Though the term "macroevolution" is indeed often bandied about by creationists
, it nonetheless offers a mildly useful distinction. Microevolution
refers to small changes that look like they took only a few steps. Macroevolution refers to changes that appear to be large in scope. The two terms are, of course, innacurate in the sense that evolution
is not really discrete
process: there are no firm boundaries between species
, and therefore the difference between microevolution and macroevolution becomes highly subjective
The distinction is useful in this regard: very, very few people contest microevolution. It has been observed in a number of species in a number of conditions, and most reasonable folk accept the existence of such small changes: the change in finch
s' beaks, the resistance of a population of bacteria, and so on can be observed with your very own eyes.
Macroevolution is a bit of a thornier issue. By Darwinian
theory, macroevolution will take a great deal of time to occur - far more time than any man could spend observing. Certainly we can see speciation
, but we will never see anything as significant as reptile
s evolving into mammal
s or what have you. Several microbiologists
in particular seem to question it, among whom are Michael Behe
and Michael Denton
. Both have written highly accessible books on the subject. Their analyses of evolutionary theory seem valid on its face; however the alternative offered in Behe's book, Darwin's Black Box
, seems unconvinving: Behe ultimately winds up arguing that an intelligent design
er was responsible.
The basis for macroevolution is the extrapolation of microevolution. . .that the many small changes of microevolution guided by natural selection
will ultimately cause one species to diverge into another remote species over great amounts of time. The arguments raised by such critics against macroevlution are several.
Among these arguments is the classic claim that there is a paucity of transitional fossil
s in the fossil record
: Considering the incredibly diverse nature of life on Earth
, it does seem like there would be more transitional fossils than there are. Now, there are certainly many examples of seemingly intermediate animals - that is, animals that seem to bridge the gap between, say, birds and dinosaurs
or reptiles and mammals
. But nonetheless, there do seem to be fewer than expected. Glenn Gould
and Niles Eldredge
came up with the theory of Punctuated Equilibrium
to explain this lack.
And yet Denton, at least, goes on to attack the nature of the seemingly transitional animals that we have gotten our hands on so far. I am no paleontologist
, so I cannot evaluate the validity of his claims, but he says that the classic examples of transitional animals are far from convincing. For example, the duck billed platypus
seems to exemplify the transition from reptiles to mammals in that it has some reptillian characteristics, like laying eggs, and then many more mammillian ones. And yet Denton says that the mammillian characteristics and the reptillian characteristics in the duck billed platypus are fully formed - that is, from its reproductive system
, it is fully reptillian; from its other characteristics, it is fully mammillian. It does not seem to be an animal whose traits are somewhere on the slow road between reptile and mammal, as evolutionary theory would suggest - rather, it is part entirely mammmal and part entirely reptile. Wild. Crazy. Definitely weird.
Behe, a biochemist
, has spent a great deal of time arguing that life could not have advanced to its current complexity through little changes because complex life has so many "black box
es," or what he calls "irreducibly complex systems." These are systems which he claims that are made up of so many very specific, very well matched parts, removing or changing any one of them would make the system stop working. A system like this, Behe argues, couldn't form by making random little changes, nor could it advance to greater complexity by making random little changes any more than a meaningful sentence could be made by randomly combining letters. There is a certain level at which the removal of any one thing will make the system break down, and this fundamental level is composed of so many different elements, its creation by random changes directed by Natural Selection is all but impossible. Examples he offers include the immune system, blood clotting, and other complex biochemical systems.
Well, those are some of the classical, nonreligious arguments against macroevlution. As I've said, I am not a biologist
or a paleontologist, so I lack the ability to verify the accuracy of their data. But taking such data as accurate on its face, it does leave a few questions that evolutionary theory has yet to answer. Nonetheless, the model evolutionary theory offers seems rather sound to me, and therefore I object vehemently to anyone who would have it thrown out entirely; nonetheless, it does seem like there are aspects that need further explaining, or, at the very least, more information that must be gathered.