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.

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