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Scientists often use the phrase “anatomically modern humans” to describe the point when our ancient ancestors looked like us. But when did humans become behaviorally modern?

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Scientists often use the phrase “anatomically modern humans” to describe the point when our ancient ancestors looked like us: large skull, high forehead, small-ish jaw. And they think that happened roughly 200,000 years ago.

But the shape of their skulls doesn’t necessarily tell us how those people thought. So, when did our ancestors’ brains become capable of symbolic thinking, advanced problem solving, and writing song lyrics? In other words, when did Homo sapiens become behaviorally modern?

Well, it’s pretty hard to tell that from the fossil record. It’s not like singing — or other behaviors — can be fossilized! Plus, there was no eureka moment when we became behaviorally modern.

Skills like planning, creativity, and speech evolved slowly over millions of years. So, to figure this out, scientists look at migration patterns, stone tools, carved shells, cave art, and other artifacts. And they speculate whether those things required basic brain power or more advanced smarts.

And that’s been enough to give us a rough idea of what happened when. For example, one thing they study is hafted weapons — spears made by mounting a sharpened stone or bone onto a stick. Because while making basic stone tools requires some foresight and imagination, you don’t need what scientists consider modern levels of problem-solving.

The oldest hafted spears date from about 500,000 years ago, but they’re more common starting around 300,000 years ago. To make them, our ancestors sharpened stone or bone tips and whittled sticks into a shaft. Then, by about 70,000 years ago, they had developed an especially complex version of this process: They’d invented glue.

They mixed together things like sticky tree gum, crushed ochre rocks, and fat, and cooked them over a fire to attach the spearhead to the stick. They experimented with different ingredients, temperatures, and cooking times to manufacture the sturdiest weapons. Archeologists have recreated this process, and they found that the innovation, trial-and-error, and mental flexibility required was a challenge even for them.

And they can, like, ask a chemist for help. Speaking of which, the ancient hominins who made these tools would have had to ask each other for tips on how to make the strongest glue and the sharpest stones. They also needed to communicate effectively to migrate long distances to new territories.

Which gives us a clue to when language entered the picture. Based on migration patterns, anatomy, and tool-making, most scientists estimate that our ancestors could produce well-formed, meaningful sentences by around 200,000 years ago -- though some argue truly modern language is only 50,000 years old. So, by a couple hundred thousand years ago, our ancestors probably had fairly sophisticated language and planning skills.

But what about the most defining characteristics of behaviorally modern humans: abstract thought and creativity? Scientists see evidence of that in a special kind of rock: ochre. Ochre refers to any rock rich in iron oxide that yields red, yellow, or brown pigments.

Our ancestors made these pigments by scraping or crushing ochre with a stone tool, mixing the powder with water, and sometimes heating it to transform it from yellow to red. They then used these pigments — especially red — to paint tools, beads, shells, and possibly their bodies. Scientists think this indicates that the colorful decoration symbolized something to these communities.

The oldest evidence of our ancestors using these pigments are a couple of scraped ochre rocks from Kenya dating to about 300,000 years ago. But archaeologists have uncovered more advanced uses of ochre dating to around 100,000 years ago. At a site known as Blombos Cave in South Africa, they found ochre-processing toolkits made of shells, stones and bones.

They also unearthed an engraved piece of ochre that is considered the oldest piece of abstract art in the world. In a 2020 study, scientists used the Blombos Cave ochres to investigate how symbolic behavior may have evolved. Researchers took ochre and ostrich shells that our ancestors had engraved with lines and hashtag patterns between 110,000 and 52,000 years ago.

The scientists showed these ancient carvings to modern humans and asked them to remember and reproduce them. They found that, as the engravings became more recent, participants paid more attention to them, remembered them better, and drew them more accurately. The scientists concluded that, as the engravings evolved, they became more effective at provoking a cognitive response in the viewer.

We don't know whether the engravers intended to inspire aesthetic pleasure, or convey group identity, or something else. Whatever it was, the researchers don’t think the lines represented anything, like trees or people or cheeseburgers. In other words, this doesn’t provide evidence that these ancient hashtaggers were yet fully capable of symbolic, abstract thought.

But it does suggest they were at least on their way to a more modern way of thinking. The first examples of clearly symbolic, representational art that we know of are animal drawings from a cave in Borneo. One of these images dates to at least 40,000 years ago.

And the first evidence of musical instruments dates to around the same time: two 42,000-year-old flutes unearthed in Germany. So the consensus is that humans were only definitely behaviorally modern 40,000 to 50,000 years ago, when symbolic art and artifacts start to appear more consistently. But it’s really hard to know for sure.

Understanding how we became behaviorally modern can help us understand how, when, and why our ancestors migrated across the earth. It can tell us what cultures and skills they brought with them, and whether those abilities helped them outcompete other species of hominins. It can teach us how we developed the cognitive qualities that distinguish us from our ancestors and other creatures.

Ultimately, it reveals more about what it means to be human. And hey, I know of some especially great humans who are definitely capable of symbolic thought: it’s our patrons. We are pretty sure hundreds of thousands of years of behavioral evolution were leading up to you specifically.

Patrons make it possible for us to make videos like these every single week, and to put them up for free. If you would like to help us do that, check out [ ♪OUTRO ].