The Myth of "Living Fossils"

The general public has been told time and time again that there exist among us certain species that have not evolved for millions of years. These so-called "living fossils" have somehow managed to avoid any changes in the frequencies of alleles in their evolving populations. This is, of course, impossible by any reasonable definition of evolution, a conclusion that was promoted on two decades ago [Claim CB930:].

Yet the myth persists. It persists for three reasons:
  1. It plays into the popular misconception that natural selection is synonymous with evolution. If a species isn't adapting by obvious changes over time then it isn't evolving. Another way of saying this is that some species can be so perfectly adapted to their environment that all changes are selected against and negative selection prevents evolution.
  2. External morphological changes are the only evidence of evolution.
  3. The so-called "living fossils" show no evidence of morphological change over millions of years when, in fact, all of the popular examples show plenty of evidence of such change. In other words, the facts are misrepresented.
The last time I blogged about this was just a few months ago when I commented on the first episode of a BBC television documentary called "Survivors." The main topic of the first episode was "Horseshoe crabs are one of nature’s great survivors" and the scientist behind the series is Richard Fortey, a paleontologists at the Natural History Museum in London (UK). I pointed out that some of his statements were misleading and I also explained why horseshoe crabs have evolved according to the scientific evidence [Evolution of Horseshoe crabs].

Why is this important? Because it's wrong to promote incorrect versions of evolutionary theory.

Today's New York Times Book Review has a review of a new book by Richard Fortey called "Horseshoe Crabs and Velvet Worms." The review [Some Things Should Be Dead] praises the writing style and readability of the book but, like most science journalism, does not get into details about the accuracy of the text.1

While preparing this post, I discovered that Jerry Coyne had also read the review [Two New Biology Books]. Coyne has met Fortey and thinks him a "lovable bear of a man, infectiously excited about biology." However, Coyne wonders what explanation Fortey will offer to support his claim of fossil species.
Fortey has a new book, and it’s about “living fossils,” those plants and animals that have persisted for millions of years without much change in their morphology (think ginkgo tree, coelocanth, and horseshoe crab). To evolutionists, these species are a mystery: why have they remained unchanged so long? One explanation—that they simply lack genetic variation that fuels evolution—is probably wrong: work ages ago by Bob Selander and Dick Lewontin showed that horseshoe crabs are just as genetically variable in their DNA as more malleable species. Another classic explanation is that these species simply live in unchanging environments, so that they arrived at their optimal morphology eons ago and there’s nothing new to adapt to. That’s an appealing but largely untestable explanation, especially because some creatures that live in similar habitats (like the shallow marine habitats of the horseshoe crab) have undergone substantial evolutionary change.

At any rate, Fortey’s new book is "Horseshoe Crabs and Velvet Worms: The Story of the Animals and Plants that Time has Left Behind," and it was reviewed in Thursday’s NYT. Reviewer Dwight Garner gives it two thumbs up, and I’ll be reading it for sure, if for no other reason to see Fortey’s explanation for unchanging species.
I'm not going to buy the book 'cause the only explanation I could accept would be that there's no such thing as a living fossil. I might be interested in a lengthy discussion about the different between natural selection and random genetic drift and/or a discussion about the kinds of morphological changes that have been observed recently among the four living species of horseshoe crabs but I doubt that would be in Fortey's book. Maybe Jerry Coyne will read it and prove me wrong.

1. This is a pet peeve of mine. The top three most important criteria of good science writing are: accuracy, accuracy, and accuracy. If a review doesn't tell me about the quality of science in a book then the review is completely useless. I don't care if the book wins a Pulitzer Prize (given out by non-scientists) for being an enjoyable read that sounds convincing to most readers. I don't judge science writing by style as the first criterion, nor do I judge it by the personality of the writer.
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