Intelligent Design

Species: What exactly IS a species?

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My friend Forrest Mims, one of the 50 best brains in science, according to Discover Magazine, writes to say,

Your post on “DNA analysis means death of taxonomy (determining what a “species” is)?”

This is a significant post that should be of interest to the ID community.

I have considerable experience with this, having studied for 7 years variants of the baldcypress found along Texas Hill Country streams and rivers. Let us go so far as to assume that all baldcypress are the same species: Taxodium distichum, including T. mucronatum, the national tree of Mexico. This leaves the problem of assigning scientific names to the variants of the species, including those I study that have a very different appearance from the common baldcypress. Even the annual growth rings and distribution of tannin in the rings is obviously different.

In a future book I’ll discuss some of my extensive correspondence with the new/old generations of botanists about my findings. The old generation is confident of the findings, but the young generation refuses to look at the actual specimens and wants only to see its DNA.

My main web site has a photo of the common baldcypress and the variants I study. Go here and scroll to end of page. The photo is low res on my site, but anyone can see the obvious difference that the molecular biologist I dealt with refused to acknowledge.

Speaking for myself, I have long been confused by the concept of “species” because it seems to be used in different ways.

Everybody agrees that beetles and butterflies belong to different species, but no one needs special training to see that.

But are dogs, wolves, and coyotes really different species? It’s no secret that they can interbreed. Most sources discourage interbreeding because wolves, coyotes, and their offspring are not desirable domestic companions compared to dogs.

Should behaviour count in relation to species?

Horses and donkeys can also interbreed, but the resulting mules and hinnies are not fertile. So with them we are developing a clearer idea of what a species is.

Some animals that are generally considered members of the same species – Chihuahuas and Newfoundland rescue dogs – may not be able to interbreed for logistic reasons (size difference). But before we go making a big “evolution” argument out of that, we need to stop and remember that those animals were bred by humans for specific tasks, and would probably not be viable in nature.

Maybe the best long run solution would be a figure for the type and amount of genetic difference that should prompt us to classify a given life form as a different species from another.

(Note: The Discover editors, to their credit, did not back down when challenged over their choice of Mims, due to his ID sympathies. Indeed, they were wise to stand their ground. If they dump “best brains” due to politically incorrect sympathies, they must replace them with “second best” brains, at least in their own honest opinion. In short, having the correct opinion becomes more important than adding to knowledge. That is a classic recipe for cultural stagnation that they did well to avoid. As I said at the time, “Science motors along on facts, so political correctness is not one of the branches of science.” )

Here is Forrest’s comment, published at Science (free registration wall):

The Twilight of Taxonomy
by Forrest Mims III

[Comment posted 2009-06-03 12:22:04]

Bob Grant’s piece on the fading of taxonomy (http://www.the-scientist.com/2009/06/1/32/1/) deserves a wide audience while there is still time to salvage what is left. The National Science Foundation should especially acknowledge this serious problem.

We have entered an era when some molecular biologists seem more interested in extracting DNA from museum specimens than in adding to the collections. A classic example is the destruction of very rare specimens preserved in amber to attempt DNA extraction (Mims, 1993).

For 7 years I have studied variants of the baldcypress found along Texas Hill Country streams and rivers. Let us go so far as to assume that all baldcypress are the same species: Taxodium distichum, including T. mucronatum, the national tree of Mexico. This leaves the problem of assigning scientific names to the variants of the species, including those I study that have a very different morphology than the common baldcypress. Even the annual growth rings and distribution of tannin in the rings is obviously different. While the old generation of botanists I have consulted is intrigued by these findings, the young generation has a very different view based solely on DNA.

Satellite remote sensing technology can lead to issues analogous to the twilight of taxonomy. For example, a decade ago colorful sunsets accompanied by extended twilights were observed from South Texas. These twilight glows looked much like those that followed the volcanic eruption of Mount Pinatubo and suggested a new aerosol layer in the stratosphere. After I posted these observations on the Internet, two experienced twilight observers were among the respondents who reported seeing the same phenomenon. I then sent an inquiry to a team charged with measuring optical depth from a remote sensing satellite. Their response was that the twilights were probably caused by smoke from Mexican power plants, an impossibility due to the stratospheric altitude suggested by the lengthy duration of the twilight s. I suggested to the team that they simply go outdoors to watch the twilights with their own eyes, but persistent sulfate smog over their location blocked their view.

In the end, the high-tech satellite completely missed the phenomenon. Observations by much older lidars in Cuba and California confirmed the new aerosol layer that was first discovered simply by measuring the duration of twilight glows using unaided eyes and a watch (Mims, et al., 1996).

Forrest M. Mims III
www.forrestmims.org
www.sunandsky.org
twitter.com/fmims

References:

F. M. Mims III, Save the Amber, Nature 362, 389 (1993).

Ibid., et al., Lidar data from Cuba, Germany, and Hawaii; aerosol layer with unknown source, Bulletin of the Global Volcanism Network (Atmospheric Effects), http://www.volcano.si.edu/reports/bulletin/contents.cfm?issue=atmospheric, (February 1996).

Also just up at The Post-Darwinist:

Podcasts and a reading from interesting blogs: Perfection in biology? And new podcasts

Quantum computing: US to axe work?

And don’t forget: Uncommon Descent Contest Question 5: Darwinian fairy tales: Why middle-aged men have shiny scalps

14 Replies to “Species: What exactly IS a species?

  1. 1
    Dave Wisker says:

    A good resource for speciation topics is a page maintained by geneticist Jim Mallet’s lab:

    http://www.ucl.ac.uk/taxome/jim/Sp/Sp.html

  2. 2
    Alan Fox says:

    @ Dave Wisker:

    I suspect your link is broken, Dr. Wisker.

  3. 3
  4. 4

    I’ve written fairly extensively on this very subject, including the following:

    http://evolutionlist.blogspot......cious.html

    Here’s what I wrote at the conclusion of that blog post:

    “Perhaps Darwin’s most important insight was his realization that species are not immutable, that they can intergrade over time in an “insensible series.” But what Darwin didn’t have the courage to come right out and say, and what most evolutionary biologists in general don’t have the courage to propose, is that there are really no such thing as species at all, at least not in the way we have traditionally defined them.

    Darwin should have realized this: he made it clear that natural selection happens at the level of individuals, never at the level of species. Evolutionary biologists have agreed with him, but have not taken the obvious next step: to declare that individuals living organisms are the only things that exist in the natural world, and that species (including animal species) may quite literally be figments of the human imagination.”

    Both evolutionary biologists and ID supporters seem obsessed with two related, but very distinct aspects of Darwin’s theory of evolution:

    • the origin of evolutionary adaptations, and

    • the origin of “species”.

    Darwin’s most famous book, the Origin of Species touches on both of these topics, but is mostly concerned with the former. This is not surprising, as Darwin originally published the Origin as an “abstract” of a much longer (i.e. multi-volume) work he had been writing for twenty years, entitled Natural Selection (it was eventually published, more than a century after his death, based on his voluminous notes and correspondence).

    One of the most interesting aspects of the EB vs ID controversy is that fact that many ID supporters (including Michael Behe) accept Darwin’s idea of “descent with modification”. That is, they accept his theory of the divergence of species into multiple descendent species. What they (and many of Darwin’s contemporaries and supporters, including Asa Gray, Charles Lyell, and even T. H. Huxley) do not accept is Darwin’s explanation for the origin of adaptations.

    To me, this is doubly ironic, as some contemporary evolutionary biologists have themselves questioned the whole idea of “adaptation”. I have written about this as well, at:

    http://evolutionlist.blogspot......-real.html

    The concept of “adaptation” itself includes an assumption of teleology. Adaptations are “for” some “function”, and can be described in sentences that use the phrase “in order to” without sounding nonsensical. For example, it doesn’t sound ridiculous to say that “mammals have fur in order to keep warm”, yet it does sound nonsensical to say that “dropped objects fall in order to reach the ground. The latter is a naturalistic description of the behavior of falling rocks, while the former is a teleological description of “function” of fur in mammals.

    I think it would be interesting for partisans on both both sides of these issues to consider for a moment what a theory of evolution (or, if you prefer a theory of “origins”) would look like in which neither “species” nor “adaptations” were the primary focus of attention. What would such a theory be like, what kinds of data would support it, and what implications would it have for science in general, and biology in particular?

  5. 5
    Dave Wisker says:

    Thanks, Alan. BTW, I’m not a Dr.

  6. 6
    Nakashima says:

    Mrs O’Leary,

    Maybe the best long run solution would be a figure for the type and amount of genetic difference that should prompt us to classify a given life form as a different species from another.

    It is an interesting suggestion, but that is exactly what Mr Mims was complaining about – the reduction of systematics to DNA analysis.

  7. 7
    Dave Wisker says:

    Hi Allen,

    But what Darwin didn’t have the courage to come right out and say, and what most evolutionary biologists in general don’t have the courage to propose, is that there are really no such thing as species at all, at least not in the way we have traditionally defined them.

    I like Dobzhansky’s comment that the species is not a static unit, but a stage in the process of evolutionary divergence. divergence.

  8. 8
    Alan Fox says:

    Thanks, Alan. BTW, I’m not a Dr.

    I am sure, judging by the erudition of your comments, it is only a formality. 🙂

  9. 9
    Alan Fox says:

    But what Darwin didn’t have the courage to come right out and say, and what most evolutionary biologists in general don’t have the courage to propose, is that there are really no such thing as species at all, at least not in the way we have traditionally defined them.

    I know Dawkins is not one of your favourite biologists, but he makes that point about there being no hard and fast division between species, especially temporally, several times in “The Ancestor’s Tale”, for example when discussing Homo ergaster and other “transitional” early humans.

  10. 10
    Alan Fox says:

    Sorry, that comment was directed at Allan MacNeill.

  11. 11
    Dave Wisker says:

    But what Darwin didn’t have the courage to come right out and say

    Well, he did say this in The Origin of Species:

    From these remarks it will be seen that I look at the term species, as one arbitrarily given for the sake of convenience to a set of individuals closely resembling each other, and that it does not essentially differ from the term variety, which is given to less distinct and more fluctuating forms. The term variety, again, in comparison with mere individual differences, is also applied arbitrarily, and for mere convenience sake.

  12. 12
    Joseph says:

    Allen MacNeill:

    Perhaps Darwin’s most important insight was his realization that species are not immutable, that they can intergrade over time in an “insensible series.”

    Linne figured out that spoecies are not immutable well before Darwin.

    As a matter of fact he once proposed that the Created Kinds were the existing species.

    He then changed that to the level of Genus- meaning that Creationists have accepted speciation since the time of Linneaus.

    IOW Darwin was fighting a strawman.

    Not that you guys will admit that but that is a fact.

  13. 13
    PaV says:

    Allen MacNeill wrote:

    Evolutionary biologists have agreed with him, but have not taken the obvious next step: to declare that individuals living organisms are the only things that exist in the natural world, and that species (including animal species) may quite literally be figments of the human imagination.

    There can be no doubt that the species question is one thorny mess. As I muse on this problem, I wonder if the way out of this mess is by not focusing on species, nor even on ‘individuals’, but instead on types of ‘cells’!

    You know the old cunundrum: What came first, the chicken, or the egg? Well, there is a definite answer: it is the egg.

    Consider organisms: they ‘develop’ from an egg=cell, and end in producing (reproducing) an egg=cell. Major differences in phyla and classes have to do with the difference in the type of eggs that are produced, if I’m not mistaken. Recent work suggests that cells can be reprogrammed by the actual molecular content of the cell, indicating a kind of ‘dialogue’, let us say, that the genome and cell share. Recent work also suggests that RNA’s and siRNA’s can be inherited (a la Lamarck) and have epigenetic effects. If, traditionally, taxonomists spoke of “kinds”, or “types”, then are the limits/demarcations implied by these terms the result of the ‘type’, or ‘kind’ of cells that exist. Certainly if evolution—and hence, reproduction—is involved, it is, roughly, (cell+1/2 genome) + (1/2 genome)=new cell; and maybe entirely too much attention has been paid to the genetic side of this equation. If reproduction is that which we feel defines ‘species’, then is the fundamental question needing to be asked is the following: what cells can be fertilized by what genetic material? Darwin thought of the cell as simple mass, while also minimizing any limits due to sterility. Maybe there are true limits. And maybe it is the cell that represents this limit. And maybe the way out of the woods on all of this is to study the natural divisions that occur among oocytes?

    Just musing here.

  14. 14
    Nakashima says:

    Mr PaV,

    It has been a long time since I read The Selfish Gene, but your reasoning sounds similar to his. He went further, past the cell to the gene as the important unit of consideration. My five yen!

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