Nesse and Stearns on How Evolution Is Used in Medicine

I've recently written a couple of posts about how evolution is used in medicine. Randolph Nesse and Stephen Stearns in Evolutionary Applications have written an article about evolutionary medicine. Here's one part that provides some additional examples (italics mine):

Some of the most useful applications of evolution often do not use evolutionary theory directly; instead they use technologies developed by evolutionary biologists. In particular, methods for reconstructing phylogenies are being applied to genetic data with very practical results. HIV is especially susceptible to such methods because its fast-accumulating mutations create finely detailed phylogenies. For instance, certain cases of HIV could be traced back to a specific Florida dentist (Ciesielski et al. 1992). Phylogenetic analysis also was used to falsify the hypothesis that HIV was introduced into Africa via polio vaccine (Weiss 2001). The SARS epidemic was traced quickly to a corona virus similar to one endemic in bats (Li et al. 2004; Skowronski et al. 2005).

Tracing pathogen phylogenies can be very useful. Influenza phylogenies suggest which strains are likely to spread in future epidemics (Bush et al. 1999; Ghedin et al. 2005; Smith 2006), information vital to decisions about vaccine design. The current H5N1 avian influenza pandemic appears to have originated via reassortment between avian influenza strains circulating in eastern Asia (Li et al. 2004).

Public health now uses such methods routinely to trace the source of contaminated foods [Mad Biologist: Ahem]. These phylogenetic methods have a remarkable reach, back even into prehistory. For instance, the complete genome sequence of the severely pathogenic Shigella flexneri reveals that it is phylogenetically indistinguishable from the Escherichia coli that lives normally in the human gut (Wei et al. 2003). The difference seems to be in a few virulence factors that result in substantially different ecological niches for the two organisms [Mad Biologist: I told you].

Technologies for tracing phylogenies have ready application to antibiotic resistance and to pathogen evolution in general. They are particularly powerful in revealing the origins of emerging diseases. For example, HIV1 originated in chimpanzees in Central Africa, and HIV2 originated in sooty mangabeys in West Africa (Heeney et al. 2006). Importantly, these species do not develop AIDS.

Phylogenetic methods have also found recent applications in cancer research and treatment. Cell lines differentiate as mutations accumulate, and the genetic differences make it possible to trace the sequence. Two tumors that are histologically identical can have very different proteonomic signatures that make it possible to assess the level of cellular differentiation (Abu-Asab et al. 2006). Whether a tumor is all derived from the one line of cells, or from different origins arising during the tumor's growth may also be an important indicator (Merlo et al. 2006; Frank 2007).

Researchers in every area of medicine use phylogenetic methods to analyze genetic data. Sometimes they are used in conjunction with evolutionary theory, but they are also used independently to construct phylogenies with new applications in an era of genetic medicine. Doctors who understand these phylogenetic methods and the evolutionary biology behind them will be better prepared to judge the significance of research findings such as those summarized above.

The article is actually accessible to non-scientists. I recommend reading it.

Cited article: Randolph M. Nesse, Stephen C. Stearns (2008) The great opportunity: Evolutionary applications to medicine and public health
Evolutionary Applications 1 (1) , 28-48 doi:10.1111/j.1752-4571.2007.00006.x