A number of posts have appeared at Uncommon Descent on the topic of macroevolution. Comments here have been appended to other threads, but I thought it an appropriate subject for its own thread.
The posts start here with a link to chemist James M Tour’s blog, on which he posted some personal musings on the creation-evolution debate. Numerous follow-on posts have appeared on UD subsequently, in a rather recursive comments-becoming-posts-spawning-more-comments-that-become-posts manner. I won’t detail them all, but they comprise the bulk of UD threads between 18th and 22nd February.
Tour admits his lack of credentials in the subject, but fundamentally expresses doubts that microevolution (which he accepts) leads to macroevolution. The issue has taken a bizarre turn since, apparently, a couple of UD regulars have offered to stump up costs for Nick Matzke to have lunch with Tour in a meeting that will be witnessed by one of them (it’s his dollar!) but, at Tour’s request, will not be recorded or discussed externally. A personal tutorial. Matzke’s mission, should he choose to accept it, is to prove to Tour’s satisfaction that the extrapolation is justified – that macroevolution is sufficiently explained by iterating the small degrees of microevolution.
I think the problem often boils down to people’s mental construct of one modern group turning into another. A dog could become a fox at a pinch, but a cat … ? Instead, place the forms side by side and draw lines of genetic continuity to a common ancestor. At the node, according to theory, that ancestral population split, not into two families, but into two species. Formally, microevolution is evolution at or below the level of species, while macroevolution deals with broader patterns. This requires a precise understanding of the biological role of species – because a species in sexual forms is not a mere convenience of classification, but is a true biological entity: the breeding population. It also requires an understanding of the role of recombination – in such a population, this enables genes to travel quasi-independently, on units that are smaller than the entire genome. But when recombination between two populations stops, and the barrier has a biological basis, they have become two species, irreversibly. They stop sharing genes, and so drift apart.
At any moment in time, the entire ‘definition’ of a species is held within the genomes of its currently living members. And of course, that is a movable feast. Gene frequencies constantly, unavoidably and often irreversibly shift in a recombining population. The statistical inevitability of this is readily demonstrated mathematically, in computer models, and (over periods unavoidably shorter than the working life of the average scientist) in the wild. Two ends of shifting frequencies are of particular significance: the day a new gene arises, and the day a gene disappears. This could of course be the same day, but with a baseline frequency that can readily be calculated, a proportion of new genes will not be rapidly extinguished, but will ‘sweep to fixation’ – they will become the sole representative at their locus, and it is the existing gene that has been extinguished. Evolution has no ‘memory’, and cannot distinguish old from new. Now, the number of generations in which this is expected to happen typically exceeds the lifetime of a scientist, but if we can demonstrate the idealised behaviour of populations (akin to, and using some of the same maths as, diffusion), and model it in computers, what is it about real populations that renders extrapolation unjustified?
This is, remember, still within the region of change dubbed ‘microevolution’, which Tour accepts. And even ark-friendly Creationists accept that and a little bit more, since proliferation of species – a macroevolutionary pattern – is invoked to explain species numbers. If two populations cannot interbreed, their genes cannot recombine – however recent their ancestry, they have moved into the part of the continuum marked ‘macroevolution’. At its lowest level, then, macroevolution is hardly bigger than microevolution. If populations can change, split populations can diverge. If that divergence is proposed to be limited as a general rule, there needs to be either a clear universal mechanism that stops such change proceeding indefinitely, or definite and widespread discontinuities in the historic pattern we see in fossils or in commonality between modern forms.
One possible ‘anchor’ is that real populations don’t just have a genotype, they have a phenotype. That tends to be the focus of all attention. It is the change in gross form in the fossil record, the morphological divergence among taxonomic classes, that really impresses. And here, it all looks superficially discrete, even to the point where, for some people, that morphology presents a barrier, a drag on indefinite genetic change. While they might accept the logic of iterative genetic amendment multiplying up into major change (think changing a book a letter at a time), the bodies of two current species cannot be connected by a genetic continuum to a common ancestor because there cannot be viable intermediates (think the demand that all ‘transitional’ books must be worth reading). But this amounts to making a judgement about the space of viable organisms, without doing any investigation. Evolutionists are wrong to assume that the space between any two species is fully connected via viable ancestors to a common ancestor, because … well, what? Where do we place the barrier between reasonable and unreasonable extrapolation? We certainly aren’t generally challenged to prove that two individual humans are connected by an audited genetic continuum. Nor that, for example, any two dogs are. Or dogs and foxes. Or dogs and cats? Dogs and rats? Ah well, now … the bigger it gets, the more stringent the demands. Is there nothing we can do to assess the claim of genetic continuity?
Early attempts to investigate the patterns were obliged to concentrate on phenotype. They had little choice; they had no idea how genotype was implemented. Those morphologies converged on nested hierarchies of characters. The perfectly reasonable assumption was that a character resemblance – canine teeth, say – was shared between all dogs because they got it from a common ancestor. And between dogs and wolves because they did also. And between dogs and cats because … well, all of a sudden, some people insist that this explanation be discarded RIGHT NOW … at this remove, extrapolation is a matter of metaphysical bias, not reasonable inference. But no sound rationale is offered to make such a dichotomy between close-branching relationship and more distant ‘common design’ between suppposedly genetically discontinuous groups.
We now have the luxury undreamt of by the early taxonomists, of direct examination of the molecular basis of phenotype – and more, of genotype that has no apparent phenotype at all beyond existing. Precisely how, in Tour’s ‘chemical’ terms, genotype becomes phenotype is not deeply understood – but that it does cannot be reasonably doubted. And we see no discontinuity. The genetic differences between close branches (accepted as common descent) differ only in degree, not in type, from those among more distant ‘macroevolutionary’ categories. The deeper you go, the more scrambled the relationship signal, but this is hardly at odds with the assumption of steady divergence – it is entirely consistent with it. At the limit, the signal would degrade entirely, even in a true genetic continuum, but even so for the most part, we are somewhere short of that point.
It could be argued that genetic continuity does not prove that the change was unguided – and indeed, it does not. But the process which appears to proceed without guidance now, inexorably changing and diverging populations, you’d expect to be in operation wherever and whenever DNA replication is occurring. All you need in principle to achieve all taxonomic categories above the species (discrete categories that are human constructs, not ‘natural’ groups based upon biological interaction) is a process of bifurcation and continuing divergence beyond the node, and viability of all intermediate forms. The appearance of genetic continuity is either deceit, or it indicates that a branching process has been in operation, and all intermediates must have been viable. We don’t need to know the precise steps, nor the selective environment (with or without Intent), to conclude that macroevolutionary divergence is real, and demands no fundamental source of variation beyond that supplied by generational change. With no evidential support at the genetic or the morphological level for an hypothesis of discontinuity between higher taxa, there is no good reason to adopt one.
Much of science consists of lines of reasoning, with a bit of empirical investigation thrown in. It’s that last bit that you Creationists don’t do.
Macroevolution is definitional, not empirical. Regardless whether or not it actually occurs, it is what would happen given extended periods of population change with branching. If you think evolution can occur within a ‘kind’, then you accept macroevolution, as defined, as an empirical fact – “evolution above the species level”. You just have two subdivisions of macroevolution – the bit that you can make fit with your holy text, and the bit you can’t.
What things look like, and what that ‘suggests’, are irrelevant. If you can’t place those ‘boundaries’, other than just employing “I-reckonism”, your opinion is simply that. The genetic distinctions between ‘kinds’ are exactly the same as those within ‘kinds’. Kinds, as delimited regions of ‘organism space’ that can neither be entered nor exited, are a pretty feeble attempt to create consilience with your holy text, and there is absolutely no evidence for them, and plenty of evidence against.
Something of a shell game is going on at UD over the various possible interpretations of ‘macroevolution’. All definitions boil down to the general case of evolution on broader scales than simple within-species processes, but an awful lot of words are expended (many of which, I confess, I did not read) attempting to justify Tour’s belief that ‘the emperor has no clothes’.
What I did glean is an attempt to make capital out of the fact that some people mean iterative microevolution, whereas others point to mechanisms operating that aren’t strictly microevolutionary. Nonetheless, all mechanisms act upon the same populations of replicators in which microevolution is the means of generating change. I think an analogy with fluid flow is appropriate. Fluid molecules flow under physics, which both forces and restricts flow. Where constrained, they follow channels. The mechanism of movement down these channels is ‘micro-flow’. Add a baffle, and the processes of microflow operate either side of it, independently. That baffle may lead to a subsequent rejoining, or be a permanent. branch point.
One group of people may regard ‘macroflow’ as being the longer-term displacement of fluid along a particular course. Another may insist that mechanisms of stream bifurcation are mechanisms of ‘macroflow’. For their particular purposes, they are both right. But neither is invoking a means of motion other than ‘microflow’.
The ‘flow’ in generative processes is a chemical process – iterative DNA replication. But the mechanisms of channelling are not. Processes that cause extinction of the middle of a range, for example, can in conjunction with divergent microevolution cause speciation. There is no coherent way a chemical explanation can be provided for this, other than replicative chemistry and its subsequent ‘channeling’ by emergent forces.
The definition that ID people appear to favour is “the bits of evolution for which we have no data”. Explain them! A major organ, say, for which a transitional series is absent. Essentially, for the evolutionist these are sections of genetic flow that disappear ‘underground’. We can detect (via common descent analysis) a genetic continuum. But no, we want the actual series of changes in that continuum, if you would be so good, Darwinists. Selective advantage with respect to long-dead alleles would be nice too. In chemical terms.
ID is and always has been the argument from ignorance. The places on where map where dragons lie.
And of course it’s worth noting that these are not the same levels of evidence that they demand from ID. Yet they uncritically accept ID.
Double standard much?
As KF is wont to say, selective hyperskepticism……
Allan Miller
SCIENCE is not and is not to be lines of reasoning!
Its about hypothesis being demonstrated by testable invesygation and only then can a scientific theory be asserted!
The complete opposite of mere hypothesis/lines of reasoning(however reasonable).
Why do evolutionists think lines of reasoning count as scientific investigation??
A creationist would say because they have to!
You said macro is WHAT would happen!
Again this is just a line of reasoning. One easily can see this would not happen because the great biological differences would not be easily or at all breached.
Micro would happen even if macro could not!
it is not evidence for macro because micro can happen.
By the way micro probably happened very little!
So how do you get from the few things (relatively) off Noah’s Ark to the observed species (400,000 species of beetles alone) we actually see in only a few thousand years, if even micro “probably happened very little”?
Seems you need faster evolution then any Darwinist ever claimed could happen.
These details are speculative , whether right or wrong.
The great point is that evolutionism has truly tried to turn into a scientific fact what is in fact a mere line of reasoning however reasonable.
I say it ain’t one bit reasonable but first things first.
Macro evolution is not evidenced by micro evolution.
If macro evolution never happened it would also be that micro evolution did.
Its all about lines of reasoning and nothing with scientific investigation of biology.
Be persuaded by the evidence and not the hypothesis.
OMTWO
Your right about creationism needing a mechanism.
However this is unrelated to the merits of a evolutionary mechanism.
To me its all about innate triggers easily morphing biology into what is needed.
To me the great clue is human beings.
Explain, for either side, the great differences between the peoples in colour, shape, etc etc and one has explained the how of biological change.
Its staring us in the face.
Toronto: “If however you are right, then Upright BiPed is wrong when he tries to reduce biology to a simple computer model. “
In order to get a sense of where you stand, do you believe that biology can be modeled as a computer that processes “information”?
This is ID’s main premise and without it, all arguments based on the UPB, ranging from Dembski to kairosfocus and Upright BiPed, fail.
Where do you stand in relation to them?
Robert Byers,
You think reasoning does not come into science? That is an odd stance. One has to connect empirical observation with lines of reasoning, and these suggest in turn other avenues one could explore. We don’t have the genome and fossil imprint of every organism that ever lived to hand, so we must investigate using the material we have, which is inevitably patchy.
You fail to explain the universal pattern of common descent, which does not stop at species boundaries. Don’t say “common design”. That is just a line of reasoning. Unless you can offer an empirical means to distinguish those parts of genetic congruence that are due to Design from those due to Descent? Your barking baraminology requires macroevolution – evolution above the species level – to get a few million species from the contents of the Ark.
Congratulations. You have discovered variation. Now, if you can only work out what causes variation, and what inevitably happens to variation in a replicating population, you will have discovered evolution. Someone else has dibs on the idea, though.
Robert can speak for himself, but I understand he is YEC, not ID. It doesn’t much matter if arguments fail, when your source is infallible.
I think something that doesn’t get mentioned enough is that evolution is an observed phenomenon, and biological design is not.
Despite all the bluster, no one can predict the usefulness of a mutation and eliminate the need for trial and error in biological design.
Anyone in the design movement that disagrees is free to provide a ounterexample.
They could take up the challenge I presented to gpuccio. Tell me ho the designer would know which of the early mutations to preserve from the Lenski experiment.
The ‘purpose’ of most assumed Design is enhanced survival in the environment. Something that can of course be achieved non-intentionally by simply chucking variants at that environment. The result would be common descent from the most successful original, with intent in the choice of evolution as a methodology, rather than in the mutation. But the ‘Common Design’ crowd insist that genetic relatedness is both a fact (within ‘kinds’) and an artefact (outside them). Maybe the Designer doesn’t know what will happen within ‘kinds’, but edited his blueprints to make them …?
Evolution would certainly be a potential design methodology. Without it – a world fully-formed containing ‘poof’-ed Survivors – we’d have the odd situation where impressive adaptations are deliberately tuned to foil each other. You want falcons to be effective predators? Don’t waste time giving them keen eyesight; make their prey purple! You want the prey to be good at surviving? Make the falcons blind! One could, of course, invoke Multiple Designer Theory, if one were desperate.
My question is about knowing what a novel sequence will do, both at the molecular level and at the ecological level. I don’t think anyone has demonstrated the ability to predict what a given sequence will do in terms of folding or in terms of regulation.
Demonstrating that you have control of your materials would seem to be the first requirement of any design hypothesis. We certainly don’t see engineers designing products without knowledge of their materials. At least not successfully.
So before anyone can assert that Design is the best explanation of biology, one should demonstrate that Design is possible.
Gpuccio tried to clear this up by asserting the Designer could use intelligent selection, but of course this would simply be a special case of evolution.
Flint, I’ve thought of a visual way of representing the creationist concept. Make an X-Y axis graph. List the most simple species of animal (or plant) as close to 0 as possible. List all immediately related species out along the X-axis. Above that simple organism, list another simple organism and all its relatives out along the X-axis. Keep adding more complex species up along the Y-axis. Note that in the creationist model, nothing along the Y-axis is related.
This is why they see micro and macro evolution as separate concepts. To them, Macroevolution is a completely different dimension of reality.
Please demonstrate, provide evidence for, show a citation to the literature for an ” innate trigger”. that causes “easy morphing” that can create tens of thousands of species in thousands of years.
Or admit it’s evidence free speculation that’s required to get your “theory” to work.
Knowing you, you’ll do neither.
No one can direct me to a textbook on macroevolutionary theory? Really?
Here I am, someone who would love to educate myself on the subject of macroevolution, but there’s no standard textbooks on the “field”?
So why is Nick Matzke whining?
Allan Miller:
Is it? Isn’t that what’s in dispute?
Nick M. seems to think it’s entirely different.
Look, I’m just in search of a textbook. Do you have a specific text in mind that you think presents an adequate coverage of macroevolution?
There are no “simple” species.
petrushka:
Better yet, let’s assume that design is not possible and move on from there.
OMTWO:
That is an argument I often use against YEC’s. Their theory demands hyper-evolution. They cannot coherently argue against evolution while at the same time arguing for evolution.
OMTWO
Its a hypothesis and based on biblical boundaries and observation of differences in biology.
It could only be this way about people.
Anything else needs evidence if it claims to be a THEORY!
Shouldn’t be hard if the evidence is there!
DNA_Jock:
I did concede that your question
was slightly less incoherent. And I answered it.
Where?
OMTWO:
There is plenty of evidence for “radiations” including the “Cambrian explosion.” Pick one.
Those “radiations” are not evidence for an “innate trigger”. that causes “easy morphing” are they now? As that’s what you are trying to claim please provide evidence!
Neither are they evidence for ID at any level.
So what’s left Mung?
And BTW Mung, was the “Cambrian explosion” measured in thousands of years then?
Also Mung, please note the question marks. Those typically indicate questions that typically you might answer to support your point. I don’t expect this from you however, just so you know, so don’t feel bad.
Who does that? Science is about what you have evidence for.
When you present evidence for design it will be considered.
What’s in dispute is not easy to discern because lots of people who don’t know anything about the topic think somehow that their opinions matter.
Therefore ID. Yes, we know….
Where does this leave the “Intelligent Designer” then?
When exactly do you argue intervention from that entity is required?
Good for you. Let me know how that all works out for you.
Mung,
You asked:
“But must not macroevolution be true in order for common descent to be true?”
You got two detailed answers, with links. You are yet to respond.
So when you whine about your “macroevolution book” are you really surprised that nobody really is bothered to answer? You’ve shown quite clearly that you are not interested in the answers that people give to your questions.
If you were you would have responded to the answers that you got.
So it’s obvious that you are not asking anything with honest intent. So don’t be surprised when your charade wears thin and fewer and fewer people bother to reply.
petrushka: “So before anyone can assert that Design is the best explanation of biology, one should demonstrate that Design is possible.”
Mung: “Better yet, let’s assume that design is not possible and move on from there.”
This is why people like Mung are important.
They show how useless ID is even to IDists themselves.
When given an opportunity to give a few sentences explaining a necessary component of ID, he bolts, but not before asking for a complete book from the opposition!
Mung makes our case every time he shows his lack of understanding, and that’s on both sides.
When Mung talks about “design” he fails to note what “design” he is talking about.
Design of life, design of DNA, design of bodyplans etc etc.
We’re left to fill in the blanks. So when Mung says that we should assume “design” is not possible then I can’t even agree with him if I tried.
Of course “design” is a possible option. How can it be ruled out? For a start it’s too vague to rule out anyway until you can give me something more specific then “design” Mung.
Can you tell me something specific that I can rule out please Mung?
Evolutionary Biology by Douglas J Futuyma.
I honestly wasn’t being evasive, but seeking out an evolutionary textbook appropriate to your particular background shouldn’t be too difficult to do on your own behalf. My fundamental point is that I think it important to properly understand ‘microevolution’ before, or at least in tandem with, trying to understand the broader patterns and the evidence for evolution’s role in them.
I haven’t seen anything from Nick Matzke that says or implies that he thinks ‘macroevolutionary theory’ is anything other than a topic within evolutionary theory.
The Cambrian explosion is marked by (relatively) sudden appearance of organisms with hard parts in the fossil record. It probably is a radiation of sorts, if the spread represents colonisation of empty niches or displacement of prior incumbents.
But the facts of the geology are only evidence for those gross forms, not any innate trigger. It’s like saying water has an innate trigger because it flows into valleys when a dam breaks.
There could be innate triggers, but there are problems with such an idea. The idea that (say) hard-shelled prey appeared because their progenitor genomes were awaiting the environmental cue of hard-biting predators would be far-fetched. How many environments would need to be potentiated within a primitive pre-Cambrian genome? And how do you protect them from up to a couple of billion years of mutational degradation, awaiting their onstage call?
Mung,
You quote me thus:
And asked:
Yet my original post read as follows:
The sentence “Changes…genes” was the response. That you missed this shows an impressive failure in reading comprehension.
Now, if you are actually interested in learning something about single-celled organisms, I can walk you through how “Changes…genes” explain the three different cell types in S. cerevisiae, which differences are complex compared with the “macro-evolutionary” differences between S. cerevisiae and S. bayanus.
If you feel the desire to complain “but those are trivial, micro-evolutionary changes!”, then you are making my point for me: even such “micro” changes are appropriately explained at a higher level than mere biochemistry. To re-iterate my question to you:
Even if you could do it, it would not be a very illuminating explanation. Hence the incoherence of Tour’s request.
a non-YEC responds on their behalf
The “most simple organism” is a relative assessment compared with all other organisms, not some absolute measure Mung. But, even if you say all organisms have the exact same complexity (which, oddly, would contradict the basic argument for ID), the graph would still reflect creationist thinking. Either way it works, so I have no idea what the purpose of your comment is.
Note – I’ve moved certain posts pertaining to Robert Byers’s views to his own thread, as they aren’t particularly germane to this specific topic.
Hi.
Pardon me if this is irrelevant or off topic. It keeps coming into my mind as I read the discussion that the relatedness of humans and chimpanzees should answer the whole Micro-Macro evo debate. The DNA is sequenced. Is it not just a handful of gene differences that change us from chimps and bonobos? We share many genetic defects like endogenous retroviruses and the non-functioning gulonolactone oxidase gene for vitamin C production. If an intelligent designer stepped in to make us different from chimps, why would all these genetic fossils be kept? (if there are more examples, I’d like to know them)
I’m not a taxonomist or geneticist (nor did I sleep in a Holiday Inn Express) but with the level of genetic homology we see, wouldn’t it be more correct if we were placed in the genus Pan.. Pan sapiens? Are we not the third chimpanzee? Is it not chauvinism that keeps us from seeing our real place in the animal kingdom? Would not an intergalactic taxonomist place us in the genus Pan?
The Third Chimpanzee is indeed is the title of a book by Jared Diamond, and it’s not just a catchy title. When he wrote it, DNA hybridisation ‘melting point’ analysis was the method by which DNA relationships were determined – single strand DNA from two species will form duplexes, and the closer the sequence match, the tighter they bond.
We have since developed more sophisticated techniques, and they too point to a split not too long ago – c6 million years. It then depends on criteria. Strict time-based criteria for genus attribution would arguably favour a single genus (chimps would be Homo by convention, since that is the earlier named genus), but Pan/Homo are on the cusp.
Character methods might favour a lump or a split depending on the character chosen. All taxonomic categories except species (and even then excepting only one of the many definitions of species) contain an element of subjectivity, since they do not have a fundamental biological basis.
The basic issue over history is trying to create discrete categories from a continuum. But for the sexual organisms alive at a given moment, there are only two taxonomic categories of interest – things you can mate with, and everything else. When the former set subdivides, there lies the main dividing line between the ‘micro’ and the ‘macro’ – the region where the distinction is, initially, barely perceptible. Some people apply the distinction to divisions of the historic continuum instead, and then the boundary is blurred. They’re correct too – it is simply a definitional distinction.
Dave L,
My personal favorite demonstration of common descent would be the mutations in our olfactory receptor genes:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC152291/table/T1/
Hard to escape the conclusion that we are just another primate with a rather poor sense of smell.
:~)
Thanks Allen & DNA_Jock.
This is the crux of the matter. The point of the ID argument is, we are the intelligently designed crown of creation. The fact is we are primates with all the rights, privileges and benefits of family membership. In the deal we also get the defective and haywire genetic material which makes life hell for many of us. Just tell someone with two copies of hemoglobin S, living with the agony of RBC sickling crises that an intelligent designer helps us fight malaria when we get one copy of the S gene but they are screwed cuz in their parents roll of the dice gave them two copies.
The finger of the ID-er is just too fickle.
Your objection to reasoning is well known. All scientific theories use reasoning. Evidence cannot produce a theory on its own. Someone has to make sense of the evidence.
Try another objection. Maybe something about polar bears.