Darwin’s Reach: 21st Century Applications of Evolutionary Biology

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Darwin’s Reach: 21st Century Applications of Evolutionary Biology by Norman A. Johnson

This book is about applied evolution – the application of the principles of and information about evolutionary biology to diverse practical matters.


To some extent, applied evolution has existed for an exceptionally long time. The reciprocal exchange between evolution and the applied science of breeding animals and plants literally started with Charles Darwin, the pigeon breeder and author of Variation Under Domestication as well as The Origin of Species. This exchange continues to present day; for instance, evolutionary geneticists are developing statistical models that take advantage of the tremendous power of complete genome sequences to determine how breeding designs would improve livestock. From time to time, earlier generations of biologists applied evolution to some aspect of human health. The notable mid-20th-century contributions Peter Medawar and George Williams made toward an evolutionary theory of aging quickly come to mind. Yet these early efforts have been piecemeal; there was little coherence across these applications until fairly recently.


Applied evolution of today differs from that of the nascent attempts of yesteryear, both in being more coherent and in having a much wider scope. In the 1990s, George Williams and Randy Neese, followed by others, developed Darwinian (evolutionary) medicine, applying the principles of evolutionary biology to the broader question “Why do we get sick?” In the time since, evolutionary medicine is becoming a separate discipline, with its own various institutes, centers, and journals. Today’s applied evolution is more than just evolutionary medicine and agriculture. Evolution also is being applied to environmental concerns: Which of these different populations of a beetle likely to go extinct, and how can we best conserve them? Is this species of sea urchins likely to be able to adapt to the changing environments arising from global warming? Evolution’s reach extends still further. It now also includes forensic biology and the law, as its principles are being used in criminal and civil court proceedings. Ideas from evolutionary biology can be used to inform policy regarding foreign affairs and national security. For instance, the evolution of large horns in some beetle species shares an underlying framework with the arms races between nations that have led to dangerous escalations of weapon stockpiles.


This last decade has given researchers two game-changing tools and a major shift in thinking that pervade much of biology. First, high-throughput sequencing has drastically increased the speed at which DNA sequences can be generated and opened up research to any organism on the planet. Coupled with advances in computation, high-throughput sequencing is changing how many evolutionary biologists conduct their research programs. They can now address topics that were only contemplated a decade ago. For instance, consider the Neanderthal genome studies. Biologists not only can conclusively demonstrate that we interbred with Neanderthals, but they can estimate how much Neanderthal DNA individuals have. They can even infer the action of selection at particular parts of the Neanderthal genome that came into our own. These sequencing advances are important not just to biologists; in addition, they have also reduced the price tag to the extent that getting one’s genome sequenced is within the budgets of middle-income people. Already, millions of people have had parts of their DNA assessed through consumer genomics kits to infer their ancestry and/or to assess their risk of obtaining a disease. Knowledge of evolutionary biology informs both ancestry genetic tests and disease risk. The principles of evolutionary biology also underlie the methodologies used to map disease and other traits to genetic variants.


Perhaps even more importantly, the editing tool CRISPR/Cas9 allows researchers to alter gene sequences specifcally and with relative ease. CRISPR editing already is empowering researchers who are interested in the gene function for just about any organism. These scientists can address questions such as which sequence changes will cause their organism of choice to have greater tolerance to drought. This technology is also being developed to control pest species. Evolutionary principles are important in ensuring that such measures are safe and effective.


As high-throughput sequencing and CRISPR genome editing are the tools of 2010s biology, the concept of the decade is the microbiota. This is the collection of microbes – bacteria, archaea, fungi, and viruses – that live on and within the bodies of larger organisms, including humans. Recent research shows that the microbiota is dramatically more important to our health and even our behavior than what was thought even a decade ago. We really are ecosystems, and as such, ecosystem ecology and evolution are of essence to the study of our health. Recent research is also showing that the microbiotas of other organisms are also important to their ability to respond to challenges.


In addition to these new technologies and discoveries, we face challenges new and old. Global climate change has intensifed over the last decade. The principles of evolution are central to addressing whether organisms can continue to adapt to rising temperatures and increasingly acidic oceans. Other human activity has placed a large number of species in peril. While the looming extinction crisis is grave, it is not hopeless. Evolutionary biology—combined with ecology and genetics—is vital to these essential conservation efforts. The COVID-19 pandemic has reminded us of the power of infectious disease to cause misery and death. Here, we will see how evolutionary principles are used to track the spread of viruses and develop vaccines. Evolutionary biology has also been vital to the development of drug regimens to treat HIV-AIDS.


The application of evolutionary biology also entails possible misapplications wherein science is perverted to justify dubious or even evil ends. The most extreme historical examples include Lysenko’s perversion of genetics for ideological goals in the Soviet Union and the use of evolution to justify genocide, brutality, and “racial” superiority in Nazi Germany. But there are less extreme versions of such misapplications, some of which persist today. For instance, some authors have misused information about genetic variation among human populations to make unsubstantiated, racist claims. These misapplications do not need to arise from nefarious motivations. The much-hyped paleo diet, regardless of its health benefts, is not well supported by the evidence about what our ancestors ate and the speed to which we can adapt to dietary changes.


In addition to informing various audiences about the importance of these evolutionary applications, I hope this book encourages dialogue among different researchers studying different evolutionary applications, with the aim of a better understanding of the nascent science of evolutionary applications. Perhaps, in the not-too-distant future, such dialogue may lead to mutual illumination across the disparate branches of this young feld. Perhaps lessons learned in a research program using evolutionary approaches to better treat cancer could then be transferred to research in attempts to halt the spread of an invasive species, such as the cane toad.


In thinking about evolutionary applications as an emerging feld, I see at least three main types of evolutionary applications. First, investigating the evolution of an organism is useful because that organism’s biology matters to the practical problem. For example, determining whether a doctor accused of infecting his partner with HIV samples from a patient depends on learning about the evolutionary relationships of the partner’s viral load among other viral samples. Another type of application involves searching for parallels between an evolved system and an aspect of human culture. An example is similarities between arms races in conf icts between human societies and arms races that occur within and between nonhuman animals. The third type of application, which is central to evolutionary medicine, is viewing human health from the perspective of human beings as evolved organisms that live within an ecosystem.


Applied evolution is not only interdisciplinary but also multidisciplinary. Consequently, no one can be an expert on all of the felds related to applied evolution. This book is for experts in one feld that pertains to applied evolution who are interested in other aspects. It is also for students at the undergraduate and graduate levels. It is they who will most likely forge and deepen the new connections. Finally, the book is for the nonexperts, the general readers, who are interested in following how evolution affects their lives. One of the public relations challenges that evolutionary biology faces is that most people do not see it being all that relevant to their daily lives. Even many who accept evolution do not grasp how far Darwin’s reach goes. I hope to help change that perception with this book.


This book is divided into four sections (in order): Health, Food, Environment, and Society. The arrangement is somewhat arbitrary; each section can be read independently of the others, though chapters within sections will build on one another. Due to space limitations, not every subject affected by evolutionary applications can be covered. For instance, I will not cover much about the exciting work in uses of evolutionary principles in computation. Although several chapters will discuss the microbiota, no one chapter will be devoted to it.


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