False Arguments #23 & #24: The Sufficiency Of Microevolution Tropes

There are two equal but opposite errors I see again and again in ostensibly educated discussions about evolution, and both of them involve ignorance about what scientists mean when they use the words macroevolution and microevolution, (hereafter Ma and Mi, respectively).

The creationist or believer who maintains that Ma is impossible or unproven shows an ignorance of science paralleled only by the atheist or skeptic who maintains that such is untrue because Ma is just cumulative Mi. These are what I call the sufficiency of microevolution tropes, and both of them distort scientific accuracy concerning the facts of evolution.

As genuine thinkers, we need to know what to look out for here, so first let's discuss the terms.

Coined between World Wars by Russian entomologist Iurii Filipchenko, misunderstanding of the terms Ma and Mi themselves is perhaps the single most responsible factor for the problems related to these tropes.

In evolutionary biology, Ma is synonymous with cladogenesis and refers to change at or above species level. I believe this is what Bernhard Rensch referred to as, "supraspecific evolution." Mi, then, becomes synonymous with anagenesis, a term that doesn't get used quite as much anymore, and refers to any evolutionary change below the species level.

It should be noted that these are not the only things a person can have in mind when throwing these terms around. Some people use Ma in a more figurative sense, as if to denote the entirety of biological evolution over time. Others use Ma in a more mathematical sense, as if to denote the entirety of accumulated Mi. Both uses are misleading, the former because Ma can only naively be described as Mi + time, and the latter because Ma can only naively be described as nothing more than cumulative Mi.

Scientists, creationists and laypeople all use the terms Ma and Mi to mean different things at different times, and as with any other issue of scientific debate that descends to the general public, precision, clarity and consistency of terms are of paramount importance if we want to have a productive or even civil discourse.

False Argument #23: "There's no evidence or proof for Ma. Mi is possible, but not Ma."

This is what we could reasonably call the insufficiency of microevolution trope – the creationist or believer's version of the error – typically used as a wedge to force gaps in evolutionary theory that are then claimed to be explainable only via divine intervention. The creationist or believer claims the gaps in scientific knowledge constitute evidence for God. This is the reasoning behind much of Intelligent Design theory, and also Michael Behe's concept of Irreducible Complexity. Critics call these arguments from ignorance, also referred to as God of the Gaps arguments when made in this particular context.

Although rhetorically successful – and maybe God did drive some component of evolution that woudn't of naturally occurred – still, in my opinion, these arguments lack substance in both science and logic. The proponent views things in the traditional Linnaean framework by which type or kind constitute immutable boundaries that cannot be crossed via accumulated Mi. These boundaries are sometimes referred to as the fixity of species. Not all creationists believe in the fixity of species, and if you really want to get down to it, nor do all creationists interpret fixity of species similarly. These are other common sources of strawman skeptical argumentation. Many evolutionary biologists dispute that fixity of species exists at all. I would say that evolutionary stasis is a different concept.

Regardless, the point is, that there is no proof for Ma is already a well-disputed claim, and that's why the majority of evolutionary biologists and paleontologists consider this a false argument. Even so, it was originally founded on solid reasoning given the scant evidence of Darwin's time, and we can trace the essence of the argument all the way back to Fleeming Jenkins, one of Darwin's earliest and more personally-feared critics. As Gould offers hypothetically in Structure's relevant passage, "…suppose that species function like glass spheres with a modal configuration at the center and unbridgeable limits to variation representing the surface."

By no means do I imply that Jenkins was a creationist, but is this not the same argument today's creationists still use to deny evolution? Is there a successful counter to these any of these facts as presented?

False Argument #24: "Ma is no different than Mi, Ma is just Mi over time, Ma is cumulative Mi." Each of these and their many, many derivatives are the sufficiency of microevolution tropes – the atheist's or skeptic's version of the error – typically used as rhetorical oversimplification in response to the creationist version of the trope we just deconstructed. Critics call these scientifically inaccurate oversimplifications, and noting the legitimate distinctions between Ma and Mi does not entail the claim that origin of higher taxa requires some non-existent mechanism:

"…Ma (cladogenesis) follows different rules than Mi (anagenesis), and these differences are most noticeable in the fossil record cited by Eldredge and Gould as the basis for their theory of punctuated equilibrium. In particular, the basic program that energized the modern synthesis – that is, the reduction of all significant evolutionary mechanisms to a series of linked mathematical models, based on grossly simplified reductions of complex biology to quasi-Mendelian point-like 'particles of inheritance' (changes in which drive the variation and divergence of phenotypes) – is impossible to apply in any coherent way to Ma. The modern synthesis was essentially a 'Newtonian' program, whose proponents assumed that the underlying law-like processes (i.e. Mi) are (like physics) both ahistorical and universal. However, it is now becoming clear that the emerging science of Ma is both irreversibly historically contingent (and therefore not reducible to mathematical formalisms) and driven by fundamentally different processes than those underlying most of Mi. …And so, rather than Ma being simply Mi (i.e. selection and drift) extended over deep evolutionary time, Ma is a genuinely different process that occurs in the absence of most microevolutionary processes (i.e. the relaxation, not the intensification, of natural selection)."

Allen MacNeill, Senior Lecturer, The Biology Learning Skills Center, G-24 Stimson Hall, Cornell University. November 15, 2007 at 9:00 pm.

Under no circumstance should it be called scientifically accurate or intellectually progressive to wave the creationist away and tell him or her that Ma is just Mi over time, or scale, or anything even remotely like that. If by Ma we mean cladogenesis events, then Ma is most certainly not Mi over time – if by Mi we mean anagenesis events. If by Ma we simply mean "all of evolution throughout time," even then the claim still fails, because the history of evolution is better represented as a rocky road cunningly traversed than a series of smooth intra-species gradations. Cladogenesis events occur more rapidly than anagenesis events, and can occur with only one individual in only one generation, as almost all organisms but mammals can reproduce asexually. So we cannot say that Ma is just Mi over time, or scale, or anything similar. The latter reminds one of Darwin's original gradualism as extrapolated in Origin, before the introduction of Mendel's genetics into the theory, and before paleontologists like Gould, Eldredge and others painted the complete picture of the fossil record.

"If we could track a single lineage through time, say from a single-cell protist to Homo sapiens, then we would see a long series of mutations and fixations as each ancestral population evolved. It might look as though the entire history could be accounted for by microevolutionary processes. This is an illusion because the track of the single lineage ignores all of the branching and all of the other species that lived and died along the way… There is legitimate scientific debate about whether Ma is more than just lots of Mi or whether Ma encompasses mechanisms not seen in Mi. It’s the sufficiency of microevolution argument. I happen to be one of those scientists who agree with Stephen Jay Gould that there are many levels of evolution (hierarchical theory). Thus, Ma cannot be sufficiently explained by lots of Mi. There are other things going on at the higher levels."

Larry Moran, Professor of Molecular Evolution, University of Toronto

While it is common to see atheists and skeptics correcting creationists and believers on their version of the false argument, what the former seldom realize is that their responses to the latter are often as naive and scientifically misleading as the latter's original arguments.

I say that regardless of whatever we personally believe, if we are to be scientifically accurate, we must tell the full story behind the sufficiency of microevolution tropes – or we should tell no story at all.

12 Comments

  1. nal says:

    … as almost all organisms but mammals can reproduce asexually.

    What? All but a few animals reproduce sexually.

    Cladogenesis events occur more rapidly than anagenesis events, and can occur with only one individual in only one generation …

    This sounds a lot like saltation. A now discredited idea.
    This post has got me investigating this subject a lot more. I’ve got more reading to do.

  2. Brad says:

    Sexual mammals account for only a small piece of the mosaic biosphere. Simpler asexual organisms are still around and ubiquitous in comparison. (CL was talking about organisms, not animals.)

  3. nal says:

    cl mean to say animals instead of mammals. Still reading. There’s a lot to understand.

  4. cl says:

    nal,

    cl mean to say animals instead of mammals.

    Yes, sorry if that was unclear. Most organisms and plants reproduce asexually. Most animals reproduce sexually, as you note.

  5. nal says:

    Cladogenesis events occur more rapidly than anagenesis events, and can occur with only one individual in only one generation, as almost all organisms but mammals can reproduce asexually.
    First-Degree Inbreeding Facilitates Chromosomal Speciation
    Not sure where chromosomal speciation fits into cladogenesis, but it’s interesting that a similar (hypothesized) mechanism can be found in animals that reproduce sexually.
    I agree (now) that Ma is not just accumulated Mi. Many of DD’s commenters got this wrong (me?). It’s been an education and I wish I had more time to better understand the technical aspects. Also, I don’t see anything in this discussion that argues against the theory of common descent.

  6. nal says:

    http://evolutionlist.blogspot.com/2006/11/hypothesis-first-degree-inbreeding.html
    My href for “First-Degree Inbreeding Facilitates Chromosomal Speciation” wasn’t allowed.

  7. cl says:

    nal,
    I’m really sorry about the HTML problems. It’s a TypePad thing I have no control over. I can see that your link did post, however… so it seems like maybe it worked? Don’t lose hope! TypePad’s not usually this whacked out. Maybe it’s the good weather over here.

    **I agree (now) that Ma is not just accumulated Mi. Many of DD’s commenters got this wrong (me?).

    I thought so, too, but I didn’t think you were one of them. I think I really got the short end of the stick on that deal, but oh well. So it goes.

  8. Freidenker says:

    Alright… That was… fairly confused. The Mi-Ma “fallacy” you mention is something I find completely harmless. In fact, it’s less than harmless – it’s useful. It’s a GOOD lie. Obviously, if one wishes to get deeper into the matter, he’d have to realize that certain mechanisms other than drift and selection can be in charge of evolution – but as far as the raw material for evolution: drift and selection do just fine.
    It’s not enough because it doesn’t explain the *evolution* per se of many taxa – but without these two, evolution is impossible.
    This may appear a trivial argument, but it’s not – when you say that Ma is cumulative Mi – you’re not exactly lying, you’re just missing out huge chunks of the story. A lot of evolution occurs due to some cataclysmic event (adaptive radiation springs to mind – there’s no explanation for 20 species of Finch without the invasion of a bird to an island)
    But without years of drift and genetic innovation, it’s possible that Finches would never have had the plasticity to evolve so fast at all…
    As for PE – the best way to explain the “difference” between PE and gradualism is like this: when you have branches that branch out at *very* small angles – to the paleontologist’s eye – it’s impossible to distinguish very small angles from vertical branches – which makes it appear as if certain taxa pop out of no where.
    This is just a consequence of the enormous depth of time surpassed by the earliest fossils. The Cambrian “explosion” took millions of years. Hardly an explosion. Imagine hundreds of millions of years of non-fossilized life – lots of Microevolution right there –
    and then, wham, you get teeth, osseous phyla and a frenzy of evolutionarily experiments…
    Is this not gradual? It sure is – it’s just gradual – faster. :-)

  9. nal says:

    FYI. Over at Pharyngula, Prof. Allen MacNeill gave some of the commenters a class on the “macro = accumulation of micro” argument.
    http://scienceblogs.com/pharyngula/2009/05/i_get_email_from_peter_heck.php#comment-1644343
    There was one commenter who already had that class.

  10. nal says:

    FYI. Over at Pharyngula, Prof. Allen MacNeill gave some of the commenters a class on the “macro = accumulation of micro” argument.
    http://scienceblogs.com/pharyngula/2009/05/i_get_email_from_peter_heck.php#comment-1644343
    There was one commenter who already had that class.

  11. cl says:

    Thank you, nal. It’s funny how people work – a person who withholds his credentials gets completely ridiculed and mocked for saying the same exact things as professors, biology postdocs and microbiologists. The chips will fall where they may, I suppose..

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