The team had journeyed across vast distances, traversing Africa and the Middle East before ultimately arriving at the shadowy woods of the newly discovered land. These individuals were distant ancestors belonging to our contemporary human lineage and counted amongst the initial Homo sapiens to set foot in Europe.
Over there, these individuals probably ran into their distant relatives:
Neanderthals
.
These smaller groups of ancient human cousins featured prominent brow ridges, sizable craniums, and stocky physiques, having adapted over vast periods to the harsher European environment. On multiple occasions throughout history, their kind intersected with early humans, intermingled, and even interbred.
Many millennia afterward, these primordial interactions continue to be evident within the genetic makeup of countless individuals living today. These persistent hereditary factors influence various aspects of our being, ranging from physical traits to susceptibility to illnesses.
In certain sections of our genetic makeup, we are more Neanderthal than truly human,
Joshua Akey
A professor of integrative genomics at Princeton University stated for Live Science.
These beings were our nearest human ancestors, and this is what they’ve left behind.
The first encounter
By 75,000 years ago
, but potentially as high as
250,000 years
A long time ago, the forebears of many contemporary Eurasian people initially set out from Africa and entered Eurasia. In this new land, modern humans encountered Neanderthals, who had their last shared ancestor with modern humans earlier in history.
hundreds of millennia prior
And have been residing in these continents ever since. Numerous times throughout the ages, these groups intermingled.
Related:
Could Neanderthals talk?
Initially, early modern humans obtained complete chromosomes from Neanderthals.
Sriram Sankararaman
A professor specializing in computer science, human genetics, and computational medicine at UCLA informed Live Science. Nonetheless, this occurs across generations through a mechanism referred to as
genetic recombination
These segments of DNA were fragmented and rearranged.
Neanderthal DNA was typically “detrimental” to modern humans, indicating it was quickly eliminated from the genetic makeup of contemporary humans through
evolution
This led to what researchers call “Neanderthal deserts” — extensive areas within the modern human genome where this genetic material is absent. For example, experts believe that the Y chromosome in men does not contain significant traces of Neanderthal DNA.
does not include any Neanderthal genetic material
It could be that the genes present on the Neanderthal Y chromosome were not compatible with other human genes, or they might have been inadvertently eliminated through a process called random loss.
genetic drift
.
In people who inherited Neanderthal DNA, the X-chromosome also contains
significantly lower Neanderthal heritage
This is presumably due to the fact that other, non-sex chromosomes have an additional protective mechanism since both copies must carry harmful or dysfunctional mutations for them to manifest. In contrast, male individuals do not possess a second, intact version of the X chromosome’s genes to counterbalance potentially detrimental mutations present there. Consequently, this situation would exert significant evolutionary force toward eliminating deleterious Neanderthal genetic material from the contemporary human X chromosome.
Emilia Huerta-Sanchez
, an associate professor of ecology, evolution, and organismal biology at Brown University, stated to Live Science.
However, certain segments of Neanderthal DNA aided the survival and reproduction of modern humans, which is why these remnants persist within our genetic makeup today. Currently, Neanderthal DNA comprises, on average,
2% of the genomes
Of individuals outside Africa, though the prevalence of Neanderthal DNA associated with advantageous characteristics can reach up to 80% in certain sections of the genome, according to Akey.
Our physical appearance
For numerous individuals, the heritage of Neanderthals is evident in a prominent characteristic: skin pigmentation.
A Neanderthal gene variant
on chromosome 9 that
influences skin color
is present in 70% of Europeans nowadays. An additional Neanderthal genetic variation, which can be found in the majority of East Asians,
regulates keratinocytes
, which
protect the skin
Defending against ultraviolet radiation through a dark pigment known as melanin.
Neanderthal genetic variations are likewise linked to
greater risk of sunburn
in modern humans. Likewise,
around 66% of Europeans
carry a Neanderthal gene associated with a
increased chance of children getting sunburned and having difficulty tanning well
.
In certain sections of our genetic makeup, we share more similarities with Neanderthals than with modern humans.
Joshua Akey from Princeton University
For thousands of years, Neanderthals lived in areas with higher latitudes where sunlight was less intense, which is necessary for
vitamin D production
As such, alterations in hair and skin physiology might have enabled contemporary humans to effectively utilize reduced amounts of sunlight while continuing to synthesize sufficient quantities of vitamin D for optimal health.
John Capra
, an evolutionary geneticist from Vanderbilt University, stated to Live Science.
“One of the exciting aspects of interbreeding is that rather than awaiting the emergence of new advantageous mutations, which can be quite a sluggish process, it introduces an immense amount of genetic diversity all at once,” effectively accelerating evolution, as stated by Huerta-Sanchez.
Related:
How do Neanderthals differ from Homo sapiens?
Moreover, our forebears needed to adjust to the frigid climate of Eurasia. They might have inherited Neanderthal genes that influenced facial structure. As reported in 2023,
study
, researchers found that contemporary humans acquired
tall-nose genes
From Neanderthals. A higher nose might have enabled more frigid air to be warmed up to body temperature within the nasal cavity prior to reaching the lungs, as proposed.
Kaustubh Adhikari
, who served as a co-senior study author and is a statistical geneticist at University College London.
The clock that drives our cellular rhythm
Neanderthal genetic material might have also been beneficial.
H. sapiens
adapt to the more significant variations in daylight duration between daytime and nighttime at higher latitudes.
Residual Neanderthal genes influence our circadian rhythm, which controls bodily functions like
body temperature
and
metabolism
For example, certain early risers might owe their gratitude to
Neanderthals with regard to their circadian clock genes
, as reported by Capra and colleagues.
This could have assisted our ancestors in adapting to shorter winter days further from the equator, according to Capra.
“Being a morning person doesn’t seem to be the crucial factor here,” Capra explained. “Instead, it’s an indication of how adaptable your internal clock is and how well it can adjust to changes in light-dark patterns throughout different times of the year,” he added.
Our internal defenses
A significant number of the Neanderthal genes that we still retain strongly are associated with immune response.
When Homo sapiens reached Europe, Neanderthals had already been battling Eurasian-specific infections for hundreds of thousands of years. Through interbreeding with Neanderthals, contemporary humans acquired these immediate benefits of enhanced genetic resistance to local diseases.
The segments of Neanderthal DNA, particularly those related to immunity—which had evolved over time to combat pathogens that Neanderthals had encountered for extended periods—began increasing in prevalence due to natural selection within contemporary human groups.
David Enard
, an associate professor from the department of Ecology and Evolutionary Biology at the University of Arizona, stated to Live Science.
Although numerous ancestral pathogens that afflicted early humans have been erased from history, certain Neanderthal genes that aided in combating these pathogens remain effective against contemporary microbes. For instance, a 2018 research conducted by Enard along with another researcher demonstrated this phenomenon.
Modern humans acquired Neanderthal DNA through inheritance.
that helped them combat
RNA
viruses, which now encompass
the flu (influenza)
,
HIV
and
hepatitis C
.
Related:
10 Surprising Ways Neanderthal Genes Influence Our Well-being
The shadowy aspect of Neanderthal genetics
Certain Neanderthal genes that previously aided our forebears could now be detrimental in today’s society.
Primarily, Neanderthal genes show minimal expression in the brain, suggesting they faced strong negative selection throughout evolution. These genes have also been associated with mood disorders.
such as depression
as well as neural signaling pathways that increase the likelihood of individuals becoming
addicted to nicotine
.
And even the immunity enhancement from Neanderthals might come with a drawback. For instance, in 2016,
scientists
discovered
those Neanderthal genes that enhance the immune system’s ability to combat pathogens might also
make individuals susceptible to allergies
Moreover, Neanderthal DNA has been linked to an increased likelihood of contracting autoimmune disorders, including
Graves’ disease, caused by an overactive thyroid; and rheumatoid arthritis
, which causes inflammation in the joints and even ”
Viking disease
where one or more fingers get stuck or locked in position.
A single Neanderthal genetic variation might have increased our likelihood of experiencing a severe case of illness.
COVID-19
That particular variant, located on chromosome 3, is
identified among half of South Asians
And one-sixth of Europeans. However, even this scenario is complex because additional Neanderthal genes found in up to half of individuals across Eurasia and the Americas have different associations.
lowered chance of serious COVID-19.
“Sadly, there aren’t any illnesses or traits we can definitively attribute to Neanderthal DNA,” Capra explained.
This is particularly applicable to many major health issues, like
heart disease
and
cancer
, where numerous genes, along with various environmental factors, influence your likelihood of developing diseases.
What lies ahead
How long will the remnants of these ancient humans persist within our genetic code? Over hundreds of thousands of years, certain Neanderthal segments will slowly vanish from our DNA. In contrast, others will integrate more deeply into our genome, as Akey mentioned.
For now, there remains significantly more to uncover regarding how Neanderthals imprinted themselves upon our legacy.
“Leveraging advanced genomic technologies such as
CRISPR
And gene editing will be crucial for comprehending the fundamental biology behind how Neanderthal sequences influence human characteristics and disorders,” Akey stated.
Understanding the actual functions of these genes might help in the creation of therapies for specific ailments, he mentioned.
And gene flow was not unidirectional; researchers are also working to ascertain the influence of modern human DNA.
may have influenced Neanderthals
and are utilizing AI techniques on ancient genomes to generate
a more detailed picture
about what our distant relatives might have been like.
Determining the function of Neanderthal DNA within our genetic makeup serves not only to enhance our understanding of our well-being but also offers insights into what sets us apart from one another, according to Sankararaman.
Sankararaman stated that Neanderthal DNA integrated with our genomes during a crucial period in our past, specifically when our forebears were venturing into unfamiliar habitats.
“By examining the destiny of these segments of DNA,” he stated, “we may gain insight into which areas were functionally significant within our genome during this timeframe.”
