Hi, it’s Hank with news about some new benefits for our Patreon Patrons! People pledging $15 or more now have access
to a quarterly livestream with the Eons team! And if you pledge $100 a month, you can actually
take part in the actual video stream and nerd out with us face to face! Sound fun? You can go to patreon.com/eons to find out more But now, let’s talk about some planetary
domination. Today, our species - Homo sapiens - lives
on every continent on Earth. There are more than seven billion of us, inhabiting
almost every possible environment, and altering them through our use of culture and technology
to suit our needs. We can survive harsh winters, irrigate deserts,
and travel at will to reach the most remote islands. But we weren’t always so widespread. One of the defining features of our species
is that we’re behaviorally flexible. We can use whatever resources are around in
order to survive. We’ve been like this for a long time, and
it’s a big part of the story of our success. The early ancestors that we call the first
anatomically modern humans were more like us than any other member of the genus Homo,
with more slender skeletons; smaller, less protruding jaws and teeth; and really big
brains. These ancestors had to be able to adapt to
all kinds of new environments as they spread around the world. And adapt they did. They encountered other hominin species, faced
new predators and diseases, and found the food and shelter they needed to thrive in
new landscapes. And we can actually trace the path they took,
from our deepest origins in Africa all the way to the Americas, by looking at the fossils
and archaeological materials they left behind, as well as in the genomes of their descendants:
our genomes. Now, we don’t know all the details of this
journey, but we can say for sure that it was an epic one. In the last 300,000 years or so, we’ve gone
from inhabiting a single continent to all of them. Our story as a species is one of constant
migration. So, no discussion of human evolution would
be complete without a deep look through that short window of time when we took over the
world. Based on our current understanding of the
evidence, the story of Homo sapiens begins in Africa, between 300,000 and 350,000 years
ago. In 1961, miners working at a site called Jebel
Irhoud in Morocco accidentally unearthed the fossil remains of a hominin with facial features
that were surprisingly like those of modern humans. But at the time, the remains couldn’t be
dated precisely. And in the last few years, anthropologists
have gone back to that site and found even more fossils - including another skull. This new one had the same mix of modern facial
features, like smaller brow ridges, and also more basal traits, like a braincase that was
longer and lower than the ones we have today. And researchers were able to date these new
finds to between 300,000 and 350,000 years ago - a surprisingly early date for hominins
with such modern-looking faces. Before that find was made, the oldest known
remains of modern humans were skulls from two sites in Ethiopia, dated to 195,000 and
160,000 years ago, respectively -- more than 100,000 years younger than the material from
Jebel Irhoud. And while these younger skulls share some
features with us -- like the same shape and size of their braincase -- they’ve still
got some fairly robust features, too -- like heavy brow ridges -- which we associate with
more archaic hominins. So we’ve got fossil evidence of early Homo
sapiens from northern and eastern Africa. But the evidence in our genes paints a slightly
more complicated picture. Our genomes can be used to infer the history
of our migrations, by comparing the DNA from human populations in different places, and
seeing how they differ. Variations in our genomes are generally thought
to correspond to how far apart certain populations have been separated, in both distance and
time. Groups that live closer to each other are
expected to be more similar, while groups living farther apart are expected to be more
different. And older, more ancestral lineages typically
have more genetic diversity than newer ones. So based on the DNA we’ve studied of living
peoples, there’s evidence for modern human origins all over Africa, not just the north
and the east. African populations turn out to have the greatest
genetic diversity of any group of people in the world. So this suggests that their lineages are older. Meanwhile, all of the populations outside
of Africa have just a fraction of the diversity found in Africa, suggesting that their variations
are more recent. But the pattern of genetic variation found
within populations in sub-Saharan Africa points to a complicated history of migration, genetic
exchange, and selection. And in the end, that makes it impossible to
pinpoint a single place in Africa as the origin of modern humans. In any case, we do know that, after arising
in Africa, some groups of Homo sapiens started to spread to other continents. Anthropologists usually draw these migrations
as one-way arrows on a map, but that oversimplifies what was likely a more complex process. Some populations expanded but then contracted
again, and some moved back and forth between populations in various places. So we’re not sure who the first modern humans were to leave Africa, or even how many times they made the journey. We also have questions about what route these
migrants took: Some fossil evidence suggests that they went north, through that region
of the eastern Mediterranean known as the Levant, about 100,000 years ago. But there’s genomic evidence of a possible
southern route, which might have gone from Ethiopia into the southern part of the Arabian
peninsula and from there into Asia and Oceania. If we follow the northern route first, we
find fossil evidence at two sites in what’s now Israel. One of them is called Misliya Cave. In 2018, anthropologists published their discovery
of half of an upper jaw with teeth that are unmistakably human, along with evidence of
hearths and well-developed stone tool technology. Dated between 177,000 and 194,000 years ago,
this site is considered by many to be the earliest known evidence of modern humans outside
of Africa. Another site, called Skhūl, is part of the
same complex as Misliya Cave, but it’s more recent, dated to 100,000 to 135,000 years
ago. Excavated in the early 1930s, it has yielded
the remains of at least 10 adults, some of which appeared to have been intentionally
buried, providing early evidence of modern human behavior. Even further across the globe, there are two
sites in southern China with modern humans that overlap in time with those at Skhul. And we don’t know how these populations
got there -- like, whether they came from the Levant or by that southern route into
the Arabian peninsula. One site is known as Luna Cave in the region
known as Guangxi. It has produced just two teeth, only one of
which could be definitely assigned to Homo sapiens, and both were dated to between 70,000
and 127,000 thousand years ago. The other site is Fuyan Cave in Hunan Province,
and it has yielded 47 teeth, all from modern humans, and they’ve been dated to between
80,000 to 120,000 years ago. Teeth: They last! But what happened when our ancestors made
it to the edges of mainland Asia? Well, the only way to go from there seemed
to be across open water, which would’ve presented its own challenges. Sea levels did vary in the Pleistocene Epoch,
and probably made some crossings a little easier, but our ancestors still would’ve
had to find a way to get to the islands of Southeast Asia. And we don’t know how they did it, but we
know they got there. On the island of Sumatra in Indonesia there’s
a cave site called Lida Ajer, where modern human teeth have been found. They’ve been dated to between 63,000 and
73,000 years ago, and they represent the earliest known occupation of a rainforest by modern
humans, again demonstrating our ability to adapt. And from these islands, our ancestors continued
on through Oceania to Australia. Archaeological evidence suggests that anatomically
modern humans reached northern Australia between 50,000 and 60,000 years ago, leaving behind
stone tools and animal remains at a site called Madjedbebe. And for a while, that was the southernmost
extent of our species’ reach. But what was happening to the north? What happened to the populations that dispersed
into the Levant and then turned northwest instead of southeast? Well, the first modern humans that showed up in Europe
at two different sites at around the same time, about 43,000 years ago. We’ve found their teeth, of course, at a site in southern
Italy called Grotta del Cavallo and a jaw fragment from a site known as Kent’s Cavern
in the UK. But these sites are more than 2000 kilometers
apart. So, when it comes to how and when the rest
of Central Europe was settled, we’re missing a lot of evidence. The rest of the human journey starts in Siberia,
with some seriously adventurous populations that crossed the Bering land bridge into North
America. Again, based on genomic data, it seems likely
the native peoples of the Americas made their move between continents around 16,000 years
ago. Humans become much more widespread in North
America between 12,600 and 13,000 years ago, with the rise of the Clovis complex, a
type of stone tool technology that’s found across North America but isn’t necessarily
associated with any one group of people. Remains that have been found with these distinctive
tools have shown that members of this complex were the ancestors of many Native American
peoples today. And the same kind of expansion was occurring
in South America around the same time. The earliest site on that continent is the
Monte Verde site in Chile, dated to 14,500 years ago. It preserves the remains of hearths, and tools
and artifacts made of reed, bone, and stone. No teeth though The fact that people appeared at the southern
tip of the Americas so long ago suggests that humans might have quickly migrated south along
the Pacific coast, almost as soon as the peopling of the continents was possible. And that’s the whirlwind tour of our global
journey as a species. Homo sapiens arises as a species in Africa,
maybe as early as 300,000 years ago. The earliest fossils of modern humans outside
of Africa come from caves in Israel, dated to between 177,000 and 194,000 years ago. Some members of our species make it across
much of mainland Asia to southern China around 100,000 years ago, give or take 20,000 years. From there, they venture to Australia between
50,000 and 60,000 years ago. And they’re also found at two sites in Europe
around 43,000 years ago. The last continents to be reached were North
and South America, starting around 16,000 years ago. We’ve covered a tremendous amount of ground
in a short time, geologically speaking. But our origin is on the African continent,
and it remains central to our story as a species and as a genus. Our greatest genomic diversity as a species,
to this day, is there. And as genomic techniques improve and as more
exploration and excavation becomes possible, we’re learning more and more about how and
when we expanded across the world. Plus, we know we weren’t alone on this global
journey. We encountered and interbred with archaic
hominin populations within and outside of Africa along the way. But that’s a story for another time. Today's episode was recorded in the Konstantin Haase studio. Thanks to Konstantin and this month’s Eontologists: Jake Hart, Jon Ivy, John Davison Ng, and Steve. for their support on Patreon Thanks for joining us here on Eons if you want a whole new show to fall in
love with, then you MUST check out Monstrum, a new show from PBS Digital Studios that explores
monsters and myths from cultures around the world. Don’t be afraid! It’s only monsters!
This series constantly blows my mind. They have a video called, “the time it rained for two million years.” Two million years!