[DNA evidence shows that H. sapiens mated with groups including
Neanderthals and Denisovans. It even reveals evidence of other
“ghost populations” — groups who are part of our genetic code,
but whose fossils we haven’t found yet.]
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A NEW PICTURE OF WHEN WE MATED WITH OTHER KINDS OF HUMANS  
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Maddie Burakoff and Laura Ungar
September 24, 2023
AP
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_ DNA evidence shows that H. sapiens mated with groups including
Neanderthals and Denisovans. It even reveals evidence of other
“ghost populations” — groups who are part of our genetic code,
but whose fossils we haven’t found yet. _

Neanderthal Mother (detail of diorama), by Kojotisko (CC0 1.0)

 

What does it mean to be human?

For a long time, the answer seemed clear. Our species, Homo sapiens
— with our complex thoughts and deep emotions — were the only true
humans to ever walk the Earth. Earlier forms, like the Neanderthals,
were thought to be just steps along the path of evolution, who died
out because we were better versions.

That picture is now changing.

In recent years, researchers have gained the power to pull DNA from
ancient hominins
[[link removed]],
including our early ancestors and other relatives who walked on two
legs. Ancient DNA technology has revolutionized the way we study human
history and has quickly taken off, with a constant stream of studies
exploring the genes of long-ago people.

Along with more fossils and artifacts, the DNA findings are pointing
us to a challenging idea: We’re not so special. For most of human
history we shared the planet with other kinds of early humans, and
those now-extinct groups were a lot like us.

“We can see them as being fully human. But, interestingly, a
different kind of human,” said Chris Stringer, a human evolution
expert at London’s Natural History Museum. “A different way to be
human.”

What’s more, humans had close — even intimate — interactions
with some of these other groups, including Neanderthals, Denisovans
and “ghost populations” we only know from DNA.

A WORLD WITH MANY HOMININS

Scientists now know that after H. sapiens first showed up in Africa
around 300,000 years ago, they overlapped with a whole cast of other
hominins, explained Rick Potts, director of the Smithsonian’s Human
Origins Program.

[Ancient humans chart]

For much of history, Homo sapiens lived alongside other kinds of
ancient humans and even mated with some of them. (AP Graphic)

Neanderthals were hanging out in Europe. Homo heidelbergensis
[[link removed]] and Homo
naledi
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living in Africa. The short-statured Homo floresiensis
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sometimes known as the “Hobbit,” was living in Indonesia, while
the long-legged Homo erectus
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loping around Asia.

Scientists started to realize all these hominins weren’t our direct
ancestors. Instead, they were more like our cousins: lineages that
split off from a common source and headed in different directions.

Archaeological finds have shown some of them had complex behaviors.
Neanderthals painted cave walls
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Homo heidelbergensis hunted large animals
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rhinos and hippos, and some scientists think even the small-brained
Homo naledi was burying its dead
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South African cave systems. A study last week found early humans
were building structures with wood
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H. sapiens evolved.

Researcher also wondered: If these other kinds of humans were not so
different, did our ancestors have sex with them?

For some, the mixing was hard to imagine. Many argued that as H.
sapiens ventured out of Africa, they replaced other groups without
mating. Archaeologist John Shea of New York’s Stony Brook University
said he used to think of Neanderthals and H. sapiens as rivals,
believing “if they bumped into each other, they’d probably kill
each other.”

DNA REVEALS ANCIENT SECRETS

But DNA has revealed there were other interactions, ones that changed
who we are today.

In 2010, the Swedish geneticist Svante Paabo and his team pieced a
tricky puzzle together. They were able to assemble fragments of
ancient DNA into a full Neanderthal genome
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was long thought to be impossible and won Paabo a Nobel Prize last
year
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This ability to read ancient DNA revolutionized the field, and it is
constantly improving.

For example, when scientists applied these techniques to a pinky bone
and some huge molars found in a Siberian cave, they found genes that
didn’t match anything seen before
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Bence Viola, an anthropologist at the University of Toronto who was
part of the research team that made the discovery. It was a new
species of hominin, now known as Denisovans, who were the first human
cousins identified only by their DNA.

Armed with these Neanderthal and Denisovan genomes, scientists could
compare them to people today and look for chunks of DNA that match.
When they did, they found clear signs of crossover
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THE NEW HUMAN STORY

The DNA evidence showed that H. sapiens mated with groups including
Neanderthals and Denisovans. It even revealed evidence of other
“ghost populations” — groups who are part of our genetic code,
but whose fossils we haven’t found yet.

It’s hard to pin down exactly when and where these interactions
happened. Our ancestors seem to have mixed with the Neanderthals soon
after leaving Africa and heading into Europe. They probably bumped
into the Denisovans in parts of East and Southeast Asia.

“They didn’t have a map, they didn’t know where they were
going,” the Smithsonian’s Potts said. “But looking over the next
hillside into the next valley, (they) ran into populations of people
that looked a bit different from themselves, but mated, exchanged
genes.”

So even though Neanderthals did look distinct from H. sapiens — from
their bigger noses to their shorter limbs — it wasn’t enough to
create a “wall” between the groups, Shea said.

“They probably thought, ‘Oh, these guys look a little bit
different,’” Shea said. “‘Their skin color’s a little
different. Their faces look a little different. But they’re cool
guys, let’s go try to talk to them.’”

COMPLEX NEANDERTHALS

The idea that modern humans, and particularly white humans, were the
pinnacle of evolution came from a time of “colonialism and
elitism,” said Janet Young, curator of physical anthropology at the
Canadian Museum of History.

One Neanderthal painting, created to reflect the vision of a eugenics
advocate, made its way through decades of textbooks and museum
displays.

The new findings have completely upended the idea that earlier, more
ape-like creatures started standing up straighter and getting more
complex until they reached their peak form in H. sapiens, Young said.
Along with the genetic evidence, other archaeological finds have shown
Neanderthals had complex behaviors around hunting, cooking, using
tools and even making art.

Still, even though we now know our ancient human cousins were like us
— and make up part of who we are now — the idea of ape-like cave
men has been hard to dislodge.

Artist John Gurche is trying. He specializes in creating lifelike
models of ancient humans for museums, including the Smithsonian and
the American Museum of Natural History, in hopes of helping public
perception catch up to the science.

Skulls and sculptures gazed out from the shelves of his studio earlier
this year as he worked on a Neanderthal head, punching pieces of hair
into the silicone skin.

Bringing the new view to the public hasn’t been easy, Gurche said:
“This caveman image is very persistent.”

For Gurche, getting the science right is crucial. He has worked on
dissections of humans and apes to understand their anatomy, but also
hopes to bring out emotion in his portrayals.

“These were once living, breathing individuals. And they felt grief
and joy and pain,” Gurche said. “They’re not in some fairyland;
they’re not some fantasy creatures. They were alive.”

MANY CONNECTIONS STILL TO BE FOUND

Scientists can’t get useful genetic information out of every fossil
they find, especially if it’s really old or in the wrong climate.
They haven’t been able to gather much ancient DNA from Africa, where
H. sapiens first evolved, because it has been degraded by heat and
moisture.

Still, many are hopeful that as DNA technology keeps advancing,
we’ll be able to push further into the past and get ancient genomes
from more parts of the world, adding more brushstrokes to our picture
of human history.

Because even though we were the only ones to survive, the other
extinct groups played a key role in our history, and our present. They
are part of a common humanity connecting every person, said Mary
Prendergast, a Rice University archeologist.

“If you look at the fossil record, the archeological record, the
genetic record,” she said, “you see that we share far more in
common than what divides us.”

___

_The Associated Press Health and Science Department receives support
from the Howard Hughes Medical Institute’s Science and Educational
Media Group. The AP is solely responsible for all content._

_MADDIE BURAKOFF [[link removed]] is a
science writer based in New York. twitter
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_LAURA UNGAR [[link removed]] covers medicine
and science._

* Science
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* human origins
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* Evolution
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* Neanderthals
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* Denisovans
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