(CN) — Every advancement relies on what came before. Isaac Newton knew this when he wrote, "If I have seen further, it is by standing on the shoulders of giants." A new study published in Proceedings of the National Academy of Sciences suggests that the trend of passing down and improving upon knowledge dates back hundreds of thousands of years — and that the practice is a sign humanity's primitive ancestors were developing their own cultures.
The study, co-authored by the University of Missouri-Columbia's Jonathan Paige and Arizona State University's Charles Perreault, analyzes stone tools from across multiple epochs, starting as far back as 3.3 million years ago.
They determined how many steps it would take to manufacture those tools; an implement that requires more steps is more advanced. By charting how the number of steps changed over time, the researchers charted the path of advancement — and the social development needed to pass those techniques on.
Researchers found that the earliest identified tools took between two and four steps to make — and it stayed that way for about 1.5 million years, when tools showed significant signs of improvement. That improvement came in the form of so-called "Acheulean" tools, which took between four and seven steps to construct.
Even after the invention of the Acheulean hand axe, improvements were slow. But somewhere around 600,000 years ago, during what's known as the Middle Pleistocene Epoch, something changed.
You're not supposed to reinvent the wheel, but ancient hominins may have had to reinvent the hand axe multiple times from scratch.
But during the Middle Pleistocene, which spanned from 770,000 years ago until 129,000 years ago, our ancestors started creating tools that were more complex than what one hominin could have discovered on their own.
Around this time, hominins developed a method called the "Levallois technique." The method involves shaving a piece of flint until it has a tortoise-like shape, then hitting it in a way that would splinter off a sharp flake the size of the toolmaker's choosing. This flake could be used as a scraper, a knife or even the end of a spear.
Other improvements that showed up during this period include using a so-called "soft hammer" made of wood or antler to expertly carve a stone, and retouching stone tools with a technique called "pressure flaking."
Researchers argue that to develop and continue using these advanced techniques, early hominins must have developed what they call a "cumulative culture." This means they started to pass on techniques they learned to the next generation, who would take this knowledge and improve upon it.
The development of cumulative culture may have happened before the divergence between Neanderthals and modern humans. The study's authors argue the rise of social learning coincided with the evolution of heavier brain mass and longer lifespans in humans.
More-complicated stone tools might not be the first instance of cumulative culture — the researchers say humans' prehistoric ancestors could have developed foraging techniques or other social behaviors sometime before they taught each other better ways to make implements. While it's all but impossible to find archeological evidence of that kind of culture, tool improvements are the best way available to measure the development of societies.
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