Question

Read: The great opportunity: Evolutionary applications to medicine and public health. Evolutionary Applications, 1, 28-48,

ARTICLE AVAILABLE AT: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3352398/

1. Discuss why evolutionary biology has traditionally not been an integral part of medical sciences and the current thinking regarding how it actually can contribute to medicine.

2. Discuss a specific example of how there has been selection and maintenance of certain alleles that can cause a disease or a disorder.

3. Explain the consequences of a patient harboring multiple pathogens. How would a doctor draw upon the lessons from evolutionary biology to deal with these consequences?

4. What it the medical implication of the observation that many symptoms of infectious diseases are not directly caused by the pathogens but by the response of the defense mechanisms of the host and how does evolutionary biology contribute to this implication?

Answer 1

New applications of evolutionary biology in medicine are being discovered at an accelerating rate, but few physicians have sufficient educational background to use them fully.

Knowledge about evolution provides physicians with an integrative framework that links otherwise disparate bits of knowledge. It replaces the prevalent view of bodies as machines with a biological view of bodies shaped by evolutionary processes.

Several sources contribute to the recent flowering of evolutionary approaches in medicine. The first is that the basic science of evolutionary biology continues its rapid development, building on the stable foundation of Darwin and Wallace’s theory of natural selection. Genetic variants carried by individuals who reproduce more than others tend to increase in frequency over the generations, thus shifting the genetic make-up and mean phenotype of the population to be more like them and generally better adapted to their environments. The role of natural selection in shaping living organisms has been empirically confirmed beyond dispute. Selection is by no means the only factor, however. Mutations are inevitable; DNA is damaged by radiation and toxins, and replication is not perfect. Other random events are also important; genetic drift can push neutral or even deleterious alleles to high frequency, whereas a storm might eliminate all individuals with a useful mutation. Population bottlenecks, inbreeding, and migrations also shape gene frequencies, which in turn influence the distribution of phenotypes. Natural selection and these other evolutionary mechanisms change species, and, equally important, keep them the same via stabilizing selection that disfavors individuals with extreme traits .

In the area of infectious disease, for instance, long-standing recognition of antibiotic resistance has been augmented by new, sophisticated models of how selection shapes increases, as well as decreases, in levels of virulence, according to their benefits for pathogens.

Also, defenses against infection, such as fever and immune responses, are now interpreted as the products of an evolutionary arms race in which stasis is likely to be fatal and effective defenses are likely to be costly and causes of disease in their own right.

Recent evidence suggests that the benefits of modern hygiene have serious costs in lack of exposure to infections that stimulate inhibitory aspects of the immune system, thus perhaps accounting for rapidly rising rates of allergic and autoimmune disorders.

It has been known for a long time that sickle-cell trait provides resistance to malaria (the blood cells are less hospitable to the P. falciparum protozoan parasite that is one cause of malaria). This explains the persistence of sickle cell disease in populations where malaria is endemic.