Today’s guest is Professor Eske Willerslev, a world-renowned evolutionary geneticist, director of the University of Copenhagen’s Centre of Excellence GeoGenetics and holder of the Prince Philip Chair in Ecology and Evolution in the Department of Zoology at the University of Cambridge! His research spans a number of topics within evolutionary genetics, such as ancient DNA, environmental DNA and human-pathogen evolution. Much of his research also involves working with indigenous communities to better understand human history, leading to him being adopted into the Native American Crow tribe under the Indian name of “Well-Known Wolf“. He has appeared in a number of films as an expert on human evolution, such as “First Peoples”, “The Great Human Odyssey” etc, and has written a number of popular books .
What is your particular area of expertise within human evolution studies and what are your specific research interests?
My speciality within human evolution is ancient genomics, sequencing and analysing the genomes of ancient individuals to understand our demographic history. I am particularly focused on modern human history; the history of contemporary Homo sapiens. The main aim of my research is therefore to understand how we, as modern humans, obtained our genetic diversity through processes like migration and adaptation. I also do a lot of work on infectious human diseases in regard to human history.
What was your path into evolutionary genetics? What originally drew you towards this discipline?
I was educated as a biologist at the University of Copenhagen in Denmark and I actually didn’t enjoy my studies very much! There were only two modules that I really liked: evolutionary biology and human palaeontology. So, I guess biological sciences were the trajectory I initially took to get into evolutionary genetics, but it was certainly not a straightforward path to get there. During my Masters, I wanted to do DNA-based research to better understand the peopling of America — that’s what I was really interested in — but nobody in Denmark at the time did this type of research as there were no ancient DNA laboratories. There was also no interest in my Department of Evolutionary Biology to expand into human evolution. So, I started working on extracting microbial DNA from ice cores, which was very interesting but not what I really wanted to do. It was when I first became a professor, and this happened quite early in my career, that I got the opportunity to finally pursue the area of research that I wanted and I’ve done so ever since!
I think that it is not necessarily unusual to see this in science. Quite often, when you are a student, you cannot always pursue exactly what you dream and are passionate about. Instead, you gradually work towards that goal. So that’s what I did, every time I made choices that got me closer to this goal, even if they weren’t exactly what I wanted to do at that moment.
What was your PhD experience like?
Well, I don’t actually have a PhD! I started it but eventually I ended up submitting as a Doctor of Science thesis. Back when I wanted to do a PhD, there were very few around but I had been short-listed for a doctoral fellowship at my University – I was actually first on the list for this place. However, my supervisor ended up choosing another student instead of me! Of course, I was very upset at the time as I felt it was unreasonable, but my supervisor had decided on that other student because, ultimately, she was much more interested in the topic. But, I got so annoyed about not getting the fellowship that I decided I would submit my work as a Doctor of Science thesis! This is actually a bigger piece of research, where you have to provide more papers and, because I had worked really hard, I did end up having enough to submit in this format. You normally do a Doctor of Science towards the end of your career, so a lot of people thought it was very odd that I did this so early and got upset, my supervisor included as he hadn’t got a Doctor of Science… But it turned out to be a clever move in the sense that I already had a blueprint that showed I was capable of becoming a full professor, and so I achieved this just one and a half years after I did my thesis and defence.
What projects are you currently working on?
I’m working on several projects currently, but my main focus at the moment is to understand the origins of diseases susceptibility — the genetic variants associated with disease risk in humans. For example, I’m trying to understand why some people have an increased risk of mental disorders or diabetes, as well as other diseases. To look at the origins of these problems, we have to go back into history and study genomes from the past. Therefore, currently my research aims to try and uncover why we face these pathological challenges that are so prevalent today. Where did they come from? Why did they evolve? These kinds of questions.
What project are you most proud of?
I’m definitely most proud of the third or fourth paper from my career, the one that established the field of environmental DNA. This is where you take environmental samples, such as soil or water from the ocean or lakes and sequence the DNA in these samples. Through doing this, you can find out what animals and plants were and are living in certain places despite not having any macro-fossil evidence. This paper was published in Science in 2003 and, even though it’s not my most cited paper, I am very proud of it because I believe it was really original at the time. Even in incidences where I was the first to do something, like sequence the first ancient genome, these were natural progressions — someone else would have made these next steps a few years later if I had not. This paper was not like that, as it was not only one step or two steps ahead, but multiple. It took 10 years before anyone trusted this research and I actually had a few problems getting subsequent papers published because of it! My supervisor thought it was the most stupid idea he had ever heard!
Now, environmental DNA is a field that is widespread in genetics, and a lot of palaeontologists and ecologists rely on its fundamental principles, that DNA from higher organisms is present in the environment even if we can’t see it. This was a completely new way of thinking that had not been seen before — understanding that we might be walking around on DNA from the present and the past, be it from a leaf that has fallen from a tree and subsequently degraded or a dog that has left faeces on the street that has since washed away. Following this idea, I produced this paper which became the foundation of environmental DNA, and also made me more widely known in the scientific community. So yes, I’m very proud of it.
What have been your favourite and most memorable experiences of your career?
I think it has to be engaging with the indigenous communities. A lot of my research on ancient human remains have involved connecting these skeletons with their traditional owners, both in Australia and the Americas. For me, it’s some of the most interesting experiences I’ve had in relation to my work, because not only has it given me perspectives on why many of these communities are reluctant to participate in scientific research but it has also changed my own way of looking at life and indeed the world around us. I am very grateful to have had these opportunities.
What do you think has been the most revolutionary discovery in human evolution studies over the last 5 years?
This is tricky – good question! I think it’s the fact that you can obtain pathogens from human skeletons without any physical or morphological evidence for disease. This was actually a paper that we did back in 2015 in Cell where we found evidence for a plague epidemic at least 3,000 years before any other recorded epidemics. We had known that you could extract pathogens out of skeletons that have been infected and show physical signs of infection, but we also realised was that you also can obtain pathogens out of large number of skeletons showing no signs of infection; this is a real game-changer with regard to the possibilities to understanding human pathogen evolution, how they spread etc.
I think another one would be the work that has been primarily been done by my colleague, Enrico Cappellini, who has found a way to sequence enamel proteins to investigate evolutionary questions about the deep past — now known as the field of proteomics. I’ve been on some of these papers but others have primarily been driving this new wave of research. The first foundational paper was published just this year, and allowed us to investigate the evolutionary relationship between Homo antecessor and other hominin species. I think proteomics has powerful potential for understanding hominin evolution way further back in time than we are currently able to do with aDNA.