Let's start somewhere unexpected. In Estonia, there is a cult movie called "Tulnukas" ("The Alien") where local thugs use "Neanderthal" as a common insult, implying that the other person is stupid and primitive. This stereotype persists globally. You, however, have dedicated your career to rehabilitating their image, proving they were intelligent and sensitive. Do you feel like a "defense attorney" for Neanderthals and does it bother you when their name is still used as a slur?

I wouldn't say I have an agenda like that, actually. Yes, there's a certain stereotype of Neanderthals as primitive, brutish and insensitive. But there's also the opposite extreme where people idealize them. I don't know if you're familiar with Jean M. Auel, the author of "The Clan of the Cave Bear" and other books that were very popular about 20 years ago. In her stories, Neanderthals meet modern humans and are portrayed as incredibly kind, emotionally rich and possessing abilities modern humans supposedly lack.

Of course, the fact that we interbred with them — that we had children together and that those children were successful enough in human societies to pass on their genes — does tell us something. But we still don't really know what all these interactions looked like or how they happened.

Do we know what the relationship between Homo sapiens and Neanderthals was like? Was it aggressive? Was there violence? But we don't know these things, right?

How we imagine those interactions says more about our own fantasies, perhaps even sexual fantasies, than about what actually happened back then. It could have been the most beautiful love story of our species. Or it could have been rape. We simply don't know.

Your work has fundamentally shifted our perception of Neanderthals — they are no longer seen as brutish cavemen, but as our close relatives with whom we interbred. We carry their genes. Does the knowledge that we have a "piece of another species" inside us change how we define "humanity"? Where do you draw the biological line between "us" and "them" or has that line become completely blurred?

I do think that the line between us and Neanderthals — or Denisovans, for that matter — has become blurred to some extent. From a purely academic point of view, it's a question but not a particularly interesting one: what defines a species? A common definition is that members of different species can't have fertile offspring. But clearly, we could. At the same time, we see that certain parts of the genome don't contain any Neanderthal DNA, which suggests that natural selection weeded out some aspects of their genetic contribution. So, it's something in between.

I often think — what if Neanderthals had survived another 40,000 or 50,000 years? That's only 1,200 or 1,400 generations. Would we have seen even more extreme forms of racism, because they were visibly different from us? Or would it have forced us to rethink the strict divide we make today between humans and animals?

If there had been another species around, one that also used fire and tools but was clearly not the same as us, maybe we would better understand that we are just one point on a continuum with other organisms. But we'll never know.

One of the most fascinating findings in recent years is how Neanderthal heritage affects our health today — from the risk of severe COVID-19 to our sensitivity to pain. This takes paleogenetics from the history department straight to the hospital ward. Do we have more "medical surprises" in store regarding our archaic inheritance and should the future of personalized medicine take a patient's "inner Neanderthal" into account?

I do think there are more surprises to come. The biggest surprise for me was the COVID pandemic. Here comes a completely new virus and it turns out that the strongest genetic risk factor for becoming seriously ill comes from the Neanderthals. We had well over a million extra deaths globally during the pandemic due to this Neanderthal variant.

That said, the Neanderthal contribution perhaps stands out more than other mutations simply because they were separated from us for over half a million years, accumulating changes that were then reintroduced into the modern human gene pool.

What's interesting is that many of these variants were already known in medical genetics. We just didn't know they came from Neanderthals. For example, some variants affect how we metabolize drugs because they influence enzymes in the liver. If you take blood thinners — say, after getting an artificial heart valve — you're often tested to make sure you don't carry certain variants that require a lower dose. Some of those more sensitive variants come from Neanderthals. These were well-known medically, but we only recently discovered their Neanderthal origin.

So yes, this is very interesting for understanding our physiological and genetic history, but I wouldn't say it's revolutionizing medicine.

At the Max Planck Institute, you have started studying Neanderthal genes in so-called "brain organoids" (mini-brains) to see how their neurons differed from ours. This sounds like science fiction. What has been the most surprising difference in neuronal development between modern humans and Neanderthals that you have observed? Is there a specific genetic "spark" or mutation that allowed Homo sapiens to become the species that creates art and dominates the planet?

We've identified a few changes that affect things we can model in brain organoids — these are small clusters of cells, just a few millimeters across, that mimic early brain development during the first trimester of fetal life. One set of three genetic changes, working together, improves the accuracy of chromosome segregation when neurons are born. If chromosomes are missegregated, those cells tend to die. So these changes likely lead to more precise cell division and better survival of new neurons.

There's another change that actually increases the number of neurons being formed. That's obviously very intriguing. Neanderthals had brains just as large as ours, but we don't know whether they were organized in the same way. Their cellular composition could have been slightly different.

What we model in organoids is early development — we don't yet know if these differences carry over into adulthood. However, when we introduced the modern human versions of the chromosome segregation genes into mice, we did observe more accurate cell division.

So yes, it's very tempting to think these changes matter, but we don't know for sure. It's a really difficult area of study. We're currently observing those genetically modified mice to see whether their behavior or cognitive abilities differ in meaningful ways.

Genetics did not emerge in a vacuum — it grew organically out of eugenics, as practiced at the Kaiser Wilhelm Institute (now Max Planck) whose goals are appalling by modern standards. Yet today, we see Silicon Valley billionaires investing billions in biotechnology with the dream of creating "better," disease-free and longer-lived humans. What moral responsibility does this place on top-tier scientists like yourself?

I do feel a responsibility to talk about these things and especially to make clear how little we still understand. The COVID risk is a good example. If you're infected with COVID, you definitely don't want to carry a certain genetic variant because it doubles or even triples your risk of becoming seriously ill or dying. One might say, "We should just edit that away." But that same variant reduces your risk of getting infected with HIV by about 25 percent. So, if I'm exposed to HIV, I'd want to have that variant.

This shows that almost all genetic variants exert their effects in specific environmental contexts, like which viruses you're exposed to. What may seem like a harmful mutation in one context could actually be beneficial in another.

I think it's reasonable to consider genetic testing and even termination in cases of very severe monogenic diseases. But not for traits that only slightly improve your chances of surviving this or that illness.

In a way, genomics has been oversold. There's a tendency to believe we understand much more about ourselves than we really do. We mainly understand things with large effects that cause serious diseases. People hoped we would find clear genetic explanations for common conditions like high blood pressure or diabetes — things many of us suffer from. But in reality, those are influenced by a vast number of variants across the genome. If I'm honest, genetics plays a very limited role there. What we really need to do is change our lifestyle.

Your book "Neanderthal Man: In Search of Lost Genomes" is a wonderful description of the failures, contamination issues and frustrations behind the scenes. Science is often presented as a series of successes, but your work highlights the struggle. What has decades of hunting for "dirty and broken DNA" taught you about patience and error? How do you motivate your young students when they have worked for years only to find their samples are contaminated?

I think it's true in general that science is full of frustration. But I don't think that's unique — it's similar in other creative fields. If you're an artist or a composer, you face the same struggles. And we should talk about that. It's part of why doing this kind of work is both interesting and challenging.

One approach is to structure your work so that you're doing both high-risk and low-risk projects. The more predictable projects are usually less exciting, but they're more likely to yield results. The high-risk, high-gain ones are harder — they might fail completely, but if they succeed, the payoff can be revolutionary.

Having multiple projects helps. Even if your long-term goal is unlikely to succeed, there are usually intermediate goals along the way that you do achieve. It's rare for a multi-year project to be a complete failure.

In a previous interview with Novaator, you said: "Culture is much more important than our genes." Yet, you have dedicated your life to studying genes. Is there a contradiction here? Or is it a case of biology providing the "hardware" while culture is the "software" and you are trying to understand if Neanderthal hardware could have run our modern cultural software?

You can ask many, many interesting questions, but the real art lies in asking questions that are both interesting and answerable. Genetics can help us answer some of those. For example, modern human population history might help explain why we biologically react to certain things the way we do.

But for us as individuals, our cultural history is often far more meaningful than our genetic history. I sometimes say this to students: when I go to Greece and see the ancient temples and monuments, I feel deeply moved. I feel connected to architecture, democracy and all that. But genetically, my ancestors weren't in ancient Greece — they were in Estonia or somewhere on the eastern steppe. Yet, in terms of how I experience my identity and roots, culture is far more important than DNA.

We are used to thinking of ourselves as the winners of evolution — the only surviving human species. However, paleontologist Henry Gee has argued that Homo sapiens has already passed its peak and is heading toward extinction, citing our low genetic variation and habitat destruction. You have seen the genetic decline of Neanderthals up close. Do you see similar danger signs in human population dynamics today or is our "culture" the lifeboat that makes biological rules invalid for us?

I'm an optimist. What stands out to me in the history of both Neanderthals and modern humans is how incredibly adaptive they were. They found ways to adjust their culture and behavior as their environments changed. Neanderthals survived several ice ages before they disappeared and their extinction was probably caused by modern humans, not by something inherently wrong with them.

Yes, modern humans are problematic in that we're driving much of the planet's biodiversity to extinction. But I don't think humans will go extinct. We will survive. There will be challenges — there always have been — but we'll get through them.

So you think the pessimistic voices are not grounded?

Yes, I think so. It's not just paleontologists — many young people today have this gloom-and-doom outlook about climate change and the future. Yes, it's challenging. But it's not the end of humanity.

If you look back in time, there were once hippos, zebras and lions in Europe. It was much warmer then and humans were still around. We can adapt to change.

You are a prime example of how curiosity-driven, "blue skies" research — studying ancient mummies and bones — can lead to a Nobel Prize and modern medical discoveries. In Estonia and globally, there is increasing pressure on scientists to do "useful" research that brings immediate economic returns. What is your message to politicians and funders: why is it vital to fund research that might seem "useless" at first glance?

I think we need a balance. But basic research provides the raw material for future applications and economic development. Think of CRISPR-Cas9 — it came out of studying strange bacteria that live in extreme environments. There are so many examples where curiosity-driven science led to breakthroughs that others later picked up and turned into something practical.

You can't choose just one or the other. We need both.

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