Has evolution changed? Asking experts how Darwin's theories hold up in modern science
"Reading Darwin even today, one is struck by how effortlessly he 'filled the blanks'"
Curiosity about the diversity of life has existed throughout human history. While ideas around species evolving through time were around before Charles Darwin, evolution was only established as a field of study with the publication of On the Origin of Species in 1859. Much has changed since: the laws of heredity have been established, DNA was found to be the hereditary molecule, the genetic code was deciphered and genome sequencing became common.
Massive asked three evolutionary biologists — Harmit Malik, Isabel Gordo, and Catarina Pinho — about their perspectives on the origin of the field, what has changed, and about the future and challenges ahead.
Malik is a professor of evolutionary genetics at Fred Hutchinson Cancer Research Center in Seattle. Gordo is a Principal Investigator at Gulbenkian Science Institute in Portugal, and Pinho is a Researcher at the CIBIO-InBio at the University of Porto, Portugal.
While their viewpoints are different, they agree on how Darwin’s work was revolutionary at the time and is relevant still today, even though the nature of the research and the methods used today did not exist back then. These interviews, conducted over email, have been edited for clarity.
Rita Ponce: From where we stand now, how do you see Darwin's work? And what about his legacy and how important his work was for the development of the field?
Pinho: "I guess there is nothing that I can say about Darwin that has not been said before: how ground-breaking his views were; how amazing it is the way he imagined the processes of evolution even not knowing how heredity worked; how some of his considerations on the nature of species are still shared by many evolutionists today.”
Pinho works on speciation, the process by which new species arise, a theme central to Darwin’s work.
“I am particularly amused how [Darwin] points out that there is not a big distinction between varieties and species, because I face these uncertainties (which are part of what has been called “the species problem”) in my everyday work. I work mostly with a group of lizards that include many closely related forms, and in some cases this involves trying to decide whether or not these different forms are true species. This is a really difficult question because we are trying to impose discrete boundaries on the outcomes of a continuous process, and Darwin was quite aware and vocal about this difficulty.
Malik: I think Darwin's work is foundational to all ensuing fields of evolution, even molecular evolution. It provided a framework, a guiding principle to examine the role that natural selection plays in shaping genes and genomes.
Malik studies molecular evolution, the study of the changes that happen throughout generations at the level of DNA, RNA and protein molecules, and is mostly focused in conflicts caused by the “interests” of different genetic elements of the genome to increase their frequency.
Is it possible that Darwin would have been able to incorporate the molecular viewpoint if DNA and Mendelian genetics were [known to him]? I would expect so. Reading Darwin even today, one is struck by how effortlessly he 'filled the blanks' of what must be the mode and mechanism of inheritance, despite the fact that these were not even discovered by science by then. This is truly the hallmark of a genius.
Nevertheless, Darwin was first and foremost a naturalist. It is hard to imagine him giving up his life of voyage and adventure to pursue his ideas in a laboratory (like many of us do today).
Since Darwin’s time, much has changed in science, with new knowledge and new techniques. How do you see this change? Can you think of examples of original thesis in evolutionary biology that have been challenged/supported/refuted with new techniques and new knowledge?
Gordo: I am sure that some of the original ideas that the founding fathers of evolutionary genetics made will need some update in the face of increasing data provided by the new sequencing capacity. But I seriously doubt that the pervasiveness of natural selection, and in particular purifying selection, [the type which eliminates variants with deleterious effects] that Darwin so clearly exposed, will ever change.
Pinho: The biggest technical change I have seen in my time was the revolution in sequencing techniques, that allowed us to move from the study of a few genes that we hoped were representative to easily obtaining full genomes. We have definitely entered an era of big data in evolutionary genetics, and this has revolutionized our ability to link genotype to phenotype, for example, and to understand the complex interplay between different evolutionary forces.
In my view, many of the hot debates around evolution during the 20th century — regarding for example whether evolution was largely neutral or driven by selection; whether speciation tended to happen more in allopatry or sympatry; or whether evolution occurred in bursts or in a steady pace, for example – are outdated. What we see now are examples of all kinds of evolutionary patterns across organisms and even across the same genome, and it is very difficult to generalize and describe an evolutionary norm. One thing that has definitely not held the test of time is the idea that hybridization between closely related species is infrequent. In this case, the more we look the more we find this as a rule and not as an exception.
Malik: In the field of molecular evolution, one idea that is slightly at odds with Darwinian views is that of neutral selection; that traits can evolve even in the absence of apparent selective advantages. This view requires more knowledge about DNA and genetics, and the impact of mutation.
One other viewpoint that Darwin could not have appreciated was the role of horizontal gene transfer [movement of genetic bacterial between individuals] in shaping genetic novelty. This meant that rather than invent their own solutions in the face of selective challenges, organisms could simply steal these solutions from others. A good example is bacteria exchanging plasmids bearing cassettes that carry antibiotic resistance. Another example that almost borders on science-fiction is that there are genes in our own genomes that were stolen from viruses to provide function. These are views that have emerged from deep analyses of genome sequencing which was of course unheard of in Darwin's era but is now routinely carried out in high schools in some parts of the world today.
How do you imagine to be the future of evolutionary biology and of molecular evolution? Can you maybe reflect on that a little bit?
Gordo: My main wish for the future of evolutionary biology is that it is taught at high schools. That fortunately is already happening in Portugal. I do also hope that this subject is given the importance that other subjects have in the biology degrees in every university. Biology will not advance as fast as it should if that does not happen.
Malik: The ease of genome sequencing means that we can identify hallmarks of natural selection based solely on their footprints within DNA sequences. This has opened the door to widespread analyses of the impact of such natural selection. I am particularly excited that over the past ten years, genetic techniques have become so powerful that we can recreate evolution dating back millions of years in the laboratory and understand genetically and biochemically what forces have led to the current day.
Surprisingly, despite the power of these ideas there are many parts of the world where Darwin's life and his ideas are not routinely taught in schools. The divide between this scientific understanding of how evolution works and deeply held beliefs is difficult to reconcile for many. But it can have devastating consequences for public health officials and the public to not pay heed to these ideas. The rapid spread of the SARS-CoV-2 virus and the recent emergence of many kinds of escape variants that are even more infectious (and deadly) is a sobering reminder that evolution is always at play, whether we 'believe' in it or not.
Pinho: As I mentioned before, I truly believe that evolutionary biology has entered the era of big data and, as much as in other sciences, this brings both opportunities and challenges. We need better models and better tools to be fully equipped to handle the vast amounts of data (of all sorts: genomic data, image data, remote sensing data, time series data, just to name a few) that are being currently generated. I thus think that the future of evolutionary biology involves a lot of methodological innovation to make the best use of these data.
On the other hand, we are facing unprecedented global crises that, more than ever, have shown the critical relevance of evolutionary biology in current times and in the future answers to these crises. This has been exemplified by the race to halt biodiversity loss due to global change, by the widespread threat of bacterial antibiotic resistance, and, quite obviously, by COVID-19 pandemic dynamics. All of these challenges show the applied and essential side of evolutionary biology, and I believe a lot of research will be devoted into these avenues in the future. At the same time, such challenges have highlighted a deficit in evolutionary literacy by the general public, which I believe evolutionary biologists need to be committed to address and solve.