There are few things more irritating in everyday life than getting something stuck between your teeth. Thankfully, we can reach for a toothpick 鈥� and it seems our ancient ancestors did the same. In fact, a fragment of a 1.2-million-year-old toothpick is perhaps the earliest direct evidence we have of hominins using plants as tools.
Our ancient ancestors probably made frequent use of implements made from plants. But finding evidence of this is extremely tough because botanical materials are so quick to rot away. This means the archaeological record of human tool use is deeply skewed towards the much hardier stone.
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All this suggests that the origins of human technology could have been profoundly misunderstood.
Stone Age
The conventional view is it all started with the first stone tools and the dawn of the Stone Age over 3 million years ago. But what if, even before that, there was a botanical age, one based on woodworking and weaving of plant materials? For some researchers, it is absurd not to think that plants would be part of the story. 鈥淧erishable material culture is an essential element in our evolutionary past,鈥� says Linda Hurcombe at the University of Exeter in the UK.
Now, we are finally getting a clearer view of this lost age. New techniques are making it possible to find traces of plant-based tools that would otherwise have been missed. And by studying the way modern primates use plants, researchers are getting clues as to how traces of the human Botanic Age might be preserved in the fossil record. All in all, it鈥檚 a shift that might lead to a radical rethink of the origins of human technology.
There is an undeniable logic behind the burgeoning idea of a Botanic Age. The use of tools made from plants is universal across non-industrialised societies and in our closest ape relatives, so it seems inconceivable that ancient hominins . That is certainly Hurcombe鈥檚 view. In fact, she and other researchers like her think that implements made from organic materials make up the 鈥渕issing majority鈥� of artefacts upon which the foundations of the Stone Age probably rest. A small but growing number of these researchers are dedicating themselves to finding evidence of this undiscovered era of human evolution.
Archaeology
So far, the oldest direct evidence we have of this period is that fragment of ancient toothpick. This was discovered in 2016 when at the University of Glasgow, UK, and her colleagues found a in the fossilised tooth plaque of a 1.2-million-year-old hominin from Atapuerca, Spain. The fragment was next to characteristic straight scratches on the teeth, called interproximal grooves, which scientists believe indicate .
But it is likely that plant-based tools and implements were in use far earlier than this. Indeed, in the 1970s, the feminist anthropologists and suggested that containers such as . They were pushing back against the 鈥渕an the hunter鈥� dogma that placed men and their activities at the forefront of hominin evolution. 鈥淚t wasn鈥檛 really picked up on鈥� but it was a vastly important insight,鈥� says at Florida State University.
Their idea was that having a way of securely carrying and storing gathered food and water would have been fundamental for hominins from very early on. This hypothesis extends to something else that would have been equally important to carry: babies. It is thought that this need stemmed from a uniquely human transition that started more than 6 million years ago, well before the Stone Age 鈥� the move to walking on two legs.
With the transition to bipedal walking came a corresponding shift in the position of the big toe that reduced our ability to grip with our feet. This, combined with losing most of our body hair, meant that babies could no longer cling onto their mothers like other primates do 鈥� and dropping your baby is a pretty big setback, not least from an evolutionary perspective.
Falk, who is writing a book on humanity鈥檚 Botanic Age, says that baby slings were a clear solution to this problem and that 鈥渂askets on the hips鈥�, as she calls them, may have been the first human-modified plant tools. 鈥淓ven just a strap of vine or grass could have been the first slings,鈥� she says. For Falk, this would have been 鈥渁n obvious light-bulb moment鈥� for early hominins. This idea is supported by ethnographic evidence showing that , with caregivers using organic materials such as plants, animal skins and fabrics to secure infants to their chests or backs.
The problem is that there is no direct archaeological evidence for this early technology, and there may never be. 鈥淚t鈥檚 tantalising, but until somebody comes up with some other way to get at that question, I don鈥檛 know what we can do with it,鈥� says at Emory University in Atlanta, Georgia. We aren鈥檛 going to find something used as a baby sling by hominins that far back in time, he says.
Ancient hominins must have started to use containers at some point, but even if these survived, how could you prove that prehistoric people used, say, a leaf as a cup, like modern-day chimps do? 鈥淎rchaeologically, we have this roof, where we have really clear evidence for containers only after about 100,000 years ago,鈥� says at Griffith University in Australia. This came from at Blombos cave in South Africa, where a liquid ochre paste was produced and stored in abalone shells. All traces of the containers that must have been used before this time have disappeared.
Oldest wooden artefact
But, very occasionally, botanical artefacts are discovered. Currently, the oldest wooden artefact modified by hominins seems to be an approximately unearthed in the 1990s in northern Israel. But this is far from clear-cut, and at the University of Reading, UK, says the find needs to be reassessed using modern techniques to double-check that it is indeed an early example of woodworking. That makes last year鈥檚 discovery of 476,000-year-old notched logs at Kalambo Falls, Zambia, perhaps used as part of wooden structures, the earliest unequivocally hominin-modified botanical artefact.
There is then a gap of a few tens of thousands of years before the next evidence appears: , UK, from 400,000 years ago, four other wooden tools from Kalambo Falls including a digging stick and a wedge from 324,000-390,000 years ago and the found in Germany, which date back 300,000 years.
At the moment, researchers are relying on these lucky finds to piece together humanity鈥檚 Botanic Age. But at Kenyon College in Ohio says that 鈥渋f we鈥檙e going to make any more headway in palaeolithic archaeology, we have to find a way to detect those perishable materials鈥�. To do this, he says, we need to get out our microscopes.
In 2016, Hardy was handed a stone tool with a little white fleck on its underside that had been dug up from a Neanderthal site in south-eastern France. He placed it in a vacuum chamber and fired up a scanning electron microscope. Incredibly, Hardy could discern plant fibres that were clearly the remnants of an intricately made 50,000-year-old three-ply twisted thread. He could even identify the long structure of the cells in enough detail to say the .
Hardy thinks the cord was saved by being beneath the stone tool it was found attached to. Although the twisted fibre could be completely unrelated to the tool, the stone stopped the decay process by acting as a protective barrier from groundwater. Other plant residues can also stick to stone for millennia, such as microscopic silica particles called phytoliths. The oldest evidence of woodworking tools comes from phytolith remains called hand axes from Tanzania, which suggest they were used for chopping wood, perhaps from a type of acacia.
But Hardy says that many researchers who study stone tool finds may be inadvertently destroying these crucial botanical residues. When looking at the fine marks left behind from repeated activity, known as use-wear analysis, researchers often scrub away anything on the stone鈥檚 surface to get a more fine-grained image of the damage. 鈥淥nce we wash it, we lose that evidence,鈥� says Hardy. 鈥淭here鈥檚 likely to be so much more stuff out there. If you don鈥檛 look for it, you don鈥檛 know.鈥�
Was there a technological Botanic Age before the dawn of the Stone Age?
This isn鈥檛 to say that use-wear analysis isn鈥檛 a valuable source of indirect evidence for prehistoric plant processing. In fact, this is how Hermine Xhauflair at the University of the Philippines Diliman and her colleagues discovered that from Tabon cave in the Philippines had been used to strip plants. But 鈥渢he devil鈥檚 in the details with all of that kind of research鈥�, says Stout, and often the evidence is debatable as to whether the particular pattern of modification was caused by a certain behaviour. 鈥淚t鈥檚 easier to find something if you know what it looks like,鈥� he adds.
To do this, researchers are turning to our living, tool-using, primate cousins for inspiration. For instance, at the University of Oxford is looking specifically at chimp tech that early hominins are known to have also used, and is tracking the signatures they leave behind. This new strand of primate archaeology, what she calls the 鈥渁rchaeology of the perishable鈥�, is focused on establishing the use-wear patterns left when making and using plant tools.
Pascual-Garrido鈥檚 research focuses on chimpanzees using wooden probes to fish for termites, which suggests hominins also used. Currently, the oldest evidence for this behaviour comes from research from 2001 showing that Paranthropus, an ancient hominin that lived in southern Africa, used bones to dig into termite mounds to obtain a protein-rich meal . Although this isn鈥檛 a botanical find, delicate probes made from plants are much less likely to preserve over such long periods.
So, rather than looking for the sticks themselves, archaeologists may have more luck keeping an eye out for fossilised versions of where the tools were sourced from. Pascual-Garrido is trying to form a library of the scars on the trees that form when chimps make their tools, for archaeologists to compare finds with.
Learning from primates
Between 2014 and 2016, she visited three Tanzanian chimpanzee communities and discovered their recently used termite-fishing spots. Turning her back on the mounds, she inspected the surrounding trees. She found , with the outer bark of thin branches having a 60 to 80-centimetre-long and 0.5-centimetre-wide strip peeled off, as well as incisor bite marks from where the chimp used its teeth to remove the strip for use as a probe.
These bark scars were still identifiable after three years, showing the lasting nature of these signatures. That is critical because it might take some time before the living tree becomes part of the archaeological record. , who collaborates with Pascual-Garrido at the University of Oxford, says that tracking how these scars change over time is key to being able to find any preserved archaeological traces. This involves following how the colour of the scars transforms as the bark heals and watching how the tree then regenerates itself.
Pascual-Garrido has spent the past two years back with the Tanzanian chimps and says her early findings are showing that the apes 鈥渓eave characteristic traces in the environment that can be identified for much longer than we currently think鈥�. This gets us one step closer to being able to identify botanical evidence of termite-fishing in the early human record.
Meanwhile, another group of researchers is hunting for a different type of plant tech: pounding tools. Currently, the are a selection of chunky, 3.3-million-year-old stones called cores, used for pounding open hard resources, perhaps nuts or bones. Modern-day chimpanzees in Ta茂 National Park, Ivory Coast, use these kinds of bulky stones to crack nuts, but, crucially, they also use wooden hammers, according to the nuts鈥� properties. at the Max Planck Institute for Evolutionary Anthropology in Germany thinks it is reasonable to speculate that early hominins would have also used wooden hammers and is leading a project that is searching for these early wooden pounding tools. 鈥淢ost people doubt that they can be found in the archaeological record, 鈥� says Luncz. 鈥淲e鈥檙e a small crowd who believe they can.鈥�
By looking at chimps鈥� discarded wooden hammers, Luncz and her team found that this repeated percussive activity leaves . The grain on the surface becomes much less horizontal at the points of impact and the wood forms obvious pits. Critically, they discovered there is also irreversible damage to the internal cell wall structures, which become compressed in a highly diagnostic way. Internal cellular anatomy is , so these findings could help us spot evidence of pounding in the ancient human record. That is what Luncz and her colleagues are working on now.
Although rare, that are over a million years old have been found at African hominin sites. Luncz鈥檚 team is looking at pieces of fossil wood from in northern Kenya, a site known as 鈥渢he cradle of mankind鈥�, where many hominin species lived from around . She says she is hopeful that by applying the results of the chimp research to these remains, she and her team will be able to identify pounding in the archaeological record.
All of these efforts mean there has been steady, if gradual, progress in revealing humanity鈥檚 possible pre-Stone Age botanical period. From this, we may one day learn that species we had previously assumed weren鈥檛 tool users, because their fossil remains hadn鈥檛 been found with any stone tools, were actually tech savvy.
Hunting for traces of humanity鈥檚 earliest botanical possessions is certainly far more challenging than unearthing stone artefacts, but it has the potential to shine a completely new light on the lives of our ancient ancestors. 鈥淚t will open up some really interesting questions,鈥� says Almeida-Warren.
