Why Did Human Intelligence Rapidly Expand Between 800,000 and 200,000 Years Ago? — Here’s What Scientists Suggest

Humans are one of the smartest creatures in the animal kingdom. We have become a truly intelligent species that dominates and rules the planet. We could shape our world to fit around us, instead of the other way around. However, it wasn’t always like this.

7 to 6 million years ago, our lineage was only beginning to stand and walk upright. Then, around 2 to 1 million years ago, we developed even more traits that define what it means to be a human, such as a more refined bipedalism, loss of fur, changes in skin color, the ability to run long distances, the development of stone tools, and more.

But one of the most significant traits that resulted from all of those years of adaptation was the growth of human intelligence. However, between 800,000 and 200,000 years ago, something happened, as the already increasing intelligence of humans rapidly expanded even more. What could’ve caused this event, and how did it affect our evolution to become who we are today? Let’s dive deep into some of the best theories in this article.

Environmental Challenges and Adaptive Pressure

One of the leading theories why our intelligence expanded rapidly between 800,000 to 200,000 years ago was because of environmental pressures and changes. During this timeline, Africa and the rest of the world were suffering from fluctuating climates, glacial cycles, droughts, the receding of forests, and the expansion of savanna or open areas.

It means that the hominins during those times, such as Homo erectus, Homo heidelbergensis, Neanderthals, and at the later stages, Homo sapiens, needed to adapt to an ever-changing world to survive. Their habitats, including food and water sources, were depleted in some areas, triggering migration to find more abundant and livable places.

But how does this series of events make our brains grow? Well, the theory states that this harsh environment favored those who are smarter. In other words, the individuals who had enough cognition to find new food sources, successfully migrate to a new habitat, and solve everyday challenges were the ones who are most likely to survive and pass on their genes.

Over time, it resulted in our brains growing in size, and human intelligence along with it. Although having bigger brains does not automatically make a species smarter, in the case of Homo sapiens, it allowed us to obtain more cognitive abilities. We then utilized it to refine and develop the skills and knowledge that were already passed on to us, such as the use of stone tools, complex social structures, and cultural traditions.

Read more: PubMed Central

Diet, Nutrition, and Energy for Big Brains

The Evolution of Intelligence: 5 Key Breakthroughs

The brain is one of the most metabolically expensive organs both to grow and to maintain. In other words, for it to grow together with our sheer intelligence, first it must be beneficial to our survival, and second, we should have achieved enough of the prerequisites necessary for its expansion.

This leads us to another theory why our intelligence grew rapidly between 800,000 and 200,000 years ago, which is the changes in our diet, nutrition, and lifestyle. During this period, the Acheulean industry’s stone tools became widespread. Before it, the Oldowan stone tools, about 2.6 million years ago, were used, which are characterized by simple choppers and flakes.

However, during the Acheulean industry and towards its late stages, until the post-Acheulean era, different weapons that were a lot better for hunting were developed. This included thrusting spears, throwing or projectile spears, and bone-tipped weapons. This meant that previously uncommon and difficult-to-obtain food sources, such as meat from bigger creatures like mammoths and bison, were now much more attainable.

Additionally, humans have progressed with their control of fire and started cooking, which gradually changed our anatomy, specifically how efficient it could be. These features, together with more calorie-dense and nutritious food sources, allowed our body to make more energy for the growth and development of the brain and our intelligence along with it.

Social Complexity, Cooperation, and the Social Brain

Another idea why our intelligence grew rapidly during this timeline is the social brain hypothesis. It states a positive feedback loop where our brains grew as more people became included in our group, possibly due to the rise of our abilities to support more people, because of better tools and resource acquisition strategies. Then an increase in our population triggers even further growth of the brain and our intelligence.

This is because humans and most hominins are social creatures that need each other in order to survive. This meant that inside the group, one would need to navigate the social complexities, including knowing who is a friend or a foe and how to cooperate with everyone. All of these required mental and cognitive sophistication, and this pressure from a growing population group could have influenced the increase in our intelligence.

Read more: Smithsonian Human Origins

Culture, Tool Use, Language, and Cumulative Innovation

Why We Got Smart - The Story of the Hominid Brain ~ with ZACHARY COFRAN

Brains do not just grow if it is not utilized. The increase in our intelligence is most likely because of what we did during the period 800,000 and 200,000 years ago. One of the theories is the development of cumulative culture, where hominins developed to be smart enough to be able to pass and teach the knowledge and skills they have acquired during their existence.

This would mean that the next generation would not need to start from scratch. In other words, every ability could be enhanced and refined even further. For example, a cumulative culture applied to tool usage would make hunting strategies better over time, and with it, an increase in a nutritional and calorie-dense diet. This would therefore allow our brains to develop to be bigger and have more cognition.

Additionally, this phenomena have a powerful, self-reinforcing feature built into it where new generations that became smarter because of the past adaptations, like changes to diet, lifestyle, and other factors, could invent new technologies or survival strategies that could make those diets and lifestyles even better, triggering a loop where each improvement sets the stage for even more significant advancements at a faster pace.

Author's Final Thoughts

The increase in the intelligence of humans was not just because of one factor. It is likely that all of these theories and hypotheses discussed were all part of it in some type of way.

The environmental pressures could have naturally selected the smarter hominins. The development of a better toolset could have resulted in more efficient hunting strategies and increased the nutritional value of our diet. The growing population of the group could have added even more demand for our brains, and lastly, the cumulative culture of hominins could have all made the adaptations and advancements progress at a faster rate.

The combinations of these factors may be what led our lineage to grow smarter and smarter. Our brains grew in size, but it wasn’t just for show. It was a result of the relentless pressure of survival, which forced and enabled our ancestors to innovate, become more creative, navigate complex social dynamics, and adapt in an ever-changing world.

Read next: How Did the Invention of Stone Tools Over 2.6 Million Years Ago Transform Early Human Life? — Here’s What Researchers Found Out

References & Further Reading

Maslin, M. A., Brierley, C. M., Milner, A. M., Shultz, S.,Trauth, M. H., & Wilson, K. E. (2014). East African climate pulses and early human evolution. Quaternary Science Reviews. https://doi.org/10.1016/j.quascirev.2014.06.012

Aiello, L. C., & Wheeler, P. (1995). The expensive-tissue hypothesis: The brain and the digestive system in human and primate evolution. Current Anthropology. https://doi.org/10.1086/204350

Berna, F., Goldberg, P., Horwitz, L. K., Brink, J., Holt, S., Bamford, M., & Chazan, M. (2012). Microstratigraphic evidence of in situ fire in the Acheulean strata of Wonderwerk Cave, Northern Cape province, South Africa. Proceedings of the National Academy of Sciences. https://doi.org/10.1073/pnas.1117620109

Wrangham, R. (2017). Control of fire in the Paleolithic: Evaluating the cooking hypothesis. Current Anthropology. https://doi.org/10.1086/692113

Rightmire, G. P. (2004). Brain size and encephalization in early to Mid-Pleistocene Homo. American Journal of Physical Anthropology. https://doi.org/10.1002/ajpa.10346

Neubauer, S., Hublin, J.-J., & Gunz, P. (2018). The evolution of modern human brain shape. Science Advances. https://doi.org/10.1126/sciadv.aao5961