Endless forms most continuous

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What is evolution? I just had someone email me that people often ask him about his “belief” in evolution. This reiterates the point that people consider evolution a belief system, not a scientific paradigm. No matter how ridiculous it seems, how is it that we arrived at this juncture? There are multiple factors that have resulted in ~1/2 of Americans rejecting any form of evolution.

One important point is the reality that human beings as essentialists. That is, we imbue animals with essences. Elephants are elephants, even if you dress it up like a giant flamingo, there is something essential about elephants that is preserved. Paul Bloom would root this in our innate dualism. Others would elaborate in more detail aspects of innate derived folk biology. Children from Creationist and non-Creationist backgrounds tend to prefer narratives which imply immutable and essential natures to creatures all around them. As a point of plain fact that is what we see with our naked eyes. Whether or not evolution has shaped us toward a particular bias in regards to systemetizing about the natural world, the inputs we receive from the environment early on in development reinforce our conception of an ordered and discrete world where the essence of elephant is poured into the flesh of the proto-elephant.

This sort of thinking crops up in folk systematics (in mythologies about the beasts and birds and fish of the sea) as well as Creationist tracts which emphasize the importance of “kinds.” Obviously Creationists have problems with hybrids like mules, and in particular, fertile hybrids like female tigons. But it is not only Creationists who have problems with female tigons, biologists who espouse the biological species concept (BSC) also have issues with the reality of fertile hybrides (this is why the peculiar, at least intuitionally, phylogenetic species concept emerged [PSC]).

The BSC was promoted by the famous evolutionary biologist Ernst Mayr. Mayr also was a thinker in an older school of evolutionary phylogenetics which relied on the intuition and knowledge of specialists in particular clusters of species. The problem is that the BSC, that a species is defined by the bounds of fertile matings across a population generating fertile offspring is not workable across vast swaths of the tree of life. Not only do asexual creatures fall outside of the testable criterion of viable crosses between two individuals (unless you count various forms of horizontal gene transfer), but many traditional species generate fertile hybrids, and amongst many plants hybrid viability is so omnipresent as to make a joke of the BSC. The problems with the BSC and evolutionary phylogenetics resulted in the rise of the cladists in the 1960s, who emphasize the use of synapomorphies in determining monophyletic clades. A mouthful, huh? Cladists and the simultaneous rise of phylogenetic trees were welcome revolutions in turning systematics toward a more deductive and falsifiable set of methods. But the problem is that the hypothetico-deducative methods that lay at the root of these new fields are not necessarily intuitive. That makes sense, as I have said multiple times, human operational thought is not deductive, but abductive, we work from a set of facts to a good working explanation, we do not work from a hypothesis to predictions which we rigorously test.

There are rough & ready concordances between the intuitive phylogenies that were produced by Mayr’s school, and even Haeckel’s Tree of Life. For that matter, conventional human creation stories generate decent evolutionary relationships as well, they are clearly not random fabulations, but derive from a solid grounding in the data on hand. The problem is that science is a precise and reproducible system, and gestalt knowledge can usually only be resolved by appeals to authority and loud shouts of “You’re wrong, because I said so!” Despite the excessive fanaticism of cladists on shared derived characters, the rigor that they brought to systematics was certainly a good thing. And the challenge that they put forth to the BSC was also a good thing.

Because species are problems. Aside from species it is a traditional point of understanding that other taxonomical categories are arbitrary, i.e., genus (note that humans are not in the same genus as chimpanzees, though this does not make taxonomical sense). But even species can be problematic. This is an issue because the intuitions that we as humans have about species are, in my opinion, a major grounding for Creationist rejection of evolutionary theory. Once we dethrone species, intuition will no longer be the block it currently is. No longer will we have to appeal to the Talk Origins observed speciations page. No longer will we have to respond to the charge that there have been no observations of radical changes in body plan in one generation. No charges that “bacteria don’t evolve.” Ultimately these battles can be won, but the greater war is the sanctity of species, “kinds.”

Plant geneticists like Loren Rieseberg of the University of Indiana have been studying the importance of hybridization amongst various “species” for many years. Not only does a retrofit of Biblical systematics stumble upon the ubiquity asexual microorganisms, it is a poor representation of evolutionary genetic dynamics amongst the primary producers of biogenic matter on this planet, the plants. Unlike animals various plant species hybridize promiscuously, and one could say that for some taxa the term species is simply shorthand for correlation structure across space and time, interlaced by a continuity of gene flow.

But how relevant is this for animals? Clearly animals do not hybridize as easily as oak trees or sunflowers. Nevertheless, essentialist truths collapse with the insertion of slim needles. Species concepts are build upon a house of cards which assumes that populations which are so demarcated are (magically) insulated from affinal populations by mating barriers, whether it be prezygotic (behavior, mating season, etc.) or postzygotic (lower fitness of hybrids, hybrid sterility, etc.). But the intuitional concepts are grounded (more or less) in an absolutist model, not a graduated one. Like fucks like.

In How species evolve collectively: implications of gene flow and selection for the spread of advantageous alleles Rieseberg and Moran explore the importance of interpopulational gene flow in maintaining a rough species cohesion. Their contention is that advantagenous alleles of large effect can spread through a worldwide population via selection even when migration is not sufficient to homogenize neutral alleles. In short, Reiseberg and Moran save the species concept by suborning the impression that a species’ genetic architecture is a unitary and hypercontingent black-box which can not brook change or introgression. As I have noted before, the effect of gene flow on the distribution of frequencies across and within populations can be modeled with the equation 1/(4Nm + 1), where N is the population and m the proportion of migrants per generation. In short, Rieseberg and Moran argue that the rate of migration between populations within species is simply too low for genetic drift and local adaptation not to result in speciation. On the other hand, they argue that genes of large fitness effect may be able to spread even when the migration rates are not sufficient to equilibrate most of the genome. Recall that the probability of a mutation of fixation is 2s, and this can be translated into models which use migration in lieu of mutation to introduce genetic novelty. When s, the selection coefficient that defines the fitness of individuals with the allele vs. population mean fitness, is low, the probability of fixation is low, and random genetic drift is very powerful. But as s gets larger the probability of fixation increases and random genetic drift has a proportionately weaker role in the dynamics of frequency change. Rieseberg and Moran suggest that even on quantitative traits, where there are many loci, the locus of largest effect often explains a large fraction of variation, in which case the the alleles at these loci that confer great fitness will be able to sweep over worldwide populations and maintain species cohesion.

But the lessons to be learned from this paper extend beyond maintenance of putative species, they suggest the pluralism of microevolutionary mechanisms which are at work on the populational level. But we can take this further, in his paper The scale independence of evolution Armand Leroi expresses skepticism at the tendency for some to assert radically different dynamics on the macroevolutionary vs. microevolutionary level (i.e., clade level selection, etc.). He argues that there is a continuity between the two levels, microevolutionary forces of selection and drift are sufficient to explain taxonomical variety and novelty. This is an important point because it speaks to the idea that species and genus’ are not privileged, and despite their operational intuitional appeal we may need to move beyond innate systematics to understand how evolution actually works as a process. Rieseberg above argued that spread of alleles of large positive selective effect tie together species, but other work by plant geneticists shows that such alleles can spread across “species.” The essentialist concept of species is a fundamental block in the road to being open to this possibility. If species have peculiar essences sealed off from others it makes little sense that traits of one species would spread to another.

We privilege individuals and species as operational units because they are highly salient. Our minds are geared toward recognizing moving objects as individuals with agency. Faces are not simply smudges against the background, they stand out with particular detail. But in the broad scope of evolution individuals, and species, might not be as special as we believe. Certainly species are not intelligible in the context of asexual creatures beyond a gestalt level, and it is a highly problematic concept in plants as well. In concert with our tendency to think in terms of expanding non-reticulated genealogies, the species concept might be blocking our ability to understand the evolution of our own species. On the comment boards of this weblog someone expressed the idea that modern humans would simply not mate with neandertals because of physical differences. But the reality is that we know that humans have sex with ungulates. I believe what is happening is that we are abducing to the best possible explanation of the reality that we know we are special, and different. In their book Speciation H. Allen Orr and Jerry Coyne scoff at the possibility of human & non-human primate hybridization. This shows that even biologists are not immune from this bias when it comes to our own species. Orr’s work in particular has shown that mutations which generate fitness benefits of large effect can spread rather fast, and operate outside the conventional infinte alleles models (which assume fitness differences of very small effect). Rieseberg uses Orr’s work above as theoretical underpinnings for the paradigm that he is pushing forward.

In The Selfish Gene Richard Dawkins promoted a “gene centered” worldview that deemphasized individuals as “vehicles.” This was in the context of microevolutionary theories promoted by W.D. Hamilton which derived the evolution of altruism from the realities of kinship and gene identity. But just as genes brook no differences of individuals, that is, we are simply vehicles that they use to traverse space and perpetuate themselves through time, so species may also be simply more difficult valleys to cross. Though sexual reproduction in our species is banal, when viewed across the span of eons, one can not ignore the possibility that interspecies matings could also be a process which is highly relevant to the evolution as selectively favored alleles that introgress might spread like wildfire. Genes are discrete units of information on the nucleotide level, but from their vantage point the existence of creatures of flesh and cellulose might simply be continuous scaffolds which present non-trivial, but not insurmountable, barriers to traversion. So, in answer to questions relating to speciation, I’m not sure how ground shaking these points really are in the grand scope of evolutionary theory.


  1. How might one estimate the fraction of the problem that should be ascribed to loss of faith in scientists? Alas, my own guess is that that loss is, in part, justified. 
    Only in part, of course.

  2. How might one estimate the fraction of the problem that should be ascribed to loss of faith in scientists? 
    zero. the % who have or haven’t believed in creationism has been stable in the USA for several generations. see ronald numbers the creationists. so if the ‘faith in scientists’ was relevant, than they didn’t have it in the first place. in any case, do you think the british have more faith in scientists? i doubt it (i.e., GMO hysteria). but they believe in evolution.

  3. Essentialism goes waaaaay back to Plato and his ridiculous forms. It has been inbuilt into the Western imagination ever since. Add to that Aristotle’s pernickety insistence on discrete,clearly defined categories and it is well-nigh impossible to imagine speciation as anything but the emergence of an autonomous, fully distinct entity from the loins of another. Compounding the confusion is the Biblical insistence that the world is 6000 years old, so there is no space for time to do its thing. No wonder no one believes in evolution.

  4. pismire, i think you have it backwards. essentialism is not popular because of platonism, platonism is popular because of essentialism. as for ‘no one’ believing in evolution, to some extent americans are a minority in the west in their rejection of the validity of evolutionary theory. but, i don’t think that fundamentally most people understand the theory of evolution, just as most people don’t understand newtonian mechanics beyond a few mantras about the 3 laws. the difference is that while there is no one arguing for aristotelian physics (which to some extent is out intuitive folk physics!), there are people arguing for an elaboration for intuitive folk biology and psychology (i.e., complex organisms must be the end products of design/agency). 
    p.s. in the early 20th century the new york times ridiculed goddard because obviously spaceflight couldn’t occur because thrust had nothing to ‘push against’ (i.e., in the vacuum/ether). this is 200+ years after newton’s 3rd law.

  5. Eat a man?s brain and heart and gain his intelligence and courage. Give me the muscles of the tiger and the agility of the monkey. Spread those genes.  
    Down with species! What do we want! Horizontal gene transfer. When do we want it! Now.

  6. Nice post, a bit too long. Even so, I cannot visualize a world of free horizontal gene flow, like bacteria. Even bacteria maintain a basic identity and can be classified in solidly defined species. Free “sex” (gene exchange) does not dissolve identities. Maybe I am wrong.

  7. Razib, “the % who have or haven’t believed in creationism has been stable in the USA for several generations”: pretty conclusive, that. 
    “do you think the british have more faith in scientists? i doubt it (i.e., GMO hysteria) but they believe in evolution”. I don’t know the answer to your question, but I do sympathise just a little with my countrymen in their GMO hysteria – when I heard a Government Scientist on TV assuring us that GM genes couldn’t spread to other plant species because those species would be protected from the spread of pollen by a zone several metres wide of bare, ploughed earth, I had a tremendous temptation to fling heavy objects at the telly and scream abuse.

  8. bio, there are serious issues with GMO, i don’t deny it. but hysteria is still that (though people are free to discriminate based on what seem to be ‘irrational,’ we don’t make vegetarians eat moderate amounts of meat or muslims moderate amounts of alcohol because they are healthful).

  9. Razib, what I’m driving at is that I hate it when a proposition is supported with purportedly “scientific” arguments that are, essentially, lies. The proposition that pollen blows down the wind for distances less than a few metres is one such. Similarily, the British hysteria about MMR injections seemed quite silly to me until I saw our Prime Minister evading questions and then telling lies about MMR and his own youngest child on TV. No wonder the layman starts to doubt much that he’s told. But rather far from your evolution point, I know.

  10. Razib,where is the post that discusses the gene flow equation? I can’t find it and can’t figure out what the equation means without an explanation.

  11. Come on, the reason people don’t believe in evolution is Christianity, and you know it.

  12. robert, here.

  13. “This is an issue because the intuitions that we as humans have about species is, in my opinion, a major grounding for Creationist rejection of evolutionary theory. Once we dethrone species, intuition will no longer be the block it currently is.” 
    Thank you, Razib. This was a major “scales falling from my eyes” moment for me. In my interactions with creationists I’ve come to the realization that you’re more likely to get somewhere constructive with them if you start from the bottom (molecular level) and work your way up; nobody finds chemistry objectionable, and if you can show that the rest of evolution follows logically from there in conjunction with some other equally unobjectionable facts, you can circumvent their antiprocess tripwires by avoiding any reference to species and whatnot alltogether. But I never made the connection as to why this method worked better until now.

  14. re: bacterial speciation, see the synopsis of a forthcoming symposium on the topic for what i’m talking about in terms of the relative muddle.

  15. I’m inclined to agree with scifigeek. 
    The reason Americans have problems with evolution is because of Biblical literalism, itself a consequence of a particular variety of Christian Protestantism.  
    Europe with its Catholic/Liberal-Protestant forms of Christianity is simply no longer drawn in that direction. In so far as Europe is Christian at all any more. 
    This doesn’t mean that Europeans are any more rational than Americans, by the way. If they don’t believe in Creationism so much, they make up for it by believing in Astrology and Atlantis and the Da Vinci Code and  
    Spiritualism and Tarot Cards and alternative medicine and …. 
    The truth is that rationalism is an elite ideology. There is no civilization anywhere, where more than a tiny minority believe in it – or at any rate believe in it exclusively. A lot of people believe in rationality as an “offical” form of magic. In a world where magic rules every aspect of their lives. 
    The intellectual life of the average citizen is far more primitive than you could possibly imagine. The majority of people have yet to catch up with the neolithic revolution, much less the scientific revolution.

  16. While there’s little doubt the phenomenon exists to some degree, I doubt this hyper-discreet sense of speciation plays as prominent a role as is being assumed. Much more prominent are the over-leveragings and presumptions by people like Dawkins – or scifigeek’s rank dismissiveness above. And are we to assume the other 50% of Americans (i.e., the good 50%, wearing the white hats) are any more intelligent or any less feckless, as a class, in forming their opinions? I’m not so sure as I’ve observed a lot of nonsense and blind faith rather than intelligible and well articulated opinions being formed and explicated from “that side of the aisle”. I happen to be both a theist (mea maxima culpa, a Christian theist at that) and an evolutionist, though I resist being labeled an “evolutionary theist” in the sense which political organizations like Eugenie Scott’s NCSE use the term (seemingly or virtually denoting a deistic, philosophical materialism, not merely a methodological materialism). 
    The entire discussion of non-discrete events, causations, processes, etc. is an interesting discussion, even outside of evolutionary biology. But I doubt it’s the basic or primary barrier, in and of itself, your post assumes. In fact there’s something of an irony here, imo, because that very conceptualization is itself a type of discreet (even if not intending to be simply monolithic) representation of that class. I strongly suspect it’s a great deal more involved, though again, am not disputing you can find the phenomenon, am only doubting it plays such a pivotal role.

  17. michael, we need to elaborate necessary and sufficient conditions. i am not saying that an intuitive understanding of essential species is the necessary and sufficient condition. i do not think that the perception that evolutionary theory is anti-religious is more or less important in generating anti-evolutionism in the public than folk biology, i am saying they both play a role. also, one might note that some biologists, like the late sj gould, go to great lengths to mitigate the atheistic implications of evolutionary theory, nevertheless, anti-evolutionary propogandists make sure and select quotations from people like dawkins to “prove” that evolutionary theory is anti-theistic in its fundaments. it seems to me that the only way that evolutionary theory and atheism can be decoupled is to make sure all evolutionary theorists are theists, because those opposed to evolutionary theory will selection bias toward anti-religious evolutionists. in other words, i don’t personally think that the anti-religious perception of evolutionary theory is as important as sometimes thought, because i think that people are naturally biased against evolutionary theory and will confirm their bias by its association with another movement which are they are ill-disposed towward (i.e., philosophical materialism and atheism, or eugenics, etc.). 
    And are we to assume the other 50% of Americans (i.e., the good 50%, wearing the white hats) are any more intelligent or any less feckless 
    yes, more intelligent re: standardized tests. several decades of gallup polls show a positive correlation between education and acceptance of evolutionary theory. but, not necessarily less feckless, it is more likely simply acceptance of elite cultural norms. there is some evidence that individuals who are more intelligent are more ‘rational’ in the sense of disregarding intuition and following their chain of reason (i.e., they are ‘rational actors’), but i suspect that is a minimal factor. 
    also, you are wrong about scott from what i know. perhaps you should examine your own perceptions? see here for a dialogue between scott and will provine, where scott defends methodological naturalism and seems to lean toward gould’s two magesteria (the term is usually “theistic evolutionist,” evolutionary theist would seem to imply sometime totally different, perhaps more in line with teilhard de charden ideas).

  18. Broncs/Bills halftime. Yes, i understand the difference between necessary and sufficient and did not impute a ‘sufficient’ quality to your argument. Keep in mind i said i don’t doubt the phenomenon, only doubt the degree of emphasis you’re placing upon it. We disagree. 
    Re, ‘more intelligent’ vis-a-vis standardized tests and gallup polls, I’d be interested in the specifics, the data, and the questions asked, etc., analysis of the polls, etc. It amy be true, but specific empirical data and examination of the polling questions would be pretty basic. 
    Re, Eugenie Scott and NCSE. I’m well aware of the debate with Provine, have read it in the past. Am also aware NCSE is a political org and Eugenie Scott is necessarily forced to take a pragmatic rather than more stridently ideological approach, to an appreciable degree, needing as she does to debate in the public square, in public forums, she is more limited here than a Provine, Dennett, Searle, Dawkins, et al. typically are. Am also aware of NCSE and Scott using “virtual slanders,” for example material in some of their presentations denoting literal “flat earthers” representing the first rung in the continuum of creationist/ID proponents. And since you’re using terms like propaganda, fittingly see, here, for an historican’s analysis of this subject now representing a well worn, century-old slander. 
    But also, beyond these types of virtual slanders and ridicules, also using literal slanders, for example in collusion with some numbers of people affiliated with the Smithsonian in their attack against Richard Sternberg. See here for a detail of Sternberg’s role and here for the U.S. Office of Special Counsel’s investigative findings of same. So, no, it’s not simply my perceptions, re Eugenie Scott and NCSE. Wish it were so. 
    As for minimizing the role which philosophical materialism plays in peoples perceptions vs. the sheer reality, Searle certainly comes immediately to mind again, Provine, Dawkins. Given enough time I can pull together, I’m quite confident, a review encompassing several thousands words with plenty of citations, but for now will simply not that, again, we disagree, and profoundly so.

  19. A year or two ago, I went to a dinner party, where one of the guests told us that they were wearing a magnetic bracelet to protect them against their various aches and pains. Another affirmed that he hadn’t tried magnetic bracelets, but that his mattress had magnets in it for the same “reason”. So it went. I’d guess fully half of the group had some kind of magnetic device in their lives to fend off the evil electromagnetism. So I thought to myself, “Aha, magnetism is the superstition du jour. One of the group is possibly influencing the rest”. 
    I sat there and listened to all this. Anthropoligist Dan among the primitive stone-age tribe.  
    I remember the young lady I met at one dance, many years ago. She was into crystals. Her face lit up when I told her that I too carried crystals with me everywhere I went.  
    Unfortunately I spoiled the effect by tapping on my watch and saying, “Quartz crystal watch.” 
    Bad mistake. Always get laid first, then criticise. 
    I find a lot of my acquaintances don’t even tell me any more about their latest fads. They know I’ll pooh pooh everything. I am “closed minded” it seems. I only find out about it when I am in a group and I keep quiet. Then I can see what they really believe, and the answer is “Anything”. Without the discipline of reason they are prey to every whim, every passing breeze. 
    Creationism is just the tip of the immense iceberg.

  20. BTW, even some biblical literalists believe in “microevolution”. God created different “kinds”, which don’t exactly correspond to species. Cattle is a “kind”, so there’s a common ancestor of domestica cattle and water buffalo, but not one between say cats and dogs. 
    Humna beings are special, of course.

  21. athiests unite  
    let us form our own new specie

  22. I’d be interested in the specifics, the data, and the questions asked, etc., analysis of the polls, etc 
    well, go to google. these numbers are reiterated in the press vi and in gallup & pew analyses every 6 months. you will see from the numbers that the % rejecting evolution has been rather stable for several decades, even predating the dennett-dawkins-scott cabal :) 
    I’m quite confident, a review encompassing several thousands words with plenty of citations 
    of course, that doesn’t speak to the representative accuracy of your argument, the sample space of citations can must run into the millions. surely you could find hundreds or thousands that could fit into a essay or book?

  23. You’re cautious and distancing in accepting a reasoned, empirically based, cited argument; yet incautious with dismissiveness and a scoff. Telling, that.

  24. You’re cautious and distancing in accepting a reasoned, empirically based, cited argument; yet incautious with dismissiveness and a scoff. Telling, that. 
    you are a muddled sophist. no more to say than that. and you shouldn’t speak of empiricism if you aren’t even familiar with the voluminous literature on american attitudes toward evolution-creation.

  25. You’re one to speak of muddledness and sophistry, not to mention pretensiousness and a self-authorizing quality. I’ll show myself the door since I’m wasting my time; I was originally hoping to find something more substantial here, more transparent, empirical and well reasoned. Also, you’re wrong, the reference as regards the empirical was to the campaigns of slander which Eugenie Scott’s NCSE had waged or helped to wage. It was that empirical evidence, cited, which you elided or dismissed – regarding Richard Sternberg’s case, here and here, and regarding the propaganda theme which you broached, here
    Thanks too for telling me I can use google. (Similarly, I could have suggested you google and better educate yourself concerning Eugenie Scott and the NCSE.) The point being however, if you have specific data then you can cite it yourself, you’re the one who brought up that topic in the first place. If you don’t care to forward it any further, fine. But I’m well aware of google. 
    Sophistry or more simply a self-authorizing dismissiveness, you excel. My first two posts here were aptly on-topic, you’re the one who resorted to the dismissiveness, the scoff, along with the elision or disregard of the evidence presented. Apparently I was suppose to have been impressed.

  26. “The intellectual life of the average citizen is far more primitive than you could possibly imagine. The majority of people have yet to catch up with the neolithic revolution, much less the scientific revolution.” 
    I think you would have to include a very large portion of the intellectual elite here too. I find that even among evolution believers, even a rudimentary understanding of evolution is sadly lacking, ” belief in evolution is more often than not a matter of ” faith” in the ideas and attitudes of the social class to which even the elites belong to.

  27. For those who think Neanderthals and modern Humans never hybridized, take a look at this: 
    The man has everything – sloping forhead, prominent brow ridges, slightly receding chin, hairy back, etc.

  28. he does lack an occipital bun, though. He is a hybrid afterall…

  29. I doubt that he’s got any “Neander” genes in him. It’s more of a hyperpituitary kind of appearance[e.g., gigantism] if you ask me. Hmmm, though it’d be interesting to know what his IQ is.

  30. Rietzche, it was offered as a joke, but it makes you wonder if some of the conditions that lead to a Neanderthal look in Valuev weren’t also present in Neanderthals. 
    From what I’ve read, the jury’s still out on whether Neanderthals contributed any genes to modern European populations, though it’s highly unlikely that they contributed any mtDNA or Y-chromosomes. It may be that some adaptive alleles in Neanderthals could have been for selected for in modern populations with only limited hybridization and very little trace of other genes. After all, Neanderthals had a few hundred thousand years to adapt to Ice Age Europe, which population just recently migrating from Africa wouldn’t have had.