[From the Archives] The Enigmatic Homo erectus: The First Transcontinental Wanderer

Homo erectus was an ancient early human species that was the first of our kind to leave Africa and the longest-lived species of human ancestors. How did this species survive for so long?

Unraveling the story of human evolution proves to be an enigmatic project filled with awe and wonder. Image credit: Olof Åkerlund, Sveriges Radio.

Greetings, fellow wanderers,

Today I am republishing another post from the archives. As Those Who Wander acquires newer subscribers, I recognize that many newcomers may not have access to or be familiar with some of my initial writings. With over 100 posts in the archive, I want to expose these paywalled posts to more readers.

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Now onto today’s archived post, The Enigmatic Homo erectus: The First Transcontinental Wanderer

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Although we may fancy ourselves a global species, Homo sapiens was not the first transcontinental wanderer. That title belongs to Homo erectus. Of the more than 20 hominin species that have been discovered and classified by paleoanthropologists, Homo erectus is, by far, the most intriguing and enigmatic early human to my anthropological mind. Enigmatic because what we know about Homo erectus only elicits more questions. For instance, knowing that this species lived from 1.89 million to 110,000 years ago (nearly nine times as long as our species has been around) only begs the question of how they managed to survive for such an incredibly long time. 

What does it mean for the Homo erectus living 1.89 million years ago and the one living 110,000 years ago to still be considered the “same species”? This would be equivalent to saying that 1.5 million years into the future, our species would still be considered nearly identical to who and what we are today.

There are simply far too many interesting facts and questions about Homo erectus to be covered in one sitting. But here are some of the more notable features of our ancient hominin cousins.

Artistic rendering of the skeleton and life reconstruction of the famous Homo erectus specimen known as ‘Turkana Boy’ by paleoartist Mauricio Antón

Brain Size

The cranial capacity or brain size of hominins is often measured in cubic centimeters (cc). These measurements give us a standardized way to compare the overall shape and size (or morphology) of bones like the skull to see how a given specimen varies within its own species as well as measure up to other similar species like modern humans. The brain size and various other features of the skeleton give us clues into how early humans evolved.

The shape and size (or morphology) of a Homo erectus skull (left) compared to a modern human skull (right).

One of the incredible things about the collected and measured skulls of Homo erectus is that their brain size varies tremendously, with the smallest being around 550 cc and the largest being around 1250 cc, with the average being around 900 cc. Modern human brain size has a smaller range from 1350-1600 cc, with an average of around 1400 cc. This immense variation may be expected for a species that survived most of the geological epoch known as the Pleistocene, as that long duration of time mixed with many different environmental influences guided the evolutionary pressures to ever so slightly tweak and modify the features (or phenotypes) of Homo erectus.

Although it is doubtful (though not certain) that they had anything like language, Homo erectus may have possessed something like a proto-language using a combination of symbolic communication that used hand signals, facial gestures, and various nasal expressions, sounds, and grunts not unlike some modern apes.

Technological Innovations

Homo erectus is famous for developing one of the world’s first technological revolutions—known as the Acheulian industry. The term “industry” might be a stretch, given how quaint the technology is when compared to the computer or the Saturn V rocket. But that doesn’t mean these tools should be underestimated. Though seemingly modest, the ability of someone to have the dexterity, hand-eye coordination, foresight, and cognitive capacity to craft an Acheulian handaxe is what makes the development of such a tool so remarkable.

And yet, despite the intelligence required to obtain and manufacture these objects, one of the remaining enigmas about Homo erectus is why this technology did not change for over a million years. This would be the equivalent of us still using the printing press today from when it was first invented in the 1430s and being content to carry on with this technology for another 999,416 years without any modifications! Indeed, our modern capacity to innovate to rapidly seems a hallmark exclusive to our species.

An illustration demonstrating the process of breaking down a stone to form the finished product of an Acheulian hand axe.

Nevertheless, the other extraordinary cognitive leap involved in this technology was that one had to possess the mental capacity to know which stones could be broken down and sculpted in such a way as to produce a reliable handaxe for cutting and breaking down animal carcasses. Not all stones are equal. Many rocks are brittle and useless, and the useful ones are not all distributed on the landscape equally. One had to learn and memorize where specific locations were to extract and then produce these tools.

Anyone who has tried to flint-knap and make these traditional stone tools (and I encourage any reader to give it a try at some point), will quickly learn to appreciate the challenges involved in their manufacturing.

A second and more profound technology, or perhaps discovery, that may be attributed to Homo erectus is the use of fire. I wrote in a previous post that fire is arguably the most important human discovery ever made. Although evidence is limited (campfires rarely preserve well over millions of years) and there is no scientific consensus on the matter, there have been some sites to suggest Homo erectus used fire in some capacity. Koobi Fora in Kenya has been dated to around 1.5 million years ago, and Wonderwek Cave in South Africa has been dated to 1.7 million years ago, both potentially linking Homo erectus to utilizing fire.

This doesn’t necessarily mean Homo erectus was making fire per se, but that they could have gathered fire or embers from naturally occurring fire sources such as lava flows or fires started from lightning strikes, and thus maintained the fires for prolonged periods. Nevertheless, this is still a remarkable cognitive skill set to have developed because maintaining a fire also requires knowledge of slow-burning materials and how to doctor the embers to keep them aglow. It is still unclear just how much Homo erectus was utilizing fire since the archaeological record only begins to witness widespread use of fire around 400,000 years ago. What’s more, distinguishing natural brush fires from artificially made campfires can prove challenging archaeologically.

Many questions remain. Did they only use fire opportunistically, or did many sites not get preserved over this vast period? Or perhaps the discovery of fire and knowledge of how to use it was lost and rediscovered many times over their existence, what might be thought of as recurring dark ages in the early hominin past. Hence, the enigmatic Homo erectus still perplexes!

Famous Specimens and Distribution of Sites

Many Homo erectus specimens have been discovered throughout Africa and Eurasia, the most famous being Java Man, discovered by Eugène Dubois in Indonesia in 1891, and Peking Man from Zhoukoudian Cave in China in 1921. Due to the early discovery of these specimens in Asia, many early researchers were convinced Asia was the birthplace of humankind. Charles Darwin, in his 1871 book The Descent of Man, was later proven correct in his claim that Africa was, in fact, the birthplace of humanity’s earliest ancestors. Famed paleoanthropologist Richard Leakey discovered more specimens in the 1970s at the East African sites of Koobi Fora in Kenya and the paleoanthropological mecca Olduvai Gorge in Tanzania.

Distribution of Homo erectus sites throughout Eurasia and Africa.

The most complete and well-preserved skeletal specimens to date are those of the ‘Turkana Boy’ (featured above in the paleoartist reconstruction). Scientists have discovered a wealth of information from this remarkable specimen. For instance, the shape and size of the pelvis indicate this specimen was a male, and knowing that the wisdom teeth had not erupted and that the size and structure of the other teeth were small, placed his age at less than 10 years old. The young boy would have been a little over 5 feet tall and weighed a little over 100 lbs at the time of his death, nearly 1.6 million years ago. Given how tall the Turkana boy was for his age, he may well have gone on to be around 6 feet tall, although his stature may have been hindered due to the spinal disease he suffered from, as indicated in his vertebrae. Nonetheless, the body size and stature among Homo erectus, like their brain size, varied widely.

How did this species survive for so long?

The most probable reasons Homo erectus survived for so long seem to be a combination of physiology, cultural habits, and cognition. Long legs enabled members of this species to efficiently stride across the landscape, which helped extend the duration of locomotion and how far one could travel, but also perhaps aided in running either to obtain food, chasing down a gazelle, or to escape hostile encounters with dangerous animals or enemies (several other hominins were living on the landscape at the same time).

Culturally, having a reliable and easy-to-manufacture stone tool like the hand axe and the ability to harness fire to cook food, kill dangerous pathogens, and fend off dangerous animals created an extra layer of defense for Homo erectus that would have extended their survival.

Lastly, the cognitive repertoire to develop foresight and planning may have provided this species its greatest evolutionary advantage and breaks down further into three inferred cognitive behaviors: 1) their capacity to care for one another—the sick, the injured, and the elderly, 2) their capacity for risk mitigation, and 3) their ability to mobilize, expand, and wander.    

Capacity to Care

There are documented instances that show Homo erectus likely cared for the old, weak, and infirm. A skull discovered in the Republic of Georgia lacked all its teeth due to age or gum disease, but managed to live for several years after losing them, which suggests it had others around to help process food, given how difficult it would be to chew.

The Turkana Boy mentioned above suffered from spinal impairments (spinal disc herniation and scoliosis), which would have made him have a painful, slow gait and thus made him vulnerable to predators in the East African landscape. Although he only made it into early adolescence, he would have suffered these impairments for years before his death, which suggests he had the assistance of others to survive up to that point. This capacity to care for others would have had lasting repercussions on the long-term evolution of this species and enhanced their survival.

Avoiding Risks

One of my main areas of research interest in graduate school was studying archaeological and anthropological literature on how various groups of people and early humans dealt with various risks living an exclusive hunter-gatherer or foraging existence.

Homo erectus appears to have been the first of its kind to do something many large mammals do not do (leopards are one exception): carry their food away from a kill site to process in a safer location. This might seem like a no-brainer for us today if you live in the African plains, sharing a fallen gazelle with lions and hyenas, but up to around 2 million years ago, early hominins were not apex predators but likely lowly scavengers skittishly picking a few morsels of meat off of a carcass, competing with these other carnivores. The behavior of defending food at a kill site is what is expected from most large mammalian predators, yet Pleistocene hominins performed a more elaborate behavioral ritual that seems to suggest risk mitigation was a part of their cognitive repertoire.

By examining the bones of what Homo erectus was eating, and more importantly, where they were located, we can see a very different pattern of behavior emerging in the archaeological record. Homo erectus would have brought back portions of animal remains to a mentally predetermined and safer location, such as a cave or rock shelter. These havens would have served to mitigate against interfering with other predators and increased their processing times with their stone tools, enabling them to extract the more nutritionally rich marrow found in long bones and brain matter that were housed in the hard braincases. This could have had major evolutionary implications that would have enhanced their diet and hence long-term survival.

Wandering Outside Africa

To me, the capacity to wander beyond one’s immediate environment is a deeply embedded feature of our humanity and played a vital role in our evolution, as I have argued elsewhere. As I reflected in a recent post on our species’ long-term survival,

Had our ancestors stayed in place and located in a small ecological niche we might very well have gone extinct by now in the way of all our previous hominin cousins: the Neanderthals, the Denisovans, and the Australopithecines. By pushing into the unknown and spreading around the globe, we unwittingly ensured a greater probability of existence for our future kin because it forced our ancestors to divide, cope, and adapt to a wide range of earthly climes, thus safeguarding a greater chance of survival during unstable times.

In addition to the other reasons mentioned above, becoming a transcontinental wanderer may be one of the main reasons Homo erectus survived for so long. As noted in the distribution of sites above, Homo erectus gradually made its way across many parts of Africa and Eurasia, leaving Africa nearly the moment it arrived on the scene at 1.9 million years ago. Fossil evidence from Dmanisi, Georgia, shows members of the species reaching western Asia as early as 1.8 million years ago. Spreading about the globe in this manner was akin to not “putting all your eggs in one basket,” something no other hominin species had done up to this point.

We know that cognitively speaking, Homo erectus was not completely comparable to modern humans, but the question of what it was like to be a Homo erectus is a fascinating, albeit difficult, one to entertain. This question alludes to a famous paper written by the American philosopher Thomas Nagel in 1974 titled What Is It Like to Be a Bat? that explored consciousness, its subjectivity, and objectivity.

Similarly, if we could step into the body of a Homo erectus living 1.5 million years ago to peer through its eyes and inhabit its mind, how would we view the world? How similar or different were they to us? Did Homo erectus feel the same restive urge for adventure as we–that itch to move beyond the horizon? Might that be why they were the first to leave Africa? It is still unclear at what point along our human lineage we gained the capacity to wonder about wandering about all those foreign and distant places left unexplored. These are questions we may never be able to know, but they are assuredly worth pondering nonetheless.

Homo erectus Exits the World Stage

Spreading out to explore other opportunities comes with rewards as well as risks, but perhaps staying put in only one location is what ensures a quicker extinction for a species. Homo erectus may have prolonged its existence by spreading out, but extinction comes for us all in the end. The species appears to have gone extinct around 110,000 years ago, with the last vestiges of the species surviving in Indonesia and perhaps evolving into Homo floresiensis, which inhabited the island of Flores up until 50,000 years ago, and became popularly known as “the hobbit” hominin due to its reduced stature.

Homo erectus is often also considered the precursor to our species, first evolving into Homo heidelbergensis sometime during the Middle Pleistocene between 700,000 and 200,000 years ago and then evolving into both Neanderthals and Homo sapiens.

The role Homo erectus played in human evolution has been profound and leaves the world stage with a trail of enigmatic puzzles for us to answer. Why, after such a prolonged time on this planet, inhabiting many different environments, did they go extinct? Were they compelled to wander merely for the next meal, or might they have had the capacity for wanderlust, being drawn to explore for its own sake? This much is clear: a dramatic series of events took place to allow Homo erectus and our own species to become generalists—our bodies, our minds, our diets, our culture—all of these evolved together ever so gradually to enable us to spread far and wide as though our history arcs toward wandering.

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Cheers!

-JSB