Report from the November 10 Evolution and Medicine Symposium in Berlin

Nicole Bender, from the Zurich Institute of Evolution and Medicine, has written the below summary of the November 10 symposium, “The Evolution of Medicine to Evolutionary Medicine” organized at the IRI Life Sciences (Humboldt University), by Detlev Ganten, World Health Summit President, Randolph Nesse from Arizona State University, and Peter Hammerstein from Humboldt University, with assistance from Stefanie Scharf and Jörg Heldmann. The Symposium took place in the framework of the “Interdisciplinary Dialogue” at the IRI Life Sciences, a series funded by the Schering Stiftung.  he symposium was organized in conjunction with The Falling Walls Conference.

After a general introduction by Randolph Nesse, six German researchers presented their ongoing projects. Interestingly, most of them work in the field of immunology, complementing each other in a fruitful way. John Baines from the Christian-Albrecht University in Kiel studies why potential detrimental genetic variants can be maintained by balancing selection, choosing the example of blood group polymorphisms. Using a mouse model, he showed that gene variants leading to the bleeding disorder von Willebrand disease are maintained because they influence the microbiome of the mice in ways that reduce their susceptibility to infectious diseases. This advantage seems to be more relevant than the danger of prolonged bleeding in the case of an injury.

Rainer Straub from the University Clinic Regensburg explained how genetic variants that increase the risk for chronic inflammatory systemic diseases can represent a trade-off between immediate health benefits and long-term detrimental effects. He showed several examples of gene variants that increase the risk of autoimmune diseases on the one hand, but reduce the susceptibility to infections on the other hand. Interestingly, some of the genetic variants predispose to detrimental effects, like vitamin D deficiency. So where is the benefit of those genetic variants? Straub showed that in some cases, the benefit lies in saving energy, for example in reducing all activities of the organism, including feeding activity. What in the short term is beneficial (saving energy) can be detrimental in the long term (lack of vitamin D).

Another aspect of the evolution of the immune system was presented by Joachim Kurtz from the Westfälische Wilhelm Universität in Münster. Kurtz focused on the host-parasite co-evolution which represents a continuous reciprocal evolutionary arms-race, also known in biology as the Red Queen hypothesis. If parasites are missing in a modern environment, a host’s defence mechanisms can lead to diseases, like autoimmune diseases or allergies, the so called hygiene hypothesis. Another interesting point discussed by Kurtz is the parasite manipulation of host behavior. What was shown to date in selected examples in nature is an interesting idea if applied to humans. Can it be that our pathogens manipulate our behavior in their favour? To date we have only few examples in humans, like the infection with Toxoplasma gondii that leads to a prolongation in reaction time and therefore to a higher susceptibility to traffic accidents. In this respect, a question from the audience was very interesting, but had to remain unanswered at the moment: what about sexually transmitted infections?

A further example of trade-off in the evolution of the immune system was presented by Tobias Lenz from the Max Planck Institute for Evolutionary Biology in Plön. Lenz studies the genetics of the MHC and HLA system, which is known for his ample allelic variance in the human population. This allelic variation allows for rapid adaptations of the immune system towards a large number of pathogens. However, as Lenz pointed out, in a single individual the variety of these variants is limited. Why? Wouldn’t it be beneficial for each of us to have a large amount of different MHC or HLA variants to fight infectious diseases? Unfortunately this is not possible, as these genetic variants predispose to autoimmune diseases, so a major evolutionary trade-off is involved. Interestingly, this trade-off seems to depend on pathogen density in a given region. This could explain the different prevalence of autoimmune diseases in different parts of the world.

Not only the immune system is studied in Germany from an evolutionary point of view, but also topics related to human behavior. Peter Hammerstein from the Humboldt University in Berlin discussed the parent-offspring conflict using the example of weaning. From the mother’s perspective, resources should be distributed equally among all living and future offspring, with no preference for a single individual. The offspring’s position is diametrically opposite, as it has an interest in obtaining the most resources for itself. For this reason, begging for food, competing with siblings, and manipulating the parent in order to receive more resources are selected for. How strong this selection can be is shown with the example of chicks that beg loudly for food, despite attracting the attention of potential predators. This generational conflict is actually an example of evolutionary intragenomic conflict, as within a single individual there are parental genes and offspring genes with different interests. An example in humans is diabetes in pregnancy. While the mother optimizes the flow of glucose to the embryo through the placenta to maximize her fitness, the embryo produces hormones that give it benefits by increasing blood glucose levels, at the cost of diabetes in the mother. Similarly, foetal cells can immigrate into the mother’s tissues; migration into the thyroid gland can cause hypothyroidism in the mother, prolonging interbirth intervals, perhaps benefitting the child.

A different aspect of the evolution of human behavior was presented by Martin Brüne from the Ruhr University in Bochum. Brüne investigates the evolution of psychiatric disorders, using an evolutionary methods toolbox that includes comparative evolution, genetics, game theory, life history theory, and ethology. One example is the detrimental effect of child neglect or child abuse. Persons who experienced such neglect are at risk for borderline syndrome. Treating them with oxytocin (a hormone which is involved in social bonds) can reduce their flight reactions, but does not increase their affiliative behavior and even reduces their trust towards other people. Brüne explained these effects by brain changes inflicted by neglect in childhood, discussing different kinds of damage depending on the age at which the neglect or abuse happened. It seems that the brain of affected children tries to adapt to function in a hostile world. This could also be the explanation why genetic variants increasing the risk for psychiatric disorders like ADHS are present. Depending on the environment, such disorders could be positive for survival.

The presentations in this symposium show not only the vast varieties in topics and approaches within the community of evolutionary medicine in Germany, but the field’s international reach. Evolutionary medicine is constantly expanding both its research areas and discipline fields, and its geographical distribution, especially in Europe. This means that the definitions and the aims of evolutionary medicine might change over time or depend on the geographic region. A particularly fruitful development is the shift from a mostly explanatory focus to a more applied focus, especially in medical practice. Many realistically hope that a breakthrough made possible by evolutionary medicine research will bring the field to greater public attention. The high quality of research presented at the Berlin symposium, the expanding network of involved international researchers, and the research results approaching more and more clinical application, increase optimism that such breakthroughs may be imminent.