When Did Humans Start Accumulating Social Knowledge?
Study Reveals Early Evidence of Human Cultural Transmission 600,000 Years Ago
A key aspect of human evolutionary success is our ability to build on past knowledge. Unlike other species, humans don't have to learn how to do things from scratch. Our societies have developed various methods, from formal education to online tutorials, to pass on what others have learned. This cultural transmission makes learning more efficient and fosters innovation, allowing us to experiment and improve upon existing technologies and methods.
While some of our closest relatives, like chimps and bonobos, learn from each other, they don't engage in the iterative process of improvement that characterizes human culture. They lack what is known as cumulative culture, where new technologies are built upon the knowledge of previous generations. The question then arises: when did humans develop this ability?
A recent analysis1 of stone toolmaking by researchers Jonathan Paige and Charles Perreault suggests that this capability is relatively recent, dating back to just 600,000 years ago. This period coincides with the divergence of our ancestors and the Neanderthals, marking a significant milestone in human evolution.
Accumulating Culture
Human technology is a testament to cumulative culture. If you're reading this on a mobile device, you're benefiting from a long history of technological advancements. But tracing the origins of this iterative process in our ancient history is challenging. For millions of years, human tools lacked the clear building blocks that signify cumulative culture, making it difficult to identify when this capability first emerged.
Paige and Perreault took a straightforward approach to this problem, focusing on stone tools, which are well-preserved across our species' history. They argue that the sophistication of these tools can provide insights into the development of cumulative culture.
"As new knapping techniques are discovered, the frontiers of the possible design space expand," they explain. "These more complex technologies are also more difficult to discover, master, and teach."
The key shift, according to the researchers, is from simply teaching the next generation to make the same tools to using that knowledge as a foundation to build something new. Paige and Perreault argue that the complexity of toolmaking provides a measure of when cultural accumulation started:
"Generations of improvements, modifications, and lucky errors can generate technologies and know-how well beyond what a single naive individual could invent independently within their lifetime."
Measuring Complexity
The challenge then is to measure the complexity of ancient tools and determine when it crosses the threshold that a "single, naive individual" couldn't develop on their own. Paige and Perreault focus on what they term a "procedural unit," defined as "discrete, mutually exclusive manufacturing steps that can be chained together." The more procedural units required to make a tool, the more complex the manufacturing process is.
The earliest stone tools involved just three of the 33 total procedural units identified by the researchers. In contrast, the most sophisticated tools from the past 10,000 years required 19 procedural units. Paige and Perreault set a cutoff of six procedural units as the threshold for cumulative culture, based on examples from primate relatives, unskilled humans, and random rock chipping.
Examining actual tools, they identified three distinct periods. The first, from 3.3 million to 1.8 million years ago, is characterized by simple tools requiring four procedural units or less. The second, from 1.8 million to 600,000 years ago, saw tools requiring between four and seven procedural units, sitting right at the complexity threshold. It is only around 600,000 years ago that tool complexity consistently exceeded this baseline, indicating the presence of cumulative culture.
The Significance of 600,000 Years Ago
The timing of this increase in complexity is notable, as it aligns with the divergence of Neanderthals and the ancestors of modern humans. At this point, the tools produced by these two branches of humanity were roughly equal in sophistication.
Paige and Perreault's findings suggest that the ability to accumulate and build upon social knowledge emerged around 600,000 years ago. This development likely played a crucial role in the evolutionary success of both modern humans and Neanderthals.
Implications and Future Research
While stone tools provide a valuable window into the past, they are just one aspect of human technology. Other manufactured technologies, which are not preserved, may also reflect the presence of cumulative culture. The long periods of apparent stasis in technological development could be due to the need for both technological and biological evolution, or simply the difficulty of solving certain technological problems.
Regardless of the precise details, it is clear that by about 100,000 years ago, the barriers to cumulative culture had been removed, leading to a dramatic increase in the sophistication of manufacturing. This period marks a critical point in human evolution, showcasing our capacity for innovation and cultural transmission.
Understanding when and how cumulative culture developed helps us appreciate the complex interplay between biology, technology, and social learning that has shaped our species. As researchers continue to investigate these questions, we will gain deeper insights into the origins of human cultural and technological achievements.
Paige, J., & Perreault, C. (2024). 3.3 million years of stone tool complexity suggests that cumulative culture began during the Middle Pleistocene. Proceedings of the National Academy of Sciences of the United States of America, 121(26). https://doi.org/10.1073/pnas.2319175121