When did our hominid ancestors first start using tools? This is a fascinating question of human paleontology, and it is also difficult to answer definitively. There are two basic reasons for this difficulty. The first is generic to all paleontology – our knowledge of when something emerged is dependent upon the oldest specimen. But the oldest specimen is likely not the very first emergence, so dates are frequently being pushed back when yet older specimens are discovered. Often scientists will say that something is “at least” a certain age old, knowing it could be older.

Tool uses specifically, however, has another challenge – we can only really know about tools that survive and are recognizable in the record. If early hominids were using wooden tools, for example, it would be very difficult to know this. If they were using unmodified stones this would also be difficult. We could potentially infer such use if the results were visible in the fossil record, such as marks on the bones of prey, but that can be difficult.

So when we talk about the earliest evidence for tool use in our ancestors we are talking about crafted stone tools. The oldest known stone tools date to 3.3 million years ago, at the Lomekwi 3 site in Kenya. At this time there were Australopithecines around but not yet any members of the genus Homo. H. habilis and H. rudolfensis date from 2.8-2.75 million years ago.

However, the evidence suggests that this early stone tool use was sporadic, meaning that a population may have used stone tools for a time but then the knowledge was lost and was then rediscovered later. But again – was early stone tool use sporadic or is just our evidence sporadic? Scientists are constantly just trying to infer the best explanation from the evidence we have, but frequently have to modify this inference as new evidence comes in. There are often competing hypotheses – different ways to put all the evidence together into a consistent and logical narrative. One such narrative was that early hominids sporadically used tool use but did not have a continuous technological culture. This did not emerge until about 2.4-2.2 million years ago, getting closer to the emergence of H. erectus. The belief was that it was larger-brained Homo species that first developed continuous stone tool technology, partly because they required it to process meat and feed their hungry larger brains.

You probably know where this story is going – now paleontologists have documented evidence of continuous stone tool culture spanning 300,000 years going back to 2.75 million years ago, about 400,000 years earlier than previously known. This was not just evidence of stone tools, but of a technological culture demonstrating consistent and sophisticated techniques of tool construction. This is also in Kenya, and the likely tool-makers were H. habilis, but we cannot rule out that Australopithecines were making tools also.

This tool culture is known as Oldowan, named after the first specimens from Olduvai Gorge in Tanzania, and spanning from 2.75 to 1.7 million years ago. It is amazing to imagine a technology lasting for one million years, being passed down continuously from one generation to the next, even across difference evolved species. The technology involves finding optimal stones for use, which means that the culture required some geological knowledge – where to find and how to identify the best stones. They also needed to develop techniques and skills for flaking these stones to creature sharp edges, and shaping them for different uses.

This technology was likely critical for the survival of the species that used it, allowing them greater access to a variety of food. This would have allowed them to adapt to the rapidly changing environment of Africa at this time. It also represents in a basic way the utility of having a large brain – it allows populations to adapt culturally to their environment, rather than having to adapt physically through evolution. Cultural evolution is more rapid than physical evolution, and modern human civilization shows how fast and profound that adaptation can be. What we are seeing with the Oldowan tool kit is a very early example of cultural/technological adaptation.

There is also a “chicken and egg” lesson here as well. Paleontologists often struggle to infer the order in which things emerged. The classic example in human evolution was the early assumption by scientists that our ancestors evolved large brains first followed by bipedalism and a more modern body structure. So they imagined our ancestors to be large-brained apes. In reality, the opposite was true. Our ancestors were small-brained (relatively speaking) bipeds.

In this case, our ancestors needed stone tools to secure enough food to feed a large brain, so they imagined that continuous stone tool use did not exist until we have larger brains. But now we are finding the opposite was true – continuous stone tool use emerged among our relatively smaller brained ancestors. This actually makes more sense to me – stone tool use allowed for larger brains to evolve. The same is likely true of hunting and cooking food with fire, which also greatly add to our access to nutrients. There was likely a feedback loop here – larger brains allow for more sophisticated behavior which allows for larger brains. But it looks like the sophisticated behavior likely came first, and our belief otherwise is likely just a bias toward thinking of our ancestors as being more primitive than they were and therefore underestimating them.