Once, it was only our family that seemed special. When stone tools dating back about 1.87 million years were found associated with fossils of two early human species in Tanzania’s Olduvai Gorge, it seemed pretty obvious which of the two species was responsible. To push the point home, the suspected knapper was even named Homo habilis, or ‘handy man’. It left the comforting impression that even so far back in our lineage, early humans cultivated a will and intellect fierce enough to develop stone tools, setting them apart from the remainder of the animal kingdom. The style of tools became known as Oldowan, and as they presented the earliest known examples of stone technology, their appearance ushered in the Lower Palaeolithic era. This, in turn, serves as the threshold of the familiar 19th-century ‘three age system’, based on ancient communities’ mastery of stone, bronze, and iron. Seen in this light, early humans appeared at around the same time as crude stone tools, marking the very beginning of an archaeological framework revolving around technological advances. It was a very neat model. With hindsight, it was a little too neat.
Over the years, Oldowan tool-making has been pushed progressively further back in time, with manufacturing now known to be under way 2.59 million years ago at a site in Ethiopia. This, though, is nothing compared to the bombshell dropped by a French team working at the Lake Turkana site of Lomekwi 3 in Kenya. In 2016, they published the discovery of stone tools dating back 3.3 million years. Not only are these implements getting on for a million years older than the earliest known Oldowan tools, but rather than being associated with our ancestors in the Homo genus, the Lomekwian tools were fashioned by someone else’s hands, most likely a species known as Kenyanthropus platyops. Even this precocious industry is unlikely to be the beginning of the story, though, as – despite the crudity of the Lomekwian implements – there still seems to be a clear understanding of how to make them. The tools do not look like the first ever trial-and-error experiment with stone technology. So, as these discoveries challenge what it even means to be human, the time could not be riper for two British Academy post-doctoral projects tackling aspects of stone-tool use. Tomos Proffitt at UCL is exploring why tools appeared, while Alastair Key at the University of Kent is looking at how they evolved.
‘The Lower Palaeolithic starts with the first modified stone technology,’ explains Alastair, ‘so as the Lomekwian tools had been intentionally changed, and if they were indeed made by Kenyanthropus, it means that the story begins with a species that may not necessarily be directly related to us. It is very exciting. Some species of Homo and australopithecine are on our direct lineage, but it is currently unclear if Kenyanthropus is. They existed around 3.5 million years ago, and while it is likely that our Homo genus evolved from a population of early humans in East Africa at this time, it does not mean that we developed from Kenyanthropus. It’s very hard to draw a direct link between them and us. The Lomekwi 3 discoveries also have an impact on how we view the intellect necessary for an ability to make tools. Kenyanthropus platyops has a brain size that is not considerably bigger than a modern chimpanzee’s. So it’s not necessarily about cranial capacity, it may be more to do with how the brain is wired, which is much trickier to identify and understand. But you clearly didn’t need a huge brain to manufacture the very earliest stone tools.’
‘We can see that Lomekwian and Oldowan tools were being used in various ways. There’s lots of evidence of their use for percussive activities – being used to batter open nuts and marrow cavities, for example. But they were also making flakes, which have relatively sharp edges that could have been used for cutting. There’s an associated site dating back to a similar period as Lomekwi 3 in Ethiopia, where bones potentially bearing cut-marks have been found, suggesting that the hominins responsible were using sharp-edged tools. As you move towards the Oldowan, there’s clear proof that lots of butchery was going on. Relatively smaller flaked tools with lots of sharp edges were being manufactured, most likely for cutting purposes. So you get a combination of battering tools for extracting marrow from bones and perhaps cracking nuts, and implements for extracting meat from carcases, be they sourced through scavenging or hunting. As far as we can tell, the tools are mostly associated with processing food, but may have been used for cutting grasses and working wood as well.’
If the desire to create devices to aid pounding and cutting was common to those wielding both Lomekwian and Oldowan tools, the way in which they were produced was rather different. The Oldowan implements were created using a technique called ‘freehand knapping’, which involves striking the core of material being fashioned into a tool or tools with a hammerstone. The Lomekwian approach was the opposite way around. There, the hammerstone lay motionless on the ground, while the knapper held the core in one or two hands and bashed it against the hammerstone. While the Lomekwian technique created comparatively bigger flakes and cores, these still look like the handiwork of someone who understood the principles of the process. If so, why are the very earliest episodes of stone-tool use proving so elusive? The answer may lie in technology still being used today, just not by humans.
‘One difficulty is nailing down what we would expect the very earliest tool sites to look like’, says Tomos. ‘If you think about making the Oldowan tools, possibly hundreds of flakes would be produced at any given time, eventually creating an archaeological signature of thousands of flakes. But what happened before flaking was developed? Back then, you’d probably be looking at percussive pounding activity aimed at cracking nuts or breaking open bones. So how can you tell the difference between marks on stones caused by intentional behaviour and natural processes that simply knocked them together? It would be very easy to disregard a few marks on a stone as unimportant. My project is looking at ways to establish what the archaeological signature could look like, by studying populations of three species of primate – chimpanzees, macaques, and capuchins – that use stone tools.’
‘Among them, the macaques undertake a whole range of different behaviours, including nut-cracking – which we only found out about last year – and they also crack open oysters and various other seashells. These actions leave very distinctive types of damage on the stone. Interestingly, the macaques use different parts of a stone for breaking open a nut or oyster shell. The tools themselves are also quite diagnostic, so you can identify percussive behaviours based on just the types of stones being used. It’s harder to do that with chimpanzees, because the raw materials they have access to in the wild are not fantastic. There are only two groups that use stone tools, and in both cases it’s only for nut-cracking, which creates far less identifiable damage on the implement. Capuchin stone-tool use was first observed in the wild in the early 2000s. They use them for various tasks, including striking one stone against another to try to pulverise quartzite pebbles for some completely unknown reason. A by-product of that is they unintentionally fracture the stones, producing what we would normally classify as flakes and cores. Capuchins also use stones to dig, so there’s a whole range of different macroscopic and microscopic damage patterns we can associate with particular activities.’
‘I’m finding the macaques more and more interesting. They are mostly island populations, and, as we know, in archaeology islands are often very strange places. On some islands, the macques use stone tools once and then discard them, but on another island – where the ecology and environment are the same – they seem to reuse the same tool over and over again. We have no idea why, but the best bet is that it is due to what you could loosely call some kind of cultural factor. You also get tool-use variation between populations of capuchin monkeys in Brazil. There, variations in behaviour seem to be mostly down to the availability of raw materials, but we can’t dismiss the possibility that there’s also a difference in tool-using traditions between groups. And that’s true of employing stone tools in general. Most populations of chimpanzees, macaques, and capuchins don’t use stone tools at all. So, with these species, it’s not a question of whether they can use them – we know they can – it’s a question of why they do. It was probably the same for early hominins. Just to be clear, though, I’m not suggesting that the early Lomekwian and Oldowan archaeological sites in Africa were made by primates! But I am saying that some of these different types of percussive activities leave signatures that we should be able to detect archaeologically.’
Hands before Handy Man
An ability to use tools is also dependent on another factor that we tend to take for granted today: hands with a bone structure allowing implements to be wielded in an effective manner. Given that the emergence of stone technology essentially depends on raw materials, brain power, and the evolution of sufficiently dexterous hands, when did this third piece of the jigsaw slot into place?
‘There’s a real dilemma in the evolution of hands,’ says Alastair. ‘We have some australopithecine hand bones, but there’s only really one species that has a very well-preserved set. That’s Australopithecus sediba, which lived about 2 million years ago, and has produced almost complete sets of hand bones from one or two individuals. These indicate that while sediba had a transitional hand anatomy, they would still have been capable of producing and manipulating stone tools. So, while their hands were important for climbing activities, they were also able to perform relatively forceful precision grips. As individuals, they were quite small, though, so we don’t know if their grip would have been as strong as ours. When you go further back in time to 3 million years ago, there are some bones that give indications of what hands were capable of, but we can’t see the whole picture. There are signs that Australopithecus afarensis could also perform the sort of grips you’d need, for instance. That seems likely to me, but the fossil record for hand bones is a bit hit and miss.’
‘These are the questions we have to ask now that making stone tools is no longer what sets our lineage apart,’ says Tomos. ‘Jane Goodall blurred the line when she identified that chimpanzees were using stone tools, and now the results from Lomekwi 3 have shown that the division doesn’t exist. The use of tools, the use of technology, is no longer just a human trait. You can’t associate stone-tool use – and now you can’t even associate flake production – with human technology. It’s become a hominin technology, and possibly even a primate technology. We have to start looking at the possibility that there have been all sorts of inventions and losses of different types of stone-tool use over time. The Oldowan and then the more sophisticated Acheulean tools that we can securely identify with Homo handiwork are just the branch of the technology that carried on through. There’s an increasing body of evidence suggesting earlier species were using a type of stone tools. After all, it gives such a significant advantage over not using technology, and there’s no reason why it shouldn’t have been developed by multiple species.’
Chips off the old block
But if we can no longer claim that early humans presided over the dawn of technology, it is at least possible to see how the Homo genus made its presence felt as tools became increasingly sophisticated. Despite the differences in technique, the Lomekwian and Oldowan tools are relatively simple to create. With the Lomekwian implements, in particular, it really is essentially a case of hitting two stones together. A degree of understanding is still required, and there is an appreciation that striking the stone at a different angle had an impact on flake size and shape. The Oldowan tools show a higher level of variety, and there are cores displaying different patterns of flakes, which indicates varying knapping strategies were in play, but all of this is refining rather than revolutionising the basic level of understanding needed for the Lomekwian. To put it another way, the fundamental technology remained essentially unchanged.
The step change came with the arrival of Acheulean tools about 1.76 million years ago. These represent a quantum leap from detaching one flake after another from a core, possibly in a relatively random manner, to artisans working towards a fixed idea of what the finished implement would look like. From the start of the process, the knapper would hold in their mind an image of the hand-axe, cleaver, or pick that they wanted, and work progressively towards that end. This greater manufacturing complexity appears at around the same time as Homo erectus and Homo ergaster in Africa. These had much larger cranial capacities than earlier hominins. So this increase in cognitive ability may well have paid off with the ability to produce tools that can only be fashioned with the assistance of sustained abstract thought. Here, then, is an innovation that seems unique to the later members of our family: an ability to work doggedly towards an imagined goal. It was a capability that paid dividends. Acheulean tools are found around the world, because this technology gave our ancestors enough of an edge to spread out from Africa across the globe.
FURTHER INFORMATION Tomos Proffitt and Alastair Key hold British Academy post-doctoral fellowships. To find out more, a related Open Access academic article can be found here: www.nature.com/articles/nature20112