Our inner Neanderthals are still here.
Our early Homo sapiens ancestors coexisted with these distant cousins of
ours, as well as other species known as Denisovans. As they socialized, they
had kids. It's in our DNA, so part of who they were never really
disappeared. And the extent to which that shapes us is beginning to be shown
by science.
Scientists are discovering that characteristics passed down from our
ancient cousins still exist in us today. These features impact our immune
systems, fertility, and even how our bodies responded to the COVID-19 virus.
This is made possible by the new and quickly developing capacity to put
together bits of ancient DNA.
"We're now carrying the genetic legacies and learning about what that means
for our bodies and our health," told the Rice University archaeologist Mary
Prendergast.
Researchers have discovered connections between Neanderthal DNA and a
severe hand ailment, nasal morphology, and other human characteristics just
in the last few months. In order to study the gene's biological
consequences, scientists even introduced a gene carried by Neanderthals and
Denisovans into mice, discovering that it gave the animals bigger heads and
an additional rib.
There is still much to learn about the human experience. However, according
to Dr. Hugo Zeberg of the Karolinska Institute in Sweden, fresh research,
partnerships, and technological advancements are assisting scientists in
starting to address the fundamental but cosmic questions: "Who are we? From
where did we originate?"
Furthermore, the responses reveal a startling truth: Despite our best
efforts, we share a great deal more traits with our extinct relatives.
NAEDERNTHALS INSIDE THE US
Up until recently, scientists could only deduce information about the size
and shape of bones, which meant that the genetic heritage of prehistoric
humans remained hidden. However, there has been a constant flow of new
findings derived from ancient DNA, a field of research made possible by
Nobel laureate Svante Paabo, who was the first to piece together a
Neanderthal genome.
Scientists have been able to see things like genetic changes through time
to better adapt to settings or via chance because to advancements in the
discovery and interpretation of ancient DNA.
Even the amount of genetic material that individuals from various places
share with our ancestors' old cousins may be determined.
Neanderthal DNA is found in 1% to 2% of groups from European and Asian
ancestries, but virtually nonexistent in some African populations, according
to research. In most areas of the world, Denisovan DNA is hardly noticeable;
nevertheless, it accounts for 4% to 6% of the DNA of individuals living in
Melanesia, which stretches from New Guinea to the Fiji Islands.
Even if it doesn't seem like much, it adds up. Zeberg, who works closely
with Paabo, stated that "Half of the Neanderthal genome is still around, in
small pieces scattered around modern humans."
It's also sufficient to have a very real impact on us. Although the entire
extent is yet unknown, scientists are discovering that it can have both
positive and negative effects.
Neanderthal DNA, for instance, has been connected to autoimmune conditions
including rheumatoid arthritis and Graves' disease. Homo sapiens did not
have immunity to illnesses found in Europe and Asia when they left Africa,
but Neanderthals and Denisovans who were already residing there had.
"We got a quick fix to our immune systems by interbreeding with them, which
was good news 50,000 years ago," said Chris Stringer, a specialist on human
evolution at the Natural History Museum in London. As a result, some people
now claim that their immune systems are hypersensitive and occasionally go
into self-destruct mode.
A gene linked to blood clotting that is thought to have originated from
Neanderthals in Eurasia would have also been useful in the "rough and tumble
world of the Pleistocene," according to Rick Potts, the director of the
Smithsonian Institution's human origins department. But as of right now, it
can increase an older adult's risk of stroke. He declared, "There are costs
in evolution for every benefit."
Zeberg and Paabo's 2020 study discovered that a significant genetic risk
factor for severe COVID-19 is inherited from Neanderthals. "It was a perfect
match when we compared it to the Neanderthal genome," Zeberg stated. "I
almost toppled over in my chair."
The next year, researchers discovered that a group of DNA variations on a
single chromosome that descended from Neanderthals had the reverse effect,
shielding humans against severe COVID.
The list continues: Neanderthal genetic variations have been connected in
studies to behavioral characteristics, skin and hair color, cranial form,
and Type 2 diabetes. According to one study, those who report experiencing
greater pain than others probably have Neanderthal pain receptors in their
bodies. An other study discovered that one-third of European women have a
Neanderthal progesterone receptor, linked to higher fertility and fewer
miscarriages.
Much less is known about the Denisovan genetic heritage we carry with us,
despite some studies connecting their genes to improved fat metabolism and
altitude adaption. The University of Chicago's Maanasa Raghavan, a
specialist in human genetics, reported that Tibetans, who still survive in
low-oxygen conditions, had a portion of their Denisovan DNA.
Even within the genetic code of contemporary humans, scientists have
uncovered evidence of "ghost populations"—groups whose remains have not yet
been unearthed.
WHY, THEN, DID WE ENDURE?
The story of modern humans' survival, according to Potts, "was always told
as some success story, almost like a hero's story," in which humans
triumphed against the "insufficiencies" of their cousins and ascended above
the rest of nature.
"Well, that's just not the right story at all."
When Homo sapiens departed Africa, Neanderthals and Denisovans had already
been there for thousands of years. It was formerly believed by scientists
that our greater technology and more complicated behavior was the reason we
prevailed. However, new findings indicate that Neanderthals were able to
communicate, used fire for cooking, created art, used complex tools, hunted,
and even wore jewelry and cosmetics.
Many ideas now link our capacity for long-distance travel to our ability to
survive.
Zeberg declared, "We spread all over the world, much more than these other
forms did."
Potts noted that whereas Neanderthals had evolved specifically for cold
environments, Homo sapiens, having originated in tropical Africa, were able
to spread to any type of climate. He declared, "We are so culturally and
geographically adaptive to so many places in the world."
Eleanor Scerri, an archaeologist at Germany's Max Planck Institute for
Geoanthropology, stated that Neanderthals and Denisovans likely found
themselves stuck in tiny places due to severe circumstances including
recurring ice ages and ice sheets. They were more vulnerable to genetic
collapse since they were in smaller numbers.
We also possessed agile, productive bodies, according to Prendergast.
Neanderthals had greater difficulty surviving and moving around than modern
humans since it takes a lot more energy to support the stocky animals than
it does for the relatively slender humans. This was especially true when
food became limited.
The Canadian Museum of History's Janet Young, the curator of physical
anthropology, brought attention to another fascinating theory that
anthropologist Pat Shipman mentioned in one of her books: that dogs were
crucial to human survival. The skulls of domesticated dogs were discovered
by researchers in Homo sapiens sites at a considerably earlier epoch than
previously known. Scientists think that dogs simplified hunting.
All other species of hominins on Earth had vanished by 30,000 years ago,
leaving just Homo sapiens as the surviving species.
'MIXTURE AND INTERACTION'
Nevertheless, each new scientific finding emphasizes how much we still owe
our prehistoric relatives.
According to University of Wisconsin-Madison paleoanthropologist John
Hawks, "survival of the fittest and extinction" was not the guiding
principle of human evolution. It is concerned with "interaction and
mixture."
With scientific advancements enabling them to extract information from
ever-tinier remains of ancient life, researchers anticipate learning more.
Modern scientists are able to extract DNA from the soil and silt that
previously supported prehistoric humans, even in the absence of
remains.
Additionally, they aim to study more in less-traveled parts of the globe.
Zeberg stated that it is expected that additional nations would develop
"biobanks" that gather biological samples.
Scientists anticipate to uncover much more evidence of our genetic heritage
as they continue to explore how much of our ancient cousins influenced
us.
Zeberg remarked, "Maybe we shouldn't see them as so different."
