Cave painting of a bull.

The Evolutionary History of Hominins

What are Hominins?

Hominins are the species that belong to the genera of Homo, Australopithecus, Paranthropus and Ardipithecus. . Members of the genus Homo have brains that are large, relative to their body size, smaller and flatter faces, smaller jaws and teeth, and increased reliance on culture. Species in the genus Homo also are less sexually dimorphic than other animals. Sexual dimorphism is defined as the differences between males and females of a species. The most defining characteristic of hominins is bipedalism.

First Hominins

Orrorin tugenensis

The oldest definitive bipedal human ancestor is Orrorin tugenensisi. Researchers chose this name because Orrorin means original man. Fossils of femurs, fingers, arms, and cranial bones provide evidence of bipedalism. Unfortunately, researchers have not been able to acquire a sizable collection of Orrorin tugenensis fossils. Additionally, the fossils date to between 6 and 5.7 million years. The shape of the finger bones suggests that Orrorin tugenensis was a climber.

Ardipithecus Genus

We know quite a bit about the species Ardipithecus ramidus because of a robust collection of fossils. The species was bipedal, but this adaptation was fairly new. The evidence for this is Ardipithecus ramidus’ opposable big toe. This foot morphology is associated with climbing and is also found in chimpanzees. Another species in the Ardipithecus genus is Ardipithecus kadabba. The difference between A. ramidus and A. kadabba is dental structure. Ardipithecus kadabba lived about 5.2 million years ago.

Ardipithecus ramidus skull
Ardipithecus ramidus
Credit: Australian Museum

Australopithecus Genus

Gracile Australopithecines

Gracile australopithecines lived in East Africa, and the oldest known specimen dates to between 4.2 and 3.8 million years ago. The most well-known gracile australopithecine is A. afarensis. In fact, the famous Lucy specimen belongs to the A. afarensis species. Another famous find associated with A. afarensis is the Laetoli footprints. This site consists of a trail of footprints preserved in volcanic ash. The prints show that the structure of the australopithecine foot suggests bipedalism. Compared to modern humans, gracile australopithecines had much larger molars and canines. They also had protruding lower faces. It is still up for debate if australopithecines used stone tools.

Robust Australopithecines

Robust australopithecines had larger teeth and chewing muscles than gracile australopithecines. These dental differences also reflect a difference in diet. Robust australopithecines had a more specialized diet, while gracile australopithecines were generalists. The genus name for robust australopithecines is Paranthropus. Members of this genus ate rough, fibrous plants. The flat premolars characteristic of the Paranthropus genus allowed them to grind down plant material.They also ate meat. The first discovered Paranthropus species is Paranthropus robustus. This species lived 2 million years ago. Another species in the Paranthropus genus is P. boisei. This species lived 2.4 to 1.4 million years ago. It is possible that they used stone tools, but the evidence is inconclusive.

Paranthropus boisei skull
Paranthropus boisei

Early Members of Genus Homo

Homo habilis

The earliest Homo species is Homo habilis. The oldest specimens of this species date to 2.8-2.5 million years old. Homo habilis individuals used rudimentary stone tools. In fact, the name Homo habilis means handy man. The tools this species used are categorized as the Oldowan tradition. Oldowan tools used for chopping are stones with flakes missing from one end. The removed flakes were used for cutting also. Homo habilis scavenged for their food. They would butcher and consume the carcasses other animals had already abandoned. Their use of tools allowed them to acquire the bone marrow from carcasses, as other species were not equipped to harvest this nutritious resource.

Homo erectus 

Homo erectus had a larger brain, larger body, and smaller teeth than Homo habilis. Anthropologists have found fossil evidence of this species in Asia and Africa. Homo erectus created the Acheulean tool tradition. These tools are much more complex than Oldowan tools. Acheulean handaxes are bifacially flaked. Bifacial flaking is a technique where flakes are removed from the front and back of the stone. Other Acheulean tools include cleavers, scrappers, and cutting flakes. Notably, only the Homo erectus in Africa used Acheulean tools. There is nearly no evidence of Acheulean tools in Homo erectus sites in Asia, but Oldowan tradition tools are present. Researchers have proposed this is the case because Homo erectus populations used tools made of bamboo. Another possibility is that the Asian Homo erectus populations migrated to the area before the Acheulean tradition developed.

Nearly complete Homo erectus skeleton.
Homo erectus
Credit: Chip Clark

Homo neanderthalensis

 Geographic Region and Morphology

Homo neanderthalensis, also known as neanderthals, went extinct about 35,000 years ago. The earliest known specimens of the species date to 150,000 years ago. Neanderthals inhabited western Europe, the Middle East, and western Asia. Neanderthal encampments were located in extremely cold climates, as they lived during the last Ice Age. They were nomadic, following the animals they hunted as they grazed. Compared to Homo sapiensHomo neanderthalensis had a more powerful, sturdy build. Neanderthals had a pronounced brow ridge, a large and broad nose, and a large jaw. Interestingly, neanderthals had teeth the same size as humans, but their large jaw meant that there was a space behind their last molar. This is called a retromolar gap.

Tool Use and Hunting Practices

The stone tool culture of Homo neanderthalensis is called the Mousterian tradition. The Mousterian tool kit contained a variety of specialized tools. Neanderthals had different tools for butchering, woodworking, antler working, and hide working. Mousterian tools were much lighter than the tools of previous traditions. This meant that neanderthals could haft them on wooden or antler handles. They used tar to stick the blade to the shaft. Neanderthals made the tar from birch bark. Notably, neanderthal use of adhesive predates Homo sapien adhesive use by 100,000 years. The technique of hafting allowed Homo neanderthalensis to make spears. Because of this new technology, neanderthals were able to hunt instead of relying on scavenging.

Neanderthals hunted deer, horses, and the early ancestor of cows. Hunting was very risky, however, as neanderthals did not have any projectile weapons. This meant they hunted at close range and in groups to reduce risk. Many neanderthals were severely injured or killed when hunting. There is evidence that neanderthal communities took care of individuals with such injuries. They also buried their dead. It is amazing to see such great compassion in our ancestors, as it disproves the idea that cavemen were brutish and unfeeling.

Reconstruction of the appearance of a male neanderthal.

Genus Homo Outliers

Homo naledi

The Homo naledi species is unique because it had some characteristics of much earlier hominins. They had skulls of a similar shape to other members of the Homo genus, as well as similar teeth. Homo naledi had a much smaller brain, however, and curved fingers that are similar to primates that live in the trees. This species lived 335,000 to 236,000 years ago. This is shocking because Homo sapiens also existed during this time. The case of Homo naledi shows that human evolution was not as straight-forward as previously believed.

Homo floresiensis

Homo florensiensis is another species that does not fit into our previous view of evolution. A female specimen of the species was found on Indonesia’s Flores island. This species had a skull and brain similar to the much earlier Homo erectus. Homo florensiensis was about 3 feet tall and weighed about 66 pounds. Because of the species small size, researchers gave it the nickname “the Hobbit”. One reason for the species small size could be insular dwarfism. Insular dwarfism is the phenomenon where animals evolve to be smaller because they live in a limited environment, such as an island. Smaller species do not need as much food, which is essential when one lives in geographic isolation. Homo floresiensis lived 100,000 to 60,000 years ago. Evidence of stone tools found near Homo floresiensis remains indicate that the species was a hunter.

Archaic Homo sapiens

While archaic Homo sapiens and modern Homo sapiens belong to the same species, differences have emerged due to continued evolution. Archaic Homo sapiens had skulls that were less rounded than those of modern Homo sapiens, and they had much smaller foreheads. Archaic Homo sapiens also had wider noses, a slightly protruding face, no chin, and bulkier bones. In other words, archaic Homo sapiens retained features of the earlier Homo erectus. Archaic Homo sapiens lived between 600,000 and 200,000 years ago. Archaic Homo sapiens entered the fossil record 600,000 years ago in Africa, 350,000 years ago in Europe, and 300,000 years ago in Asia.

Modern Homo sapiens 

Morphology and Evolution

Compared to archaic Homo sapiens, modern Homo sapiens have slightly larger brains, a smaller brow ridge, smaller teeth, and a thinner face. Modern Homo sapiens evolved from the archaic Homo sapiens population of Africa. It is important to note that this was not a linear process. Fossil evidence shows individuals had a mix of modern and archaic traits, and there was variation in the traits present.

Increasing Habitat

The first place after Africa to be inhabited by modern humans was the Middle East, and the earliest found remains date to 194,000 to 177,000 years ago. Modern humans lived in China as far back as 120,000 years ago. Homo sapiens came to Australia. They used a series of land bridges and land masses that no longer exist to reach the region. After East Asia and Australia, Europe was inhabited next. This occurred at least 40,000 years ago. Prior neanderthal settlements and the lack of specializations for cold weather are possible factors in the later arrival to Europe.

Culture

Researcheres believe more complex culture developed in Africa during the mid to late Stone Age. Evidence for this was found in Blombos Cave located in the Cape of Africa. Archeologists recovered 100,000 year old tools to process ochre. Ochre is a type of vibrantly colored clay and was often used as paint. Marine snail shell beads dating to 75,000 years ago were also found at the same site. These finds show that ancient peoples were now using their natural resources for artistic expression, not just survival.

Cultural innovation was also occuring in Europe. Archeologists have found beads and figurines of female bodies. Hunting technology was also developing. The people of the Gravettian culture (6,000 to 21,000 years ago) developed the atlatl. The atlatl is a type of spear-thrower. This invention made hunting much safer, as one does not have to get as close to the animal when using projecticle weapons. One famous site showing a more complex culture is Chauvet-Pont-d’Arc Cave in France. This site contains a collection of cave paintings. Depictions of deer, horses, rhinos, owls, and other animals cover the walls. Two of the figures might depict humans, but it is not clear. These images date to 31,000 to 26,000 years ago.

One thing that must be mentioned when talking about ancient paintings is the fact that they are almost always found in caves. The first assumption one might make is that past peoples only painted in caves and that there must be some symbolic significance to such landforms. This could be true, but I think it is more likely that past peoples painted on other surfaces, but they no longer exist due to weathering. The reason anthropologists only find ancient paintings in caves is because the closed nature of caves allows for the art to be preserved.

Cave painting of a bull.

Conclusion: Respecting the Humanity of Hominins

I sincerely hope with this article I have shown that the stereotype of aggressive, selfish cavemen is completely false. Evidence of group hunting, the treatment of the sick and dying, the creation of complex tools, and symbolic culture all show that the hominins of the past were caring and intelligent. History is spun to justify the ideals of today, and I believe this is partially the reason that hominins are depicted as so competitive and unfeeling in the media. This view of past peoples justifies the fierce independence that American society values. The truth of the matter is that past hominins survived through cooperation and compassion. Humans are social creatures, we should not feel ashamed for needing the support of others.

I do not believe the negative depiction of past hominins in the media is completely malicious, however. A movie about cavemen where they behave like modern humans would not be very interesting. People watch movies to see something new and exciting, not to see regular people making tools and coexisting.

Anthropology is so important because it allows us to learn about our history with as little cultural bias as possible. When this bias is removed, it becomes clear that even people separated by time and space are not so different. The hominins of the past felt the emotions we feel. They lived and died on the same planet we stand on today. We must respect their experiences because humanity would not be here without their rich culture and innovations. History is very powerful, and anthropology makes sure the events that occurred and the history we are told align. I hope anthropological efforts will lead to a more positive view of our hominin ancestors.

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