor, Australopithecus, lived no more than 4 to 5 million years ago. Modern humans and their neandertal ancestors, Homo sapiens and Neanderthalens, split off from the A. sapiens group about 600,000 years ago, and our most recent common ancestor, LCA, lived about 250,000 years ago (O’Higgins, 2011).
These days, we think of humans as being extremely sociable creatures. Although we are biologically adapted to live in small groups, we have a proclivity for wanting to be with other people. The rise of civilization and the formation of tribes brought about a large-scale reorganization of human society with families moving away from living in small groups and more relying on social media to stay connected.
The Oldowan site in northern Kenya is famous for its 2.77 million-year-old fossils. Excavations of the Oldowan site began in earnest in 1963 and continued until 1967, yielding a remarkable abundance of fossils documenting the evolution of our genus. Most notably, the site contained the fossilized remains of at least 27 individuals from at least seven different species of hominins. The discovery of these fossils established Oldowan as the “mother lode” of hominin paleontology. However, some scientists feel that the material originally attributed to the species, Paranthropus, is probably attributable to another hominin, A. africanus. The fossilized remains of these two hominins were indistinguishable, so the question of their taxonomic relationship has plagued paleontologists ever since (Lovejoy, 2016). What is remarkable about this dispute is that it is entirely theoretical, and there is no question that the fossils actually belong to two species that coexisted.
Since its discovery, the Oldowan site has yielded many important insights into our evolutionary past. For one, it suggests that early hominins were ecologically flexible, able to exploit a variety of habitats. The presence of these hominins in North Africa as well as in neighboring regions such as the Middle East gives credence to the possibility that modern humans and certain ancestral species of hominins embarked on a long-distance migration from the Levant (the area between Egypt and Syria) to North Africa about 35,000 to 50,000 years ago (López-García and Simmons, 2016). It also provides important insights into the paleoclimate of the Pleistocene period, which is now recognized as having been exceptionally harsh, with lots of temperature fluctuations.
A Variety of Hominins at the Site
The Oldowan site is incredibly rich in hominin fossils, with a minimum of 27 individuals being uncovered from at least seven different species. This site also happens to be the location of Mount Kulan in the Afar Region of Ethiopia, which is considered by some to be the birthplace of mankind (Turkana Boy). Excavations at the Oldowan site began in earnest in 1963 and continued until 1967, revealing a remarkable abundance of fossils documenting the evolution of our genus. After a relatively sedentary lifestyle during the Pleistocene, the first of these hominins, Homo erectus, began expanding their range as a result of the gradually increasing temperatures caused by climate change. This hominin, in particular, has a reputation for being exceptionally agile and innovative, traits that allowed them to adapt to their changing environment.
About 1.8 million years ago, our ancestors began developing more sophisticated stone tools, such as knives, sickles, and arrowheads. These tools were not only used for hunting, but were also useful in processing plant foods. Unfortunately, the increasing use of these tools also resulted in a spike in human mortality caused by injuries and infections sustained from the frequent use of these sharp weapons. This trend continued until about 600,000 years ago, when the use of bows and arrows for hunting gave way to spears and arrows. These were less dangerous to handle, but posed a greater threat to animal and human lives due to their greater piercing capacity. The invention of fire also played a significant role in our evolutionary progress by allowing our ancestors to more easily process the foods that they hunted or gathered. The use of fire in this way is considered the archetypal “tobacco break,” as it was originally used to roll cigarettes and as an inhalant. Another significant development that occurred about 600,000 years ago was the use of clothes, which initially evolved as a means of keeping warm and dry, and as a way of signaling group identity.
Paranthropus as a Second Genu
One of the most enigmatic and intriguing discoveries at the Oldowan site is the fossilized remains of a hominin measuring 6 feet 7 inches tall, named Paranthropus. This individual, estimated to be between 40,000 and 45,000 years old, was a biped with a large cranial capacity. The combination of these two characteristics suggests that Paranthropus is likely the same species as A. africanus, and not P. robustus, as previously believed. However, the cranial capacity of this individual is nearly identical to that of Homo erectus, which suggests that A. africanus and Paranthropuswere closely related. The discovery of this individual in 1962, as well as a second one uncovered the same year at Leshan, China, demonstrated that early hominins were more diverse in geographical distribution than previously believed (Bond, 1965). This is also reflected in the variety of species that the genus, Homo, evolved from.
Homo erectus as a Species Redundant With Modern Humans
In recent years, many scientists have questioned whether the species, Homo erectus, is truly extinct. The emergence of modern humans, Homo sapiens, about 200,000 years ago has led some paleontologists to suggest that this species may be genetically redundant, meaning that there exists a close relative that could carry on the species. One of the most promising candidates for revival of this species is the Neanderthal, Neanderthalens.
About one-quarter of a million years ago, our ancestors began leaving Africa and slowly expanding their range, first to the Middle East and then to Europe, where they were soon followed by Homo sapiens. During this time, Homo erectus was one of the first hominin species to arrive in Europe. However, the extinction of the Neanderthal about 35,000 years ago caused the species to be genetically isolated. The last fossilized evidence of the Neanderthal dates back about 30,000 years ago, so it is considered to be an “extinct” species. This is in contrast to Homo sapiens, which is still considered to be a “living” species.