Tuesday, 23 July 2013

Let's talk about "Macroevolution"

One of the recent Creationist gambits is the invention of the macro and micro-evolution shibboleths.  This is a convenient way to act like a hypocrite- by accepting "microevolution" they can continue to use modern antibiotics and crops.  By rejecting "macroevolution" they get to cling on to their beliefs.

Like so many arguments used before, this rejecting "macroevolution" depends on a combination of ignorance and dishonesty.  The reason I put "macroevolution" in quote-marks is because as far as biologists have ever been concerned, there is only evolution.  This is the change in inheritable traits (allele frequency) in populations over generations.  There aren't different processes.  The Creationist argument starts on an unsound scientific basis.  (This is usually typified by them being unable to define what "macroevolution" is to me).  Paleontologists sometimes use the term macroevolution but this doesn't really line-up with the creationist term. In this context, macroevolution describes the large-scale changes seen in the fossil record.  In the creationist sense, it usually means common ancestry.


DNA- Advances in molecular biology in the 1980s forced Creationists to invent the 'Macroevolution" argument
Ok, so why have Creationists come up with this argument?  Well, basically because older arguments got over-run by advances in modern biology.  When we could only dimly see changes occurring at the molecular level, creationists would appeal to ignorance.  If we can't see these changes occurring, then they weren't going to buy into evolution of any kind.  Once we showed we could see evolution occurring at the level of individual genes, there were only two options.  Accept that evolution occurs or invent a new definition of evolution and insist this is yet to be proved.  The "macroevolution" argument comes down to the dishonest gambit of inventing a new definition. 

The argument is also intellectually dishonest.  The Creationist concept often boils down to speciation.  They insist that a speciation event must be observed for their concept of "macroevolution" to be tested and proved.  Given we estimate it usually takes 50,000 to 100,000 years for a speciation-process to complete, then really, they're just trying to create a test that is impossible to pass.  Human history isn't long enough (usually) to see a new species evolve.  Insisting we observe in 50 years an event that takes 50,000 is appalling dishonesty.  This isn't about creating tests that are falsifiable (truly scientific), it's about contriving a test that is impossible to pass. 

Nonetheless, we have observed speciation events.  While it usually takes a long time, the 'tail of this distribution' can yield some much faster events.  For example, the sunflower Helianthus anomalus and the groundsel Senecio cambrensis are recently evolved plant species.  They've evolved by a process called polypoloid hybridisation.  And the neat thing about this, is we've replicated it in the lab.  We've tested the observations by seeing if we can duplicate it and succeeded.  These are entire new species as demonstrated by their new chromosome count.  

As an aside, we've also observed new structures evolve.  The Italian wall-lizard Podarcis sicula on  Pod Mrcaru has been observed to evolve a different head shape and size, along with caecal valves in the gut. The change to the gut is a major and novel structural shift in response to the more vegetarian diet of these lizards.

The argument based on "macroevolution" isn't just dishonest.  It's already been clubbed to death by a mob of angry facts.

The argument is also redundant.  What is seldom recognised is that the same advances in molecular biology that demolished the original creationist arguments also took out the "macroevolution" argument.  One of the most important things about biology, is that inheritable traits get inherited.  Genes leave a long trail back in time.  We don't need to observe speciation events.  A very good record of them is left at the molecular level.  The same genetic evidence that can show paternity, also shows we have a common ancestor with the other great ape species. It's just following the trail back. And we're at a point where we're looking at thousands of molecules at a time.  Similarities aren't down to random chance.  The distribution is not uniform but very convergent. Common ancestry makes a very important, very testable prediction- traits will be organised as nested hierarchies.  That is what we see.

The "macroevolution" argument  runs into many other problems.
  1. What is the barrier to new species forming?  The plant-species above show there's no intrinsic barrier.  And we know that populations keep accumulating differences.  If one early ape species had two separate populations 7 million years ago, and ended up today with a similarity of 98.6% in their DNA, are they still the same species?  There is nothing we've found in biology that can stop genetic changes accumulating.
  2. The distribution of non-coding DNA.  Why for example, do we share most of our psuedogenes and Alu inserts with chimps.  It's easy to see why we'd have over 1m identical Alu inserts to chimps if we both had the same ancestor and inherited them.  Because afterall, they're inheritable. Mostly all we can tell about these short, non-coding sequences is they correlate to a bunch of diseases we'd rather not have. Like colorectal cancer.  
  3. How and where do new species occur? Paleontology has pretty much determined that 99% of all species of planet earth have gone extinct. If nothing can evolve from existing species, then there's a pretty big problem left to explain the motives and mechanisms by which new species occur.





11 comments:

  1. Yeah, this is great. I've been planning to write on this myself, but from an education standpoint. If I do, I'll link to you.

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  2. I'd like to add...

    The theist anti-Evos have a thing. That thing is to insist that while changes can become more common though selection pressures, the inviolable line is that one Biblical "kind" cannot become another Biblical "kind." Because God created "kinds" and as we all know, the Big Cheese cannot be overruled. A big part of the so-called "macroevolution" pushback is underlain by this notion of kinds.

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  3. Daddy Love: They've gone so far as developing their own version of taxonomy called Baraminology that accents differences and ignores similarities to a great extent.

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  4. Well said. I've hammered point #1 (no limiting mechanism, no barrier to genetic drift) into many a creationist - if they want to claim there's a limit, they have the burden of proof to support that claim. Until they can, the barrier is just an irrational claim.

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  5. Yes, very nice indeed. Also good of you to point out the difference between macroevolutionary perspectives in palaeontology and the BS use of the term by creationists.

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  6. Yes, very nice indeed. Also good of you to point out the difference between macroevolutionary perspectives in palaeontology and the BS use of the term by creationists.

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  7. Very nice article. I just want to add that the mosquito Culex pipiens evolved into Culex molestus in England in under 100 years.

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