Biology Evolution

The species problem in biology

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[From a colleague:] The species problem is real, but I think that (a) it is way overblown in importance in the phil. biol. literature as a result of our fixation on metazoans; and (b) it may already have a pretty good answer (Paterson’s “recognition” concept).

Briefly, on (b): the idea is just that the “glue” holding species together is the fact that members recognize each other as members, which is a fact about their cognitive systems analyzable in terms of pheromones or whatever. Of course, there is also the fact that recognition has to be correlated with reproductive viability, which raises all the usual design issues. But I don’t
see that there are any deep problems here that are not deep problems of biology, generally.

As for (a): The reason this problem is overblown is that (i) it is not universal (it really only arises in sexually reproducing species), and (ii) it is a subset of the deeper problems of biological unity or holism. The deeper problems are: How do the individual cells in a
multi-cellular organism achieve unity? and: How do the macromolecules within a single cell achieve unity?

If we knew the answers to these deeper questions, the species problem would answer itself. At any rate, by merely the posing the questions in this way, one can see that the species problem is a relatively superficial one. The fact that it has been so central to the analytical phil. biol. literature just goes to show how superficial that entire literature is.

14 Replies to “The species problem in biology

  1. 1
    John A. Davison says:

    There is no species problem. It was a Darwinian, Theodosius Dobzhansky, that presented a clear, testable criterion defining what species are. Two forms are considered to be separate species when either of the following criteria are met. They cannot produce a hybrid or the hybrid, when viable, proves to be sterile. It is perfectly unambiguous. The key word here is CANNOT produce a hybrid which requires artificial insemination to be fully significant.

    Josef Goebbels, Hitler’s Propaganda Minister, took advantage of Dobzhansky’s definition when he proclaimed, and I must paraphrase as I do not have the original handy:

    “It has not yet been demonstrated that non-Aryans cannot hybridize with apes.”

    Apparently the Nazis had performed such experiments. Personally I see no compelling reason why a human/chimpanzee hybrid might not be viable but, with at least a dozen different chromosome restructurings separating the karyotype of the chimp from that of the human, the hybrid most certainly would be sterile.

    A primary factor in speciation has been chromosome restructuring as synapsis between structural chromosome heterozygotes invariably leads to some sterility because crossing over in the nonhomologous regions leads to the production of unbalanced, non functional gametes. This is true even if the chromosomes are identical at the allelic level and has a purely mechanical basis. We are practically identical with our primate relatives at the allelic (Mendelian) level anyway. It was the chromosome and not the gene that was always the mediator of evolutionary progress just as Goldschmidt claimed sixty-six years ago.

    “Species and the higher categories originate in single macroevolutionary steps as competely new genetic systems. The genetical process which is involved consists of a repatterning of the chromosomes which results in a new genetic system.”
    “The Material Basis of Evolution, page 396.

    If only he had used the past tense!

    There is also no reason why such experiments should not be performed and the results reported in the professional literature. Perhaps they have been. I don’t know for sure. Does anyone?

    “A past evoution is undeniable, a present evolution undemonstrable.”
    John A. Davison

  2. 2
    scordova says:

    The large-scale differences of form between types of organism that are the foundation of biological classification systems seem to require another principle than natural selection operating on small variations….

    Organisms are as real, as fundamental, and as irreducible as the molecules out of which they are made…

    The recogonition of the fundamental nature of organisms, connecting directly with our own natures as irreducible beings, has significant consequences regarding our attitude to the
    living realm….

    …one of Darwin’s most cogent critics was St. George jackson Mivart, who marshalled an impressive array of evidence that adaptation to the environment by natural selection is a quite inadequate basis for explaining species morphologies.

    Brian Goodwin, 1994
    How the Leopard Changed it’s spots

    Goodwin argues there are organizatonal laws which define the architectures which species can fill, and which architectures are ruled out. Thus the classification of species might work out just like the periodic table. It is governed by some sort of organizational law.

    It is reminiscent of Mendeleyev who could tell a certain element should occupy a position on the periodic table of elements even before the element was discovered. It seems D’Abrera and Sternberg have been seeing similar developments in their fields of biology with respect to missing species. Some sort of organizational law is in effect, and even creatures never seen can be predicted to exist. Unfortunately, I only learned of D’Abrera and Sternberg’s work second hand form Mark Ryland, and have tried in vain to discover what they actually did in the way of a periodic table of species.

    Sal

  3. 3
    Joseph says:

    Two forms are considered to be separate species when either of the following criteria are met. They cannot produce a hybrid or the hybrid, when viable, proves to be sterile. It is perfectly unambiguous. The key word here is CANNOT produce a hybrid which requires artificial insemination to be fully significant.

    OK wait. So this guy knocks up this chick and their baby is sterile, are the guy and the chick a different species? What about homosexual couples? Are they a different species (being the couples cannot successfully mate with each other)?

    Successful mating could be part of a list that defines a species, but a small part.

  4. 4
    Alan Fox says:

    “It was the chromosome and not the gene that was always the mediator of evolutionary progress just as Goldschmidt claimed sixty-six years ago.”

    But a gene is any arbitrary length of DNA sequence from a codon to a chromosome that has alleles. As commonly understood, there is no qualitative difference between “gene” and “chromosome” other than the number of nucleotides in the sequence.

  5. 5
    John A. Davison says:

    Joseph

    If Homo sapiens suffered from a serious sterility problem there would not be nearly seven billion of us cluttering up the landscape. Sterility of certain couples is rapidly removed from consideration in a natural scenario. It is part of the one thing that natural selection can do which is to maintain the standard, in this case, intra-specific fertility.

    “A past evolution is undeniable, a present evolution undemonstrable.”
    John A. Davison

  6. 6
    Joseph says:

    JD:
    If Homo sapiens suffered from a serious sterility problem there would not be nearly seven billion of us cluttering up the landscape.

    That is not what I am saying nor implying.

    Say the girl in my scenario could not successfully mate with any man on Earth save one. And that one man could not successfully mate with any other woman except for the original girl in my scenario. Would that or would that not make those two people a different species under the definition given in comment #1?

    JD:
    Sterility of certain couples is rapidly removed from consideration in a natural scenario.

    Obviously but that misses my point. The sterilty of you hybrid would meet the same fate. I am just going by the definition YOU provided.

    JD:
    It is part of the one thing that natural selection can do which is to maintain the standard, in this case, intra-specific fertility.

    Irrelevant. My scenario meets the criteria of the definition- period.

  7. 7
    Charlie says:

    What is the relevant point of your scenario, Joseph?

  8. 8
    John A. Davison says:

    Apparently Alan Fox thinks a chromosome is little more than a string of genes. Get with the program Alan. Nobody believes that any more except you maybe. If we were identical at the DNA level with our closest relative the chimpanzee, we would still be chimp and human respectively. We are practically identical at the gene level anyway. There is not a shred of evidence that allelic mutation played any role in any evolutionary event except possibly to ensure extinction as deleterious mutations accumulated. Thank the Lord for extinction, Without it there could never have been evolution. That is about all that Mendelian mutations were ever good for. Get used to it. Pierre Grasse did and so have I. Only Darwinian mystics still adhere to a Mendelian evolution. Sexual reproduction WAS impotent as a creative device and so WAS population genetics. Natural selection WAS and still IS also entirely anti-evoloutionary. That is why every chicadee looks like every other chickadee. They even all sound alike!

    Chickadee – dee – dee, chickadee – dee- dee

    How do you like them apples?

    “A past evolution is undeniable, a present evolution undemonstrable.”
    John A. Davison

  9. 9
    John A. Davison says:

    Incidentally, Alan Fox follows me around like a “fox” from forum to forum wherever I happen to appear. As near as I can tell his sole purpose is to discredit whatever I say. He became so rabid that they banned him at “brainstorms.” He is a sort of one man “goon squad” for Wesley Elsberry at whose forum by fiat my name is never to be mentioned again. Alan has freely admitted that he is afraid to mention my name at Panda’s Pathetic Pollex for fear of lifetime bannishment. Isn’t that precious? The Darwinians have always pretended that they had no critics, but we bloggers know better don’t we.

    Naturally –

    I love it so!

    “A past evolution is undeniable, a present evolution undemonstrable.”

  10. 10
    Joseph says:

    Charlie:
    What is the relevant point of your scenario, Joseph?

    My point is less ambiguous than the definition of species. Are the two people a new species or not? According to the definition in comment #1 they must be.

  11. 11
    John A. Davison says:

    Take it up with Dobzhansky joseph. It was his definition, not mine.

    “A past evolution is undeniable, a present evolution undemonstrable.”
    John A. Davison

  12. 12
    Charlie says:

    Joseph,
    I have been enjoying your own blog for a while and know that you have an opinion on biology and its ability to tell us what a species is.
    As far as I can tell I share that opinion and I think we both agree with the last paragraph of the OP here:

    If we knew the answers to these deeper questions, the species problem would answer itself. At any rate, by merely the posing the questions in this way, one can see that the species problem is a relatively superficial one. The fact that it has been so central to the analytical phil. biol. literature just goes to show how superficial that entire literature is.

    I was hoping that by asking you what your point was you could flesh this idea out, for my benefit, and for the other readers.

  13. 13
    Joseph says:

    JD:
    Take it up with Dobzhansky joseph. It was his definition, not mine.

    John- that is why in comment #10 I said the definition in comment #1 and NOT John Davison’s definition of species. Perhaps you posted the definition being sarcastic and that went right by me without my noticing.

    Charlie-

    I agree with the OP. I was disagreeing with TD’s definition as provided in comment #1.

    But anyway, as I have stated reproduction could be part of the formula for making a determination about differing species. I just wouldn’t make that a main or driving part of the equation. I say that because if divergence can (allegedly) eventually cause lack of reproductive success then convergence could allow for reproductive success in organisms whose alleged common ancester died out illions of generations ago. It (reproduction success) also doesn’t work on asexually reproducing organisms or fossils.

    The whole “species” thing is just our way of trying to catagorize things in nice neat lists. We do this as if we are the final authority on the subject. So my first questions would be “Why are we catagorizing populations? What are we trying to accomplish?”

    I understand what Linneaus was trying to accomplish. He was searching for the originally Created Kinds. But I do not recall his methodology.

    Patterson’s recognition (b) in the OP seems “real” with some exceptions-> dogs and humans legs come to mind 😉 -> some humans and whatever they can get their hands on also comes to mind. So is it a drive to reproduce or a drive for (sexual)satisfaction? But perhaps he is on to something as in the “birds of a feather, flock together” scenario. But if we use that then different human races would be a different species IF the different races those races stayed separated.

    I guess the bottom line is any such “tests” appear arbitrary. It may be that some scientist’s kid(s) were always bugging him/ her about “what is that?” and thus began our little journey to put life in a neat top-down form and give each observed organism a common and scientific name- just so adults could answer their kids with something that to the kids sounds OK.

    That said, my take has always been that once we know what makes an organism what it is, and only then, will we be able to make sense out of our feeble attempts to put life in neat lists.

  14. 14
    John A. Davison says:

    Speaking of ontogeny and phylogeny:

    “Neither in the one nor in the other is there room for chance,”
    Leo Berg, Nomogenesis, page 134.

    I only wish he had used the past tense for phylogeny as it simply is no longer going on. Got that? Write that down.

    “A past evolution is undeniable, a present evolution undemonstrable.”
    John A. Davison

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