Of what value is evolutionary biology in medicine?

April 3, 2009 • 9:43 am

I have sometimes written that evolutionary biology doesn’t have much practical value in medicine or other areas impinging on humanity’s material well being.  Here is one example of what I’ve said.  However, my friend and colleague David Hillis at The University of Texas in Austin — who played a big role in trying to make the Texas State Board of Education teach real science —  has taken exception to my view.  I asked him to let me know how he thought that evolutionary biology had been of use in medicine, and he wrote me an email with his answer, which he’s given me permission to post.  He’d wants to emphasize that it’s an off-the-cuff response rather than a comprehensive reply, which of course I appreciate; but I think it’s worth posting:

OK, here are just a few examples from the thousands that are in the literature, off the top of my head:

Using positive selection to identify the pathogenic mechanisms of HIV in humans: PNAS 102:2832-2837 (one of many such studies that are now appearing and are using positive selection in pathogens to identify pathogenic mechanisms).

Using phylogenies and positive selection to predict which currently circulating strains of influenza are most likely to be closely related to future flu epidemics: Science 286: 1921-1925.

Using evolutionary analyses to track epidemics in human populations: many examples that have wider health implications, but our study of transmission in a forensic case was an interesting example with a specific legal application; PNAS 99:14292-14297.

Using evolutionary analyses to identify new disease outbreaks: new examples in every single issue of Emerging Infectious Diseases.

Using phylogenetic analyses to identify whether polio outbreaks are from native circulating viruses or from reverted, escaped vaccines (which tells health workers which vaccines to use in these areas to eradicate disease): see review in Bulletin of the World Health Organization, Vol. 82, No. 1.

Identifying changes in sodium channel genes that are under positive selection for TTX resistance, which has led to understanding the function of human diseases that are caused by the corresponding substitutions in human sodium channel genes: Mol. Biol. Evol. 25(6):1016–1024. (I included this one to show that all of the examples are not from virus work; this is the original evolutionary work from Manda Jost and Harold Zakon, with our collaboration, but there has been follow-up on the understanding of human diseases that are produced from these same mutations, now that they have been replicated by in vitro mutagenesis)

This just scratches the surface. I think there are now more papers that use evolutionary methods and analyses in the human health literature than all other areas of biology combined. I think it is crazy to not acknowledge the numerous and important human health applications of evolutionary theory and methods.


Well, this is good enough for me — I gladly retract my earlier opinion that evolutionary biology hasn’t been of much use in medicine.  Thanks, David.

NOTE:  In the comments to this post, one reader asks whether David’s examples aren’t just genetic, having nothing to do with evolution?  David has posted a response.

Who is the type specimen of Homo sapiens?

March 20, 2009 • 12:43 pm

by Greg Mayer

The answer is: Carl Linnaeus, the great Swedish naturalist. But there’s a story behind this bare fact.

One of the great problems facing natural history in the 18th century was the problem of diversity: the great variety of plants and animals from all over the world that began flooding into European museums as the result of voyages of exploration. Although it was not until Darwin’s idea of descent with modification that a fully satisfactory solution to the problem began to come within reach, Linnaeus made a signal contribution by establishing a nomenclature– a system of names– by which this diversity could be ordered, and with which it was possible to discuss the problem.  The principles of the system have undergone considerable development since then, but the 10th edition of Linnaeus’ Systema Naturae remains the starting point of zoological nomenclature.

One of the post-Linnaean developments is that all species should have a type specimen. A type specimen is not, as the name might seem to imply, a typical (in the sense of normal or average) member of a species.  Rather it is a specimen that fixes the application of a name to a particular zoological species.  Thus, I know that the name Anolis roosevelti applies to the large, arboreal (and now, unfortunately, apparently extinct) anole lizard of the islands east of Puerto Rico, because I can go the Museum of Comparative Zoology and examine the type specimen that is kept and carefully preserved there, and see that this specimen is indeed a member of that species.  Having the application of a name fixed is most important when it turns out that more than one species is masquerading under one name.  My friend and colleague Richard Thomas of the University of Puerto Rico, for example, discovered that Eleutherodactylus portoricensis, one of the most beloved frogs of Puerto Rico, actually consisted of two species, one of which had previously gone unrecognized.  The type specimen of E. portoricensis belonged to one of these two species, so it, of course, retained the name portoricensis; the newly recognized one was actually the more common and widespread of the two, and he gave it the name  Eleutherodactylus coqui, after its vernacular name, coqui, which was given in imitation of its nocturnally ubiquitous call.

All of this is by way of introduction to the issue at hand: who is the type specimen of Homo sapiens? In last week’s issue of Nature, Andrew Hendry of the Redpath Museum says

curiously, humans have never had a designated type specimen, despite attempts by American palaeontologist Edward Drinker Cope to have himself so designated

Is this so? No. In 1959, W.T. Stearn, in an article (Systematic Zoology 8:4-22) commemorating the 200th anniversary of the 10th edition of the Systema Naturae, wrote

Since for nomenclatorial purposes the specimen most carefully studied and recorded by the author is to be accepted as the type [specimen], clearly Linnaeus himself, who was much addicted to autobiography, must stand as the type of his Homo sapiens!

While there is a certain tongue-in-cheek quality to this, it satisfies the criteria of the Code of Zoological nomenclature, and thus Stearn has designated Linnaeus as the type specimen of Homo sapiens (Linnaeus, in naming Homo sapiens, had not designated a type specimen, which in his day was not customarily done).

So, as noted at the start, we do have a type specimen, Carl himself.  Did the great paleontologist Edward Drinker Cope ever try to have himself made the type specimen of Homo sapiens? Again, no.  Although Cope did leave his body for study, and there may be an oral tradition at the Academy of Natural Sciences that he wanted to be the type, there’s no written evidence he did. Earle Spamer, now of the American Philosophical Society, wrote a detailed article (Proceedings of the Academy of Natural Sciences of Philadelphia 149:109-114) exploring this claim. The written claim arises in a popular book by Louie Psihoyos and John Knoebber called Hunting Dinosaurs, with a foreword by famed paleontologist Bob Bakker. In the book, the authors relate how in about 1993 they borrowed Cope’s skull, and traveled around with it, showing it to paleontologists.  Bakker, according to the story, told them that man had no type specimen, and since Cope wanted to be it, they set about making it so.  But even if Bakker was unaware of Stearn’s designation decades earlier, the details of the story are all wrong.  Bakker would have known that a type designation does not require the description and measurements pictured and described in the book, that the type specimen must be chosen from among specimens examined by the original author (in this case Linnaeus in 1758, 82 years before Cope’s birth), and that there is no official “review board” to which such designations are submitted (the International Commission on Zoological Nomenclature can be appealed to in order to set aside the rules, but they don’t review actions that follow the rules).  In the foreword, Bakker himself makes no mention of ever having tried to actually make Cope the type specimen. No publication by Bakker claiming to make Cope the type has ever appeared, and Psihoyos and Knoebber’s journalistic account of Bakker’s supposed but unfulfilled intention to do so does not itself constitute a published nomenclatural act under the Code of Zoological Nomenclature.

It’s hard to tell how much Bakker might have been pulling Psihoyos’ and Knoebber’s legs, or just playing along, or if the authors just misinterpreted a lot of what Bakker said and did. Spamer seems to take this all a bit too seriously, and may err in ascribing much of it to Bakker, who did not actually author any part of the book but the foreword. But Carl Linnaeus is the type specimen of Homo sapiens; and Edward Drinker Cope has never been put forward for the job, and, without special action by the International Commission, he wouldn’t even qualify for it.

(Note by JAC:    Thanks to Dr. David Hillis of the University of Texas at Austin, who helped clarify this situation.)

Update: I’ve just come across a newspaper article that says that Bakker did publish a designation of Cope as the type specimen in 1994 in the Journal of the Wyoming Geological Society. The author of the newspaper article, Scott LaFee, did speak to some knowledgable people, including Ted Daeschler and Gary Rosenberg of the Academy of Natural Sciences. The article doesn’t note, though, that Cope is barred from being the type specimen because he wasn’t among the specimens seen by Linnaeus, and that Stearn’s designation (although mentioned by LaFee) preempts any later designation by Bakker. LaFee also seems to think a type specimen must be “typical” in the sense of average, which, as noted in the original post, it needn’t be.  I’m going to try to track down Bakker’s paper, and will post my findings here.

Update 2: I’d posted the update right after finding the mention of the article in the  Journal of the Wyoming Geological Society, because I thought it would take me a while to get a copy of the right issue of an obscure journal, and I wanted to immediately correct my claim that Bakker never published. Well, it turns out I was right in the first place. There is apparently no such journal.  There isn’t even a Wyoming Geological Society (there is a Wyoming Geological Association). I’m not sure where the claim originates: I’ve not found a mention of the fictional journal in Psihoyos’s book. It seems to me that some deliberate joking has gone on here. I’ll also mention here that I’ve seen some web commentary to the effect that Stearn’s designation doesn’t count, because “nobody can agree“.  This is incorrect: nomenclatural actions that follow the rules are valid, regardless of whether or not others think it was a good action to take.