Thanks to CuriosityStream for supporting PBS
Digital Studios About 2 and a half million years ago, in the
Middle Awash Valley of Ethiopia, one of our ancient human ancestors -- or maybe a group
of them -- crouched over a carcass of an antelope on the shore of a lake. One of these hominins took a sharp stone flake
and sliced into the flesh on the inside of the jaw, grazing the bone and leaving three
cut-marks. These ancestors were after the meaty tongue
of the animal, and in trying to remove it, they left traces of this remarkable moment:
the use of a tool by a human ancestor. They also left behind the technology itself,
in the form of a few scattered stone tools. This site, now known as Bouri, is one of the
earliest confirmed locations where a human ancestor or relative permanently modified
some part of the environment around them to suit their needs - chipping raw stone into
a tool. In the broadest sense, this is what technology
is: making tools and using them to interact with the world around you. These simple stone flakes and the cores of
rock they were struck from are what anthropologists call Oldowan tools - named for Olduvai Gorge
in Tanzania, where they were found. And while these tools don’t seem like much
when you compare them to the screen you’re watching right now, their creation represents
a pivotal moment in the origin of technology and in the evolution of our lineage. This is when our ancestors first started to
make the world around them fit their needs. But what they didn’t know at the time was
that this use of technology would change them, too. Because the fact is, the use of tools has
not only enabled our lineage to take over the world, it has also shaped our very biology,
from our brains to our skeletons. Of course, hominins didn’t invent the use
of tools. The first of our ancestors to make and use
technologies like the Oldowan tools were just expanding on the behavior of our primate ancestors
and cousins. Chimpanzees, our closest living relatives,
and capuchin monkeys, a much more distant branch on our family tree, make and use tools
to get at choice foods, like termites and nuts. But hominins - the branch of our family tree
that’s more closely related to us than to chimps and bonobos - took things a step further. They created permanent tools out of carefully
chosen materials that were then sometimes carried around and re-used. And the Oldowan instruments weren’t the
first tools that hominins ever made. In 2011, anthropologists working in West Turkana,
Kenya, found evidence of a different type of stone tool that pre-dates the Oldowan by
around 700,000 years. These tools are even simpler than Oldowan
choppers and flakes, they’re called Lomekwian tools, after the site of Lomekwi
where they were found. And they’re dated to 3.3 million years ago. They also seem to have been made in a different
way. Oldowan tools were made by hominins holding
rocks in both hands and striking them together. But Lomekwian tools seem to have been made
by holding only one rock and striking it against another that was sitting on a flat base, or
against the flat base itself, to break it and create a sharp edge. And it seems likely that the tool-makers at
Lomekwi were doing this for the same reasons that the hominins at Bouri were: to try to
get hidden foods, like bone marrow or the insides of hard-shelled nuts. But we don’t know for sure, because, unlike
at Bouri, the Lomekwi hominins didn’t leave behind butchered bones . Still, in both cases, these tools allowed
our early ancestors to get at more nutritious foods more often. And this might’ve kickstarted a feedback
loop that affected our bodies forever -- starting with our brains. We don’t know for sure who the tool-makers
at Lomekwi and Bouri were, but they were most likely australopithecines, members of that early
and diverse group of hominins found mostly in eastern and southern Africa. And members of this genus typically had smaller
brains and smaller bodies than hominins that followed them: the early members of our
genus Homo, who appeared on the scene in eastern Africa around 2.4 million years ago. These early members of our genus probably
used Oldowan tools, too, like the hominins at Bouri. And the ancestors that used these tools seemed
to do pretty well for themselves. For example, the earliest known site with
clear evidence of long-term and consistent meat-eating is an Oldowan site called Kanjera
South in Kenya, dated to about 2 million years ago. Over a period of hundreds
to thousands of years the hominins there acquired and butchered
many small ungulates, like gazelles, and occasionally larger antelope,. And all that meat and marrow is really high
in calories, compared to things like fruits and tubers. So regular access to all those calories might’ve
paved the way for our large brains and, in turn, further technological innovation. Now the next phase in the history of our tool
use is where things get even more interesting, and more complicated. Because, this is where we start to find tools
outside of Africa … but we’re not sure who made them. The traditional story from this point in the
anthropological record is that, a little less than 2 million years ago, we see both a new
hominin and a new, more complicated type of tool emerge. This is when Homo erectus makes its first
appearance in Africa, about 1.9 million years ago. And this species had a larger brain, larger
body, and smaller teeth compared to earlier hominins - all hallmarks of a higher quality
diet. Brains are especially expensive, when it comes
to how many calories they require to develop and to maintain. And so are larger, more muscular bodies. So it was thought that this might explain
why a new, more sophisticated toolkit started to appear regularly around 1.7 million years
ago. These were large cutting tools, including
things like hand-axes, which are made by flaking hand-sized rocks to a point on both sides,
with a rounded end for gripping. These newer more complex instruments became
known as the Acheulean toolkit. And until very recently, those tools were
thought to have first been made by African members of Homo erectus, and this development
was seen as the next pivotal step in our ancestors’ use of tools. But new finds from China might make this story
much more complicated. In 2018, researchers published their discovery
of Acheulean tools from the site of Shangchen, which were dated to 2.1 million years old. That date pushes back the appearance of Acheulean
technology some 400,000 years. And it’s also 300,000 years before the time
when the earliest hominins were thought to have made it out of Africa. The earliest known fossils of human ancestors
that we’ve found outside of Africa belong to a population of Homo erectus, found at
a site called Dmanisi in the Republic of Georgia, dated to 1.8 million years ago. But who made the tools found in China is still
unknown. The general consensus is that it was probably
Homo erectus. Because, fossils of Homo erectus have been
found at another site in China that are 1.7 million years old, so we know they made it
there at some point. But other researchers have suggested that
maybe it was an earlier member of genus Homo that made the tools, like maybe Homo habilis. It’ll take more research to figure out what
exactly is going on here, but that’s part of what makes paleoanthropology so interesting:
New discoveries are made all the time. And all of these technological innovations
- from the very simplest to the more complex stone tools - were major breakthroughs for
our lineage. For our australopithecine ancestors, the use
of tools meant they could incorporate more animal resources, like meat and bone marrow,
into their diets, consuming more calories than they’d been able to get before. And more calories meant more available energy,
allowing those early hominins to develop and maintain larger brains and bodies over time,
leading to taxa like Homo erectus. And the very circuitry of our brains might
also have started to change when we began making and using tools. In 2008, researchers at a medical school in
Indiana used PET scans to study the brains of modern expert stone toolmakers while they
made Oldowan and Acheulean tools. And the scans showed that toolmaking activated
parts of the brain associated with visual-motor coordination and planning. Demands in those parts of the brain also grew
as the toolmaking became more complex. So the researchers concluded that these neural
signatures of tool-making may suggest that our brains and our technological capabilities
may have co-evolved. And of course, the act of toolmaking may also
have had an effect on what we use to make them: our hands. In 2018, a team of anthropologists conducted
an experiment to learn more about how the biomechanical stresses of tool making might
have shaped our anatomy. Their study subjects wore special gloves with
sensors in them and then did things like nut-cracking, breaking bones for marrow, and making stone
tools, to see how much stress these things placed on each of their fingers. And the research showed that the two activities
that created the most stress were breaking bones for marrow and making stone flakes using
hammerstones. So, these two activities might have been especially
important in driving the evolution of our hands. Because, using tools in these ways would have
exerted powerful selective pressure on things like increased stability and better gripping
ability, and maybe even having bigger, stronger thumbs. From the size of our bodies to the wiring
of our brains and the capabilities of our hands, we owe some incredibly important aspects
of our modern anatomy to stone tools. But of course, they were only the beginning
of our capacity for technology. Their legacy continues to this day, and the
reason you can watch me talk to you right now is because our always-evolving ability
to create new things to help us interact with the world around us. Thank you to CuriosityStream for supporting
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