Carles Lalueza-Fox: "There do not exist the 'genes of evil', but rather a genetic basis and an environment"

Some seek their roots to try to understand who they are. Carles Lalueza-Fox (Barcelona, 1965) searches for them to decipher where we come from and better understand our past as a species. For more than two decades, this paleogeneticist from the Institute of Evolutionary Biology (IBE-CSIC-UPF) and current director of the Museum of Natural Sciences of Barcelona has been reading the history of humanity in ancient DNA and is one of the world's leading experts. He has contributed to demonstrating that modern humans carry Neanderthal DNA and has reconstructed migrations and interbreeding of prehistoric populations. He has just published Identidad (Crítica) where he delves into swampy terrain: what DNA can explain about who we are and what it cannot.

You dedicate almost 300 pages to explaining what DNA tells us about who we are. Have you already discovered who you are?

— Not really. People tend to think that, amidst all the personal and world confusion, their genes will finally tell them who they are and they will stop suffering. There are even private companies that have become fashionable in the United States and other countries that sequence your genome with the promise of telling you who you are. There are people for whom being told they are half Viking gives them a bit of personal prestige. But the meaning of our life will not be found in our genes, nor in our genealogies, nor in our population. Genetics has answers, obviously, the thing is that often the questions we ask it are not the right ones.

What does genetics allow us to know about ourselves?

— It connects us with very distant ancestors. Knowing that we have 2% Neanderthal DNA is truly incredible because it links us to someone who lived almost 50,000 years ago. It also allows us to find connections with people from the past who will be our direct ancestors. At the same time, however, all this information must be contextualized, because our genome, as we go back into the past, is fragmented into millions of pieces, probably scattered all over the world, and it makes no sense for us to focus on a specific ancestor. The same happens if we look forward: if you want to imagine what will become of you in the future, be clear that in a few generations your genes will also be scattered, even if you haven't had children, because it only takes a cousin to have had them. And your genome will move forward into the future like a kind of puzzle, disseminated in thousands of pieces.

How can it be that on the other side of the planet there is, probably, someone just like me?

— The doppelgänger phenomenon! In 2022 I participated in a very fun study, which unfortunately has not been repeated, where a photographer would post photos on a website that people sent him of lookalikes, people who had nothing to do with each other and looked very much alike. Beyond the humor, the initiative had a scientific interest: to wonder exactly why it happens. One hypothesis was to think that they were very distant family and that, therefore, they shared certain genes. This is the part that I was in charge of to rule out that they were not distant cousins, sixth cousins, eighth cousins, whatever it was. And no, they were not.

And then?

— They shared many genes involved in facial morphology. There are no genes that make you have one nose or another, but rather a whole set of genes, about 200, that intervene a little in facial morphology. And, therefore, since it is a large number, but it is finite, if humanity is already 8 billion people, you really end up with a very high probability of ending up having some double somewhere. And they were not only similar in this facial morphology, but curiously in a lot of genes that have been described as associated with behavior or hobbies, or type of diet, smoking, sedentary lifestyle, et cetera. So they also resembled each other in things that went beyond appearance.

You explain the case of a great-niece of the Nazi Hermann Göring, Hitler's right-hand man, who decided to get sterilized so as not to have children and thus avoid passing on the “genes of evil” to them.

— An erroneous decision! Not only because she shared only 25% of the genome with Göring, and if she had had a child, this one would have only shared 12.5% of genes with the Nazi, but also because he, in another context, would probably have been a different person. I am not saying he would have been a great member of the community, because he was clearly egomaniacal and narcissistic, but if instead of having been born in that interwar period he had been born a hundred years later, in another educational and environmental setting, he would have been another person. By this I mean that there are no genes for evil, but rather there is a genetic basis and an environmental setting. We could compare it to height: we have between 100 and 200 genes related to height; you may have the potential to reach a certain height, but if in your childhood you have nutritional deficiencies, you will remain short.

With the rise of the far right everywhere, collective identities are once again very significant.

— Putin, to justify the invasion of Ukraine, gave a speech where he mixed sharing a common linguistic base, because both Russian and Ukrainian are Slavic languages, with sharing the same genetics. It is erroneous. If you want to create a sense of collective, you can probably work with shared cultural ideas without needing to get into shared genetic heritage. Football teams are clear about this: what matters is being on the team, not what color your skin is. If you are from Liverpool, your family is the other Liverpool supporters.

Trump and the Western far-right is a firm believer in the great replacement theory, which maintains that immigration is eliminating our identity.

— There is no genetically isolated population. All of them are mixed to a certain extent. In paleogenomics studies, we see the prevalence of constant migratory phenomena since prehistory, which creates layers that overlap. All populations share these layers, perhaps in different proportions, but there is no such thing as genetic uniqueness.

And yet, we continue to link identity to genetics. Why?

— Our sense of identity is like a story of the past that we have created. Throughout life, we keep reformulating not only who we are, but also what we are doing here and how others see us. For some people, discovering part of their genetic heritage can provide an answer they consider satisfactory, but it is totally subjective. We have many more genealogical ancestors than genetic ones, who are the ones that have effectively given us something in our genome. We may be tempted to think that genetic ones are more important than genealogical ones, when in reality you may have been influenced more by a person from your genealogy, such as an uncle by marriage, than by some genetic relative.

This will be especially interesting in children born from gamete donation.

— Yes, usually at some point these people feel the need to find their biological family, because they think that then they will be able to understand themselves better, when perhaps they have been raised all their lives by another family, which is who has shaped them as people. Despite this, there is this idea that "I am another person" and that, "if I could know who my biological mother was, I would understand myself".

Some of his studies have been controversial.

— A research of mine about the Balkans generated a lot of controversy, yes. In that region, some countries speak languages originating from quite late Slavic migrations, framed within the great migrations after the Roman Empire. When we analyzed the genome of that period from that region, we found that the Slavic migrations permeated the entire Balkans and even reached Greece. Although Serbs perceive themselves as relatives of the Russians, that ancestry was also found from Romania to Croatia and Greece. And this generated criticism in one direction and the other: from people who accused me of promoting Pan-Slavism to Serbs who refused to accept that this ancestry was shared with the Croats, whom they consider their enemies.

Could you have imagined, when you started working in paleogenomics, that you would end up identifying with precision migrations, but also social structures or even families and marriages from thousands of years ago?

— Not at all. All of this has been possible thanks to a technological revolution that began in 2008. By 2010, the first three ancient genomes were published, and it is estimated that this year we will reach 15,000. Imagine that! An area where many efforts are currently being dedicated is the study of diseases of the past, because when you sequence a person you can know all the pathogens they had.

Neanderthals are an example of how genetics has changed our perspective.

— The list of genes that are different between humans and Neanderthals is around 100, a ridiculous amount. Among these, you also won't find one in particular that allows you to say “this is what makes us human”. Clearly, it is a differentiated population, but at the same time genetically very similar and with a large overlap. When we interbred with them, leaving Africa, we inherited a set of genes that worked very well for us to adapt to Eurasian conditions. Probably, genes involved in resistance to pathogens that our African ancestors did not know. Although now many of these genes are harmful, at that time they served to help us adapt much more quickly. In fact, the success of our species, which in a few millennia expanded from Africa to northern Europe and Oceania, a huge geographical range, comes from this inheritance from the Neanderthals. Therefore, however we may want to see them, at the very least we should be grateful to them.