The Times Australia
The Times World News

.

DNA from elusive human relatives the Denisovans has left a curious mark on modern people in New Guinea

  • Written by Irene Gallego Romero, Senior Lecturer in Human Genetics, The University of Melbourne
DNA from elusive human relatives the Denisovans has left a curious mark on modern people in New Guinea

An encounter with a mysterious and extinct human relative – the Denisovans – has left a mark on the immune traits of modern Papuans, in particular those living on New Guinea Island.

This is a new discovery we describe in a study published in PLoS Genetics[1] today. It further suggests that our modern human diversity didn’t just evolve – some parts of it we got from other, extinct human groups.

DNA from our evolutionary cousins

Humans are the only living species of the Homo genus. But until 50,000 years ago, our ancestors coexisted – and sometimes interacted – with multiple other Homo groups across the globe. Most of them we know only by sparse archaeological remains[2], which offer tantalising glimpses of our evolutionary cousins.

But for two groups there is something else: DNA. Thanks to technological advances, scientists have retrieved DNA from fossils and sequenced it. As a result, we now have complete genome sequences of the best-known archaic hominins, the Neanderthals[3], and a far more elusive group, Denisovans[4].

Read more: Fresh clues to the life and times of the Denisovans, a little-known ancient group of humans[5]

Although many Neanderthal fossils have been unearthed all over Europe since they were first identified in the 1860s, the number of known Denisovan fossils fits in the palm of a hand – literally!

The genome sequence we have comes from the smallest bone of a pinky finger. It belonged to the 60,000-year-old remains of a teenage girl from a cave in Siberia, the largest known Denisovan fossil until recently.

The outline of a skeleton finger on a dark surface with a small, orange bone sitting atop one knuckle
A museum replica of the Denisovan finger bone used to extract ancient DNA. Thilo Parg/Wikimedia Commons, CC BY-SA[6][7]

Traces of ancestors

These genome sequences have transformed the way we think about our extinct relatives. For one, they quickly demonstrated that as humans expanded outside Africa, we had sex – and children – with these other populations.

Traces of their genomes linger in individuals alive today, transmitted across hundreds of generations.

Read more: Evolutionary study suggests prehistoric human fossils 'hiding in plain sight' in Southeast Asia[8]

In the case of Neanderthals, these traces are in all individuals of non-African ancestry today. In the case of Denisovans, we find small traces of their genome in people from all over Asia – especially in Papua New Guinea, and in the island nations of Southeast Asia, where individuals may owe up to 4–5% of their genome to these ancestors.

But identifying these fragments of DNA in our genomes is only the beginning.

The DNA makes a difference

The real challenge is to find the biological consequences of this DNA for the people who carry it – which, it bears remembering, is the vast majority of humans. Our specific research question was to pinpoint the molecular processes that might be affected by its presence.

Studies of Neanderthal DNA have shown that genetic variants inherited from them can alter the levels[9] at which some human genes are expressed, for example. We also know Neanderthals have contributed to our immune systems[10] (including differences in how people respond to infection with COVID-19), and to variation in skin and hair colour[11].

Read more: What teeth can tell about the lives and environments of ancient humans and Neanderthals[12]

But it has never been clear whether Denisovan DNA has left similar trends in modern humans.

In 2019, a study revealed[13] the genomic coordinates where Denisovan DNA might be found within the genome of Papuan individuals – that is, the indigenous people of New Guinea Island – alive today.

This led us to begin looking into these regions, to understand the cellular and biological processes that might be affected by Denisovan DNA. We took a hybrid approach to this question, making computational predictions first, and following up with laboratory-based experiments to validate our findings.

In addition, we took advantage of the known Neanderthal DNA within these people to highlight any Denisovan-specific contribution. This gave us a more integrated understanding of how encounters with these relatives left potential biological and evolutionary consequences in modern humans.

A unique Denisovan contribution

We noticed that in Papuans, Denisovan and Neanderthal genetic variants both occasionally occur within parts of the genome responsible for modulating the expression levels of nearby genes.

However, only Denisovan variants are consistently predicted to occur and affect elements controlling the expression levels of immune-related genes.

So, these different sources of DNA might contribute to the genetic and phenotypic diversity within Papuans in different ways.

To validate our predictions, we designed an experiment comparing five Denisovan sequences against their modern human counterpart, and tested their ability to actually affect gene expression levels inside a particular kind of immune cell known as a lymphocyte.

In two of the five cases, the Denisovan variants did have a measurably different impact on the gene expression levels than their modern human counterpart. And they impact genes known to be important players in the response to infectious microbes, including viruses.

The fact that Denisovans, but not Neanderthals, seem to have contributed to the immune systems of present-day Papuans, tells us something about these ancient people, too.

Although little is known about how widely through Asia Denisovans lived, it suggests their immune system changed to adapt to the infectious diseases of their environment.

When humans moved in 60,000 years ago[14], these bits of DNA likely contributed to our success in settling this part of the world.

While our study is the first to elucidate the contribution of Denisovan DNA within modern human genetic diversity, there are still exciting questions to address. In particular, it is not clear whether the overall contributions of Denisovan and Neanderthal genetic variants consistently differ from each other.

It is also important to note we tested genetic variants in immune cells under resting conditions. This means the same or other genetic variants might have different effects out in the environment – this will be an important question for studies in the future.

Read more: First-ever genetic analysis of a Neanderthal family paints a fascinating picture of a close-knit community[15]

References

  1. ^ in a study published in PLoS Genetics (doi.org)
  2. ^ sparse archaeological remains (onlinelibrary.wiley.com)
  3. ^ Neanderthals (www.sciencemag.org)
  4. ^ Denisovans (www.nature.com)
  5. ^ Fresh clues to the life and times of the Denisovans, a little-known ancient group of humans (theconversation.com)
  6. ^ Thilo Parg/Wikimedia Commons (commons.wikimedia.org)
  7. ^ CC BY-SA (creativecommons.org)
  8. ^ Evolutionary study suggests prehistoric human fossils 'hiding in plain sight' in Southeast Asia (theconversation.com)
  9. ^ can alter the levels (doi.org)
  10. ^ our immune systems (linkinghub.elsevier.com)
  11. ^ variation in skin and hair colour (www.nature.com)
  12. ^ What teeth can tell about the lives and environments of ancient humans and Neanderthals (theconversation.com)
  13. ^ a study revealed (www.cell.com)
  14. ^ 60,000 years ago (science.sciencemag.org)
  15. ^ First-ever genetic analysis of a Neanderthal family paints a fascinating picture of a close-knit community (theconversation.com)

Read more https://theconversation.com/dna-from-elusive-human-relatives-the-denisovans-has-left-a-curious-mark-on-modern-people-in-new-guinea-196113

Times Magazine

Building a Strong Online Presence with Katoomba Web Design

Katoomba web design is more than just creating a website that looks good—it’s about building an online presence that reflects your brand, engages your audience, and drives results. For local businesses in the Blue Mountains, a well-designed website a...

September Sunset Polo

International Polo Tour To Bridge Historic Sport, Life-Changing Philanthropy, and Breath-Taking Beauty On Saturday, September 6th, history will be made as the International Polo Tour (IPT), a sports leader headquartered here in South Florida...

5 Ways Microsoft Fabric Simplifies Your Data Analytics Workflow

In today's data-driven world, businesses are constantly seeking ways to streamline their data analytics processes. The sheer volume and complexity of data can be overwhelming, often leading to bottlenecks and inefficiencies. Enter the innovative da...

7 Questions to Ask Before You Sign IT Support Companies in Sydney

Choosing an IT partner can feel like buying an insurance policy you hope you never need. The right choice keeps your team productive, your data safe, and your budget predictable. The wrong choice shows up as slow tickets, surprise bills, and risky sh...

Choosing the Right Legal Aid Lawyer in Sutherland Shire: Key Considerations

Legal aid services play an essential role in ensuring access to justice for all. For people in the Sutherland Shire who may not have the financial means to pay for private legal assistance, legal aid ensures that everyone has access to representa...

Watercolor vs. Oil vs. Digital: Which Medium Fits Your Pet's Personality?

When it comes to immortalizing your pet’s unique personality in art, choosing the right medium is essential. Each artistic medium, whether watercolor, oil, or digital, has distinct qualities that can bring out the spirit of your furry friend in dif...

The Times Features

How much money do you need to be happy? Here’s what the research says

Over the next decade, Elon Musk could become the world’s first trillionaire[1]. The Tesla board recently proposed a US$1 trillion (A$1.5 trillion) compensation plan, if Musk ca...

NSW has a new fashion sector strategy – but a sustainable industry needs a federally legislated response

The New South Wales government recently announced the launch of the NSW Fashion Sector Strategy, 2025–28[1]. The strategy, developed in partnership with the Australian Fashion ...

From Garden to Gift: Why Roses Make the Perfect Present

Think back to the last time you gave or received flowers. Chances are, roses were part of the bunch, or maybe they were the whole bunch.   Roses tend to leave an impression. Even ...

Do I have insomnia? 5 reasons why you might not

Even a single night of sleep trouble can feel distressing and lonely. You toss and turn, stare at the ceiling, and wonder how you’ll cope tomorrow. No wonder many people star...

Wedding Photography Trends You Need to Know (Before You Regret Your Album)

Your wedding album should be a timeless keepsake, not something you cringe at years later. Trends may come and go, but choosing the right wedding photography approach ensures your ...

Can you say no to your doctor using an AI scribe?

Doctors’ offices were once private. But increasingly, artificial intelligence (AI) scribes (also known as digital scribes) are listening in. These tools can record and trans...