Published: 23.02.09
Dossier Darwin

Thinking in populations

150 years ago the British scientist Charles Darwin published his famous book “On the Origin of Species”, which shook many people’s philosophy of life and forms the foundation of biology right up to the present day. Paul Schmid-Hempel, Professor of Experimental Ecology, explains in an interview what has remained preserved of the original Theory of Evolution and which modern branches of research have developed from it.

Peter Rüegg
Paul Schmid-Hempel, Professor of Experimental Ecology (Photo: P. Rüegg / ETH Zurich)
Paul Schmid-Hempel, Professor of Experimental Ecology (Photo: P. Rüegg / ETH Zurich) (large view)

ETH Life: The Darwin Year has begun, everyone is talking about the natural scientist and he has become a posthumous media star. Did you expect such a big response?

Paul Schmid-Hempel: No. I thought few people would want to get their fingers burnt on the topic. I am absolutely astonished at the big response the Darwin Year is now arousing throughout the world.

How do you explain the popularity of Darwin and his Theory of Evolution?

The subject of evolution moves many people. Even those who are not familiar with Darwin’s name know that evolution affects the view of the world and can literally be a matter of life and death. From a biologist’s point of view Charles Darwin is a towering figure of the 19th century who is still highly respected even today. He laid a foundation that has endured. He lived the “way to do science” in a way that only very few people at that time did. He pursued the scientific approach steadfastly: initial concept, evidence, critical assessment of ideas; rejecting the incorrect; accepting what is compatible with the concept. This contributes to the fact that he has remained popular and important up to the present day.

What abilities marked him out?

He had a series of talents, for example a gift for exact observation and extreme meticulousness. He had the outstanding ability to link facts together in a theoretical concept. He was also well-to-do, so he had no need to spend time looking for funding. He also had a natural ability to appeal to people and to motivate them to collaborate. As a result he obtained data and was able to discuss his results with others. Much of it took place at a distance by letter.

Which of Darwin’s ideas are still correct today?

The core thesis is still as valid as ever: variation, overproduction, selection and inheritance, which leads to adaptations. The important aspect is that these mechanisms take place in populations. However, this “population thinking” continues to cause many people great difficulties, even though it is actually rather simple. Another of Darwin’s major legacies is that he harnessed comparative research into the service of evolution. We still stand on this foundation today. Moreover that is true for all the ramifications of his work.

In which respects is Darwin’s teaching outdated?

His ideas about inheritance are totally out of date. He was also unable to explain it with the theories at that time, which is why he was severely criticized. He needed boldness to publish his theories and to acknowledge this difficulty without having any solution to offer. Gregor Mendel was the first to show that heredity takes place in “particles”, now called genes, which is what preserves variation and makes it accessible to selection.

Darwin was also misunderstood and his theory abused. Wherein do the abuses and misunderstandings lie?

The theories of Herbert Spencer, among others, gained impetus a few years after Darwin published “On the Origin of Species”. For example this movement expressed the concern that the lower social classes reproduced to a greater extent than the upper classes. It was said that medical care and soup kitchens also helped the less fit to survive. That was the core of Social Darwinism. However, Darwin always held the view that it is not just a question of naked survival, and that evolution also produces sympathy and social competence. This is why he felt it was an incorrect interpretation of his ideas.

Which other misunderstandings lurk in people’s minds?

One misunderstanding is that “fittest” means “strongest”. Darwin always used the word “fittest”, which need not necessarily be the strongest but might also be the most cooperative, for example. Another big misunderstanding is that evolution is determined solely by chance. Chance only generates the raw material – the genetic variation within a population – for selection, which is the real driving force of evolution. Evolution is probabilistic, not deterministic. Even if someone has a “good” gene, there is absolutely no guarantee that this individual will survive, only an increased probability. Yet another misunderstanding is that evolutionary processes take millions of years. In fact some of them develop very quickly, such as resistance to antibiotics.

Although much depends on probabilities, there are no calculations in Darwin’s works. Why not?

He was not a good mathematician. This is why there are no real quantitative considerations in his works. Quantification is the language of modern evolutionary research. Darwin understood the mechanics of evolution but was unable to express it in mathematical ideas even though differential calculus and probability calculus already existed at that time. The tools were actually available. I am amazed that he did not use them.

Has quantification distanced modern evolutionary research from Darwin’s theory?

Modern evolutionary research adheres firmly to Darwin’s fundamental principles. However, the biggest development has been the integration of genetics at every level of Darwin’s teaching. Evolutionary research will experience a big impetus in the next few years, thanks to new technologies such as Next Generation Sequencing with which genes can be analyzed down to their individual modules relatively inexpensively. It will become technically possible to see changes directly at the genetic level on the spot, i.e. in the field. Mathematical treatment, model-building, will also progress further. Population genetics also plays an important part. It allows us to follow genetic processes with great precision, including predicting how gene frequencies must change based on selection factors. One should also not forget the further development of the theory of evolution in the nineteen-sixties by Bill Hamilton. He made a new link between genetics and the phenotype through the concept of Inclusive Fitness. This provided clarity as to what is the essential currency in evolutionary events, namely the various different gene variants. It was also realized that passing on gene copies is important. This put Darwin’s theory on a comprehensive footing that is the essential makeup of modern evolutionary research today.

What are the evolutionary researchers at ETH Zurich working on?

Work at ETH Zurich focuses on what is known as micro-evolution. This is concerned with changes in populations, for example antibiotic resistance, and the question of adaptations. For example there is a desire to know what advantage higher recombination rates have, the size of the fitness costs for the immune response and which environmental factor causes which kind of evolution and/or adaptation. There was less emphasis on macro-evolution work here, i.e. the question of which processes lead to speciation, but that will return. Research is looking more intensively for genes that cause reproduction barriers between populations so that new species come into being. This really brings us back Darwin’s original question, which gave rise to thoughts mainly on the subject of species formation.

An eventful Darwin Year

Charles Darwin and the Theory of Evolution dominate the whole of 2009. In this connection various institutions of higher education, museums and Life Science Zurich are organizing a series of public events and campaigns. It climaxes in an exhibition entitled the “Tree of Life” from 4 to 6 September in the station concourse of Zurich’s main railway station. An interdisciplinary course of lectures on the topic of evolution will take place beginning on 17 September and the annual Latsis Symposium at ETH Zurich, again on the subject of evolution theory, will be held on 23 and 24 November. The complete program for the year, constantly updated, can be found at