The Science of Evolution - Anti-Evolution Creationism: An Assault on All of Science, in the Name of God
Revolutionary Worker #1221, November 30, 2003, posted at rwor.org
part of 7e, in last week's RW, discussed the arguments of
the 'Intelligent design" creationists. These IDCs do not deny
that the earth may be billions of years old, or even that
species change over time. They insist, however, that their
development must be somehow guided by a divine intellect.
Biochemist Michael Behe, for example, insists that living
creatures and in particular their molecular processes are often
"irreducibly complex"--and could simply not have evolved
without intelligent design. In this second part of 7e, the
author continues to address these arguments from several
The first part of evolutionary biochemist Ken Miller's book Finding Darwin's God is full of examples of actual observable biochemical evolutionary pathways which could easily have undergone such series of step-wise evolutionary modifications before later producing what Behe thinks of as "irreducibly complex systems."
This is no different in essence than the well-documented step-wise evolutionary processes we can see in the fossil record, as we discussed earlier in this series and which Miller also reviews. For instance, there are three little bones in the middle ear of mammals which make up the apparatus that allows people and other mammals to hear. This system fits Behe's definition of "irreducibly complex," because if you remove any one of those bones, all hearing is lost! So how could evolution have come up with enough simultaneous mutations to generate such a complex three-part system "all at once"? Well, that's just it--evolution didn't do it "all at once." Time-ordered sequences of fossils reveal that evolution "built" a mammalian inner ear out of some of the rear jaw bones which existed in the reptile-like ancestors of the first mammals. Reptilian jaws had undergone many earlier evolutionary modifications themselves over time, and the result of some of these earlier evolutionary processes had been that, in some of these old evolutionary branches, the reptilian jaw bone components had (over many generations) moved way back towards the back of the head. And we can also tell, by looking at the fossils, that at a certain point in this evolutionary process, the position and interrelationship of some of those rear jaw bones would have been configured in such a way that they would just have happened to pick up sound vibrations. This wasn't "planned" or "designed" by any outside power--it just simply emerged as a by-product of some of those earlier evolutionary changes which had long been reconfiguring the relative positions of the bones in the rear jaw. But imagine what an advantage it would likely have been like for some of these reptile-like creatures to develop even limited hearing. Natural selection would have been very likely to preserve (and over time to further develop) this capacity to hear (which helps to avoid predators and so on). As stressed many times earlier in this series, such an evolutionary progression is never bound to happen, but in this case we know that it did, because we can see evidence of these changes in the fossil record of extinct species--including in a species of intermediate fossil which has bony parts in the far back of the jaw that still served a function in relation to opening and closing the jaw, but which are situated in such a way that we can also tell they would have picked up on sound vibrations. So this is an example of a more complex system (the three-part mammalian inner ear) evolving out of a simpler one, which fulfilled a different function previously.
Over time, as organisms reproduce, the natural genetic variation found in any living population keeps getting "reshuffled" in various ways, and this occasionally brings forth new inheritable features. Those new features that happen to in some way help individuals contribute more descendants to the next generation (perhaps by helping them get more or better food, mates, or nesting sites, or by helping them to better avoid predators) will automatically tend to get passed on to more individuals in the next generation (simply because they are producing more descendants than the organisms who don't have that new feature) and in this way, over many generations, the new feature will spread to a greater and greater proportion of the population--it's really as simple as that.
The emergence of the more complex (and better hearing) mammalian inner ear out of an evolutionary modification of pre-existing reptilian jaw bones and a simpler hearing apparatus is just one of many examples that shows that Michael Behe is flat-out wrong when he argues that "an irreducibly complex system cannot be produced directly by numerous, successive, slight modifications of a precursor system, because any precursor to an irreducibly complex system that is missing a part is by definition non- functional."
As Ken Miller sums up: "To fashion the three-bone linkage that conducts sound from the eardrum, evolution didn't have to start with a non-working incomplete one-bone or two-bone middle ear. Instead it started with a perfectly good reptile-style ear, which had a single internal bone. Then it grabbed two other bones from a different organ, the jaw, and used them to expand and improve the apparatus." And you can actually see that transition in the fossil record.
Another thing that is important to remember is that geneticists and evolutionary biologists have also known for a long time that sometimes even very minor genetic changes can lead to very big changes in function. This can happen, for instance, when a relatively minor genetic restructuring ends up changing the rate at which some structures (or a whole organism)develops . To use just one example, it is thought that a slowing down of overall rates of development (which could have come about as a result of chance mutations) may have played a crucial role in opening the door to a huge leap in brain capacity and related functional abilities at a certain point in the evolution of our own human lineage. Members of the human species are born much more "undeveloped" and helpless than the infants of other primates, and humans take much longer to develop and mature, but this also goes along with having brains that continue to grow and develop outside the mother's body for a long time after birth and in interaction with the richly stimulating and diverse outside physical and social environment. Thus, what may have started off as a simple genetic modification occurring in an ancestral species of humans--such as a mutation in one or just few genes which just happened to slow down rates of development--seems likely to have opened the door to the tremendous increase in intelligence and behavioral flexibility which is the hallmark of our current human species (all of which would have been strongly favored by natural selection).
Or consider another example: In the plant world there are a number of species of flowering trees which engage in what's called mast-flowering and fruiting. What this means is that all (or most) of the individual trees in a population of such trees manage to flower all at the same time, and generally also end up producing their seeds or fruits at the same time. This makes for an extremely efficient system of pollination and seed dispersal because the mast-flowering and fruiting of so many individuals all at once serves as sort of a great big advertisement to the insect or bird or other species which visit these flowers to obtain food (sugary nectar and/or seeds and fruits) and in so doing end up unconsciously "helping" the plants to reproduce. In visiting the flowers for food, the insects, birds, etc., also pick up male pollen and end up transferring it to the female flower parts where it fertilizes the plant "eggs" and starts a new seed growing. The species of animals which visit the trees to eat some of the fruit end up unconsciously "helping" the plants to disperse their offspring (many seeds go through the digestive systems of animals and are later released in their droppings in new locations).
Pollination and seed dispersal occurs in much the same way in many species in which individuals don't flower or fruit all at the same time, but the point is that mast-flowering and fruiting in some species makes for increased efficiency, as both pollinators and seed dispersal agents can't miss these showy events and often "key in" to the flowering and fruiting schedules of these particular plant species, actively concentrating on visiting these species when they are flowering or fruiting. Of course, the plants and the animals engaged in this complex series of interactions obviously don't "know" they're being so efficient and so tightly locked in a web of such exquisite interdependency, and yet this complex system also didn't have to be planned or designed by any outside force. Such wonders of nature are actually pretty easily explained by the well-known, well-documented and often observed mechanisms of natural selection operating on genetically varied populations of the species involved: the appearance of genetic mutations and recombinations which just happened to "synchronize " the developmental and flowering schedules of some of the plant ancestors would have likely resulted in more efficient pollination and seed dispersal, and therefore allowed individuals which flowered at the same time as others in their population to contribute more descendants to the next generations than individuals which continued to flower or fruit all on their own and "out of synch" with others in the population.
In this way the modification would continue to spread to more and more individuals over the generations through simple natural selection; and once all the individuals in a population of trees started to flower in synchrony, natural selection would also tend to differentially favor pollinators and dispersal agents which happened to be able to detect (and take advantage of) this mast-flowering or mast-fruiting event, and also those species whose own developmental and behavioral patterns happened to be in synch with these events. For instance, some species of insects emerge from their eggs en masse at "just the right time" to take advantage of a brief "window" when a food source becomes available in the plant world. Seeing this, some people might be tempted to think such wonders of the natural world must necessarily result from some kind of "divine plan," but actually all this can be explained by the relatively simple workings of evolution and the entirely natural mechanism of natural selection which, over many generations, unconsciously "sorts out" the naturally occurring and constantly changing genetic variation in a living population, periodically throwing up new inheritable genetic combinations that significantly alter some of the features and functions of organisms in relation to their environments. Any new inheritable features which happen to give a reproductive edge to individuals which have them will always tend to spread (without any conscious design or plan) simply because each successive (later) generation will contain a higher proportion of individuals having these new and reproductively advantageous features.
Natural evolution produces many things that human beings justly consider to be "wonders" (including many examples of apparent "fine-tuning" which sometimes produce an amazingly "tight fit" between different species or between a species and some other aspect of its environment), but this is just testimony to the wonderfully creative powers of naturally evolving systems which produce new things through completely unconscious processes which have been well documented (for the better part of two centuries now) in both the science lab and in the wild. I too find it all beautiful and "amazing"--but it is no longer particularly mysterious.
But, is there some particularity about biochemical reactions taking place at the sub-cellular level that is fundamentally different from any of this? While Behe thinks so, cell biologist and biochemist Ken Miller shows this is nonsense. In addition to the previously discussed example of the biochemical processes in cilia and flagella which allow some cells (like some bacteria and sperm cells) to move through fluids, Miller cites other examples, such as:
This is a complex multi-part biochemical system machinery which is involved in how cells produce energy. In human cells it is made up of six parts, all of which are necessary to make it work. So to Behe this is another example of "irreducible complexity" and evidence of divine design. But it turns out that each of the protein pump's six major parts is closely related to a simpler system found in living microorganisms--in which they are, in simpler and more basic ways, perfectlyfunctional ! There is every indication therefore that the more complex six-part "pump" evolved out of simpler biochemical processes which already existed in previous ancestor lines, where they functioned in somewhat different ways and in a different context, but nevertheless still functioned.
Normally a hormone molecule attaches to a receptor molecule "like a key fitting into a lock." Geneticists have conducted some interesting lab experiments where, for instance, they changed the chemical structure of a "receptor" protein that a growth hormone molecule normally attaches to. They chemically altered (or "broke") the receptor site so that the hormone molecule couldn't attach to it any more. Then they used modern genetic technology to cause five different amino acids in the hormone's own chemical structure to start undergoing random genetic mutations. After allowing this process to go on (all on its own) for some time, they sorted through the new mutated hormone molecules to see if any of the random mutations had "happened" to produce a hormonal structure that might just be able to attach to the "broken" receptor site. Sure enough, random (chance) mutations had happened to produce a new hormone molecule that just happened to "fit" the altered receptor. In fact, this new "fit" was even "tighter" than in the original hormone-receptor combination--it almost looked like the new mutated hormone had been "perfectly designed" for its new function--even though we know for a fact that the new hormone configuration just happened to emerge out of the chance mutations which were occurring entirely without any human or divine designer providing any direction or control to this process or in any way determining what any of the mutations would happen to generate.
One of the significant things about this experiment, as Miller points out, is that "it shows how two proteins, two parts of a biochemical machine, can evolvetogether ." (emphasis added)
Do we know for a fact that natural evolutionary processes can produce even very complex multi-part biochemical systems? Yes, we do. For instance, Miller discusses the example of bacteria which produce an enzyme calledgalactosidase , which enables the bacteria to digest a sugar calledlactose . These bacteria also have a regulatory gene which controls the production of that enzyme. That control gene is "switched on" when lactose is present in the surrounding environment, but it remains temporarily "switched off" when there is no lactose available for the bacteria to feed on (natural selection often seems to favor the evolution of such energy-conservation mechanisms in populations of living organisms--in this case the presence of the regulatory on-off switch means that the bacteria don't waste any energy making the galactosidase enzyme when there is no lactose to use it on).*
But here's where the lactose-galactosidase story gets really interesting: A few years ago a researcher named Barry Hall conducted an experiment in which he chemically "deleted" the gene which made the galactosidase enzyme: so now the bacteria couldn't make the enzyme needed to digest lactose anymore. Then he placed these altered bacteria in an environment containing lactose (which those bacteria could no longer digest), and simply allowed the bacteria to reproduce on their own for many generations. And it just so happened that after a period of time (many bacterial generations) some mutant strains of bacteria happened to emerge which were once again capable of digesting the lactose. But how could this be, since Hall had completely deleted the gene required for the production of the necessary enzyme?
The answer to this apparent "mystery" illustrates some important evolutionary mechanisms at the biochemical level: first of all, as the bacteria reproduced, generation after generation, small genetic mutations started to appear, due to the usual chance genetic "copying errors" that always occur (randomly, in no preset or predetermined directions) whenever living organisms reproduce. At one point, one of these chance mutations happened to occur in a different gene than the one which had originally produced the galactosidase enzyme--but this mutation now allowed this different gene to start producing the enzyme which digests lactose! So now those mutant bacteria could, once again, eat lactose. In addition, in at least some individuals in these same mutant strains, an additional mutation happened to appear in the regulatory gene which controlled the mutated gene which had started to produce the missing enzyme: now the regulatory gene was changed in such a way that it could once again switch the production of the enzyme "on or off," depending on whether or not lactose was present in the bacteria's environment. And then a third change took place: some generations later, some of these same mutant bacterial strains, grown now in a different sugar environment, started evolving additional mutant strains (still through the same kind of simple random mutations which are always happening as organisms reproduce) which now happened to switch "on" the production of a protein in the bacterial cell membranes (known as lac permease) which makes it even easier for bacteria to take in lactose from the outside environments. Imagine how well bacteria which had all three of these mutations must have fared (how well they would have reproduced) in any environment that happened to contain the lactose food source!
In this way we can see that a living population of organisms, which at first could not eat lactose at all, evolved (over many generations) into populations which could easily and efficiently make use of this food source--and this evolutionary process took place through a purely natural and completely undirected and unscripted combination of chance mutations sorted out by non-chance natural selection (since in a lactose-containing environment the bacterial strains which happened to evolve the capacity to digest lactose would have produced more descendants than those that could not eat lactose, resulting in the natural spreading of these evolutionary modifications over the generations). As the evolutionary biologist Doug Futuyma (quoted in Miller's book) summed up: "Thus an entire system of lactose utilization had evolved, consisting of changes in enzyme structure enabling hydrolysis of the substrate; alteration of a regulatory gene so that the enzyme can be synthesized in response to the substrate; and the evolution of an enzyme reaction that induces the permease needed for the entry of the substrate. One could not wish for a better demonstration of the neo-Darwinian principle that mutation and natural selection in concert are the source of complex adaptations." (emphasis added)
Miller points out that this is exactly the kind of really complex multi-part biochemical system that the Intelligent Design Creationist Michael Behe generally considers to be "irreducibly complex" (and which he therefore doesn't believe could have evolved on its own). The way Behe looks at such a system, he would likely argue that it can't function properly without all its parts being present all at the same time (because the protein which helps bring lactose into the bacteria would, in Behe's view, be of no use if the galactosidase enzyme needed to digest the lactose weren't already present; and that enzyme in turn would be of no use in the absence of the regulatory gene to turn it on when lactose is present in the environment; and in turn such regulatory genes would be of no use if the enzymes they turned on or off weren't there in the first place...) So such an intricate multi-part biochemical system is exactly the kind of thing Behe thinks could never have evolved in separate steps spread out over time -- and that, Behe insists, constitutes "evidence" of the involvement of some kind of intelligent designer. But the example we just went through is direct proof that such a complex multi-part biochemical system can in fact evolve completely naturally and all on its own, in a number of steps spread out over time. As Ken Miller concludes about this concrete example: "we know that it was not designed. We know it evolved because we watched it happen right in the laboratory!"
In sum, there is every reason to believe that the evolution of the various complex biochemical systems present today in many living cells evolved in just such step-wise fashion out of different, simpler, but still functional pre-existing biochemical machineries which existed in earlier lines of ancestor organisms.
This biochemical system is one of Behe's favorite examples of a supposedly "irreducibly complex" biological system which he believes couldn't possibly have evolved simply on its own, through merely natural evolutionary processes. The way blood clots in living mammals and other vertebrates (animals with backbones) involves an incredibly complex series of steps--a kind of "chain reaction" (or "cascade") of proteins which causes blood components to stick together and form a kind of plug or "clot" which stops vertebrates from bleeding to death at the site of a wound. I won't even try to spell out all the steps involved in vertebrate blood clotting--trust me, it really is complex! But, as Miller puts it, " the key to understanding the evolution of blood clotting is to appreciate that the current systemdid not evolve all at once. Like all biochemical systems it evolved from genes and proteins that originally served different purposes " (emphasis added).
It is known that much simpler blood clotting mechanisms have existed in the past (systems in which simple clumps of protein fragments functioned as primitive clots, for instance); and in fact we can still find such "simpler" clotting systems in today's living invertebrates (animals without backbones). It is therefore reasonable to suspect that such simpler clotting systems could also have been present in invertebrates which lived long ago, including in the invertebrates which were the ancestors of today's vertebrates. It is also known that such simple and commonplace events as chance gene duplications (spontaneous "doublings" of certain genes, which can occur accidentally in the course of genetic reproduction) could have resulted in genetic modifications in the clotting mechanisms of some invertebrates, leading to improved clotting. This is a development which, whenever it happened to appear, would likely have been heavily favored by natural selection, especially in the descendant vertebrate lines, since the blood of vertebrates happens to be maintained under much higher pressure than in invertebrates. (This means that vertebrates can bleed out much more easily; selection would almost certainly favor the spread of any mutations which happened to improve more rapid and effective clotting under these new circumstances.)
It has been suggested that the gene for one of the most important vertebrate clotting proteins, fibrinogen , likely emerged originally through a simple random "gene duplication" of a gene that was present in an ancestor species but which initially had nothing to do with clot formation. And in fact a gene that still produces a "fibrinogen-like" protein (but which has nothing to do with blood clotting), has been discovered in some living species of invertebrate sea cucumbers. This strongly suggests that the evolutionary modification of a protein which already existed in earlier invertebrate ancestor lines (where it served an entirely different function) is the likely source of the chemically very closely related fibrinogen molecules which today perform a different function (clotting) in their vertebrate descendants.
But do we have concrete evidence that brand-new biochemical functions and processes can emerge through such natural evolutionary processes without completely disrupting pre-existing functions and killing off organisms and populations?
This is an important question to explore, because one of Behe's claims is that complex sub-cellular biochemical modifications are unlikely to have evolved on their own (without a "designer") because, especially at this sub-cellular molecular level, any significant evolutionary modifications would have been too likely to severely disrupt an organism's entire functioning. But is this true?
Consider the fact that molecular geneticists now know that things like simple random gene duplications are commonplace occurrences. And it is apparently often the case that such gene duplications occur without having much effect one way or the other on any of the organism's functions. But if such a gene duplication occurs and a mutation then also occurs in the "extra copy" of the gene, this can result in a new function (such as the new clotting function in a protein that wasn't previously involved in clotting). If such a change happens to provide organisms which have this new function with a reproductive advantage, we know that the new feature will tend to spread to more and more individuals over the generations (by simple natural selection). But if this change takes place only in the "extra copy" of the duplicated gene, this new function can be "added in" without losing the original function of the original gene.
An example of just this sort of thing can apparently be seen in lobsters. Lobster cells have a protein which is involved in nourishing their eggs (the vitellogenin protein). It appears that, at some point in the evolutionary past, the gene responsible for this protein spontaneouslydoubled , and the "extra copy" of the gene then underwent some degree of genetic modification which happened to allow it to play a role in clot formation. But, throughout this evolutionary process, the original form of the gene continued to function: it still continued to be involved in egg nourishment. It is only the extra and slightly modified duplicate copy of that original gene which became involved in the new and additional function (clotting) so there is every indication that this new function evolved without in any way disrupting the original biochemical process (the production of the egg-nourishing protein).
The blood clotting process in lobsters is different than the blood clotting process in vertebrates (which, as a sidepoint, shows that there is more than one evolutionary pathway which can bring forth similar functions). But this example nevertheless shows that Behe is wrong to assume that such step-wise evolution would spell disaster for living organisms: it is a concrete example of how evolution can work to produce whole new functions out of pre-existing genetic material (through just the kind of relatively small and routine changes which are known to occur randomly) without in fact causing the total loss of a pre- existing function, or other major and detrimental disruptions of an organism's overall functioning.
In sum, what is wrong with the "intelligent design" arguments? Everything. They make a lot of incorrect assumptions (including their assumption that it is possible to define some kind of overarching and absolute "irreducible complexity" at some levels of organization of matter); and they don't even seem to understand very wellhow evolution works.
*As a sidepoint, we can see from this example that "on-off" biochemical regulatory "switches" really do exist in various sub-cellular systems. Earlier in this discussion we commented on Michael Behe's absurd idea that an intelligent designer might have packed the very first living cells (billions of years ago) with ALL the genetic biochemical information and processes that would ever be needed by ALL the many different later species of organisms--including those that he admits wouldn't even have appeared until millions or even billions of years later. He imagines that all those later biochemical processes might simply have been kept "turned off" for those millions or billions of years (until it was time to activate them in various much later appearing species) by keeping them under the control of just such an on-off biochemical switch. But again, one of the things that renders this argument so absurd is that all that these inheritable biochemical on-off switches and the inheritable biochemical processes under their control would not have remained intact and unchanged over so much time: they would themselves be subject to repeated mutations and other evolutionary modifications as individuals reproduced and populations evolved over those millions and billions of years!
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