googlef87758e9b6df9bec.html A Sure Word: Trait Adding Mutations? I'll Show You Why More is Sometimes Less

Thursday, June 7, 2012

Trait Adding Mutations? I'll Show You Why More is Sometimes Less

I recently discussed why genetic mutations appearing in organisms isn't enough to rescue the theory of evolution. For a population to “evolve,” mutations would have to add traits that don't already exist in the population. There have been occasions where we have observed mutations that convey a benefit to its host, but in most of these examples, it's easy to see how traits are still being removed from the population. When we look only for examples of “trait-adding” mutations, the list of possible candidates quickly narrows. In this post, so called “trait-adding” mutations will be considered.

Before we begin, let me make a qualifier. As I've said repeatedly, there must be some mechanism that adds traits to a population for evolution to even be possible. Perhaps such mutations exist. Yet even if a convincing example of a trait-adding mutation is found, it still isn't automatic evidence that evolution is true. Consider too that, in spite of our “advanced” knowledge, there's a lot about DNA that we have yet to discover and we've genetically examined only a tiny fraction of the millions of species that are known to exist. We can hardly be sure whether some observed new feature is truly the result of mutation or if it is even “new.” Perhaps it was already present in the creature's DNA. Furthermore, evolution requires an endless parade of novel features. Trait-adding mutations should be the rule or, at the very least, be ordinary. As it stands now, such mutations could only be described as “scarce” or “non-existent.” In summary, trait-adding mutations aren't a fatal blow to creation; if they exist, they only serve to keep evolution in the running as a possible (though still unlikely) alternative.

When considering mutations, it is frustratingly difficult to define “novel” features. I can appreciate how the lack of a clear meaning of words clouds a discussion and I wish I could produce a concrete, objective definition. I can't. Some creationists use the term, “new genetic information” but I've found that term clouds the discussion even further. “Information” has a technical meaning that, ironically, is too broad to be useful here. From a statistical perspective, simply rearranging the letters “JYIL” to “YLIJ” creates new information even though there are no new letters. If we applied that analogy to evolution, we would see that simply rearranging already existing letters does not explain the origin of the letters.

To determine if a mutation is “adding” anything to its host, I've found it best to examine how the mutation conveys a benefit. In my post about blind cave fish, fish being born without eyes is an obvious example of losing a trait. Along those same lines, there are elephants in Africa being born without tusks. Ivory poachers will shoot elephants for their tusks. Due to a mutation, some elephants are born without tusks and the poachers don't shoot them. Therefore, the tusk-less elephants live to reproduce and pass on the tusk-less trait. This is another obvious example of how a mutation can convey a benefit but still not add anything.

Sometimes, mutations cause a loss of function. A defining characteristic of mammals is that they nurse their young. New born mammals have an enzyme in their small intestines that helps them digest milk. About the time of weaning, the enzyme “turns off,” making most adult mammals lactose intolerant. In some instances, though, as seen in many humans, the enzyme fails to turn off which allows the person to continue drinking milk. So the ability for adult humans to continue drinking milk may be “novel” in one sense but it's still the result of the enzyme failing to turn off at the appropriate time. It is a loss of function.

Other mutations sometimes cited as examples of new features involve the duplication or overproduction of already existing traits. A widely known example of this is that sometimes people are born with six fingers on one hand. This may not convey any benefit but it is sometimes cited as an example of a trait-adding mutation. However, extra fingers on a creature that already has fingers doesn't explain the origin of fingers. I would be more impressed if I saw fingers evolve on a snake.

In 1884, Jo Jo the Dog Faced Boy joined to tour with PT Barnum. Jo Jo (his real name was Fedor Jeftichew) suffered from a medical condition known as hypertrichosis which causes the overproduction of hair. Sometimes, overproducing something could convey a benefit. The overproduction of something like pigment could make an animal darker and better camouflaged. However, it's still the overproduction of something that already exists in the animal. “More pigment” isn't novel in an animal that already has pigment.

When I ask evolutionists for examples of truly novel features added through mutation, I overwhelming hear the same three examples: 1) antibiotic resistant bacteria, 2) pesticide resistant insects, and 3) nylon digesting bacteria. Let's look at these in light of what we've already discussed.

In the case of the first two items (resistant bacteria and insects), one must first ask if the critters “acquired” resistance or were they already resistant? Scientists have recently discovered bacteria in a cave dated by evolutionists to be 4,000,000 years old. When tested, the bacteria were found to already be resistant to modern medicine! To quote the article:

The cave, which is coated in the ancient bacteria, has never encountered modern medicine. Amazingly, these bacteria can still fight off different kinds of antibiotics, including synthetic drugs.... 93 types of bacteria found in the cave were tested against 26 different antibiotics. Seventy percent were able to resist three or four kinds of antibiotics. Three anthrax-related bacteria resisted 14 different types of antibiotics. The results suggest that drug resistance is at least millions of years old and not a man-made phenomenon.”

Obviously, the bacteria are not “evolving” resistance to drugs but have always been resistant. How then could drug resistance be considered “novel”? And if drug resistance isn't necessarily novel in bacteria, perhaps the same thing is true for insects. Unfortunately, we cannot test the insects that lived (supposedly) millions of years ago to see if they were already pesticide resistant.

For the sake of argument, let's suppose that these creatures only recently “evolved” resistance. What has changed in them to accomplish this? Antibiotics work by binding with bacteria which disrupts the function of an important protein and prevents the bacteria from reproducing. It's possible for a mutation to prevent the antibiotic from binding with the bacteria, thus making the bacteria resistant. This doesn't necessarily mean there is a gain of features. Consider how handcuffs are used to subdue criminals. If, because of a mutation, a suspect had no arms, the police could not cuff him. So even though the suspect is “resistant” to handcuffs, it still represents a loss of traits.

Finally, there is the example of nylon digesting bacteria. As in the other examples, we cannot rule out the possibility that this feature isn't novel but has always existed – heretofore unobserved. Setting aside that possibility, we can again speculate about what mutation could introduce this “new” ability. In digestion, enzymes help us break down certain substances. We discussed above how infant mammals have an enzyme that allows them to digest milk. Enzymes are specialized and normally only work on specific substances. However, in the case of nylon digesting bacteria, a certain enzyme in the bacteria has lost its specificity and will break down other substances. Here's an analogy to help visualize this: imagine that I designed a machine that pulls weeds in my garden. It's only supposed to pull weeds but the machine becomes broken and no longer recognize weeds. Eventually it starts pulling my flowers too. Some could say the machine has acquired the ability to pull flowers but the reality is that the machine is broken and doesn't function as well as when it was built.

Let me pause here and remind you that feature-adding mutations must occur with some frequency for evolution to be possible. Three examples, no matter how often they are trumpeted, cannot be stretched to demonstrate that trait-adding change is commonplace.

I could say a lot more about each of these but this series has gone on long enough. We can quibble over whether a feature can be called “new” or not but, all in all, none of these oft-cited examples are convincing. In each case, we cannot be sure the traits are even novel. What's more, even if the traits are novel and even if they are the result of mutations, they still likely represent a loss of function. Thus we can see how “more” is really “less.” If these represent the best examples of observed trait-adding evolution, how can anyone be convinced that molecules to man evolution is even possible

Further reading:


Steven J. said...

Regarding antibiotic resistance in bacteria:

There is a commonly performed classroom experiment, in which the experimenter starts a number of monoclonal E. coli colonies in petri dishes. "Monoclonal" means that all these bacteria are descendants of a single original bacterium (in this case, from a strain known to be vulnerable to penicillin).

Half the colonies are allowed to grow for a while and not interfered with; half are exposed to ultraviolet light to increase their mutation rate. Then they are all exposed to some antibiotic. The unirradiated colonies die off; some of the irradiated colonies have survivors which re-found the colony.

That there were antibiotic-resistant bacteria millions of years ago is not terribly relevant; there weren't any in these particular colonies when they were started, so the traits are novel in them.

Note that while antibiotic-resistant bacteria often reproduce more slowly than antibiotic-vulnerable bacteria, they do not suffer from any defects as crippling as the loss of arms would be to humans -- and I seem to recall that, given time, slow-breeding resistant bacteria are displaced by faster-breeding ones.

Note that in a large bacterial population (e.g. in a cave), there will be many mutations, including mutations that confer resistance to bacteria. Mutations are supposed to be random (i.e. mutations for resistance won't be more common just because the environment now has something for them to resist, though they will be more selected for under such circumstances), and should have been turning up for billions of years (though for much of that time, such mutations would have been useless or deleterious).

Note also that many antibiotics are not, themselves, truly novel: the first one, for example, penicillin, has been produced by bread mold for, probably, millions of years. Mold compete in the wild with bacteria for food, so even in an environment in which no one used mold secretions for medicine, there might well be some selective value to antibiotic resistance.

Steven J. said...

Regarding nylon-eating bacteria, comparisons of nylon-metabolizing Flavobacterium with more ordinary strains suggest that the enzyme that breaks down nylon arose from a gene duplication and frame-shift mutation in the duplicate gene (i.e. that this is not a "loss of specificity" of some older enzyme but the production of a novel enzyme of unknown specificity (except that it breaks down nylon).

Whether "loss of specificity" is a gain or loss of "information" is hard to say. To take another analogy, you seem to be arguing that a skeleton key that can open every door in a building is "broken" or imperfect compared to keys that can only open one or a few specific doors. I don't think an information theorist would agree that the skeleton key has "less information," though admittedly I am no expert in information theory.

It has been noted, regarding the "specificity" argument, that we haven't exhaustively tested many (any?) enzymes to see what they affect; it's hard to say whether the ability to digest one new substrate plus one or two old ones means that the modified enzyme is more specific, or less (and if, when gaining the ability to digest some novel substrate, it lost the ability to digest a substrate it used to be able to digest, wouldn't you argue that this is a "loss of function" and "loss of information," so that any change of function can be defined as a "loss of function?").

Steven J. said...

If snakes could be induced to grow fingers, what would that prove? There was an experiment, some years back, showing that exposing chicken gums to a hormone that triggered tooth production, did indeed grow triangular, dinosaur-like tiny teeth; this was taken to indicate that chickens (and presumably most other birds) still have genes for making teeth, even though they aren't used. The chickens weren't mutated, but a mutation that induced limb formation in snakes might simply mean that snakes already had genes for limbs, which simply were normally never triggered.

Tetrapods haven't added a limb, of course, in 400 million years or more. Indeed, aside from repeatedly losing limbs (snakes, some lizards, some amphibians, whales, etc.), we've reduced the original finger complement from eight to at most five (and fewer in many species) per limb. Really novel traits (what a creationist poster to the forum Talk.Origins called "sticky-out bits") are rare; most novelty consists of relatively minor modifications of existing traits or loss or reduction of traits. So it's not clear that we should see really remarkable novelties (as opposed to the occasional striking modification of a common trait) all the time in nature.

Side note, in case you care: snakes lost their front limbs (presumably by gradual reduction in size and complexity) before their rear limbs. This is shown by fossils (there exist several fossil snake species that have hind limbs but not front limbs), analogy (there is, e.g. a genus of skinks -- lizards -- in which one species has four limbs, one has only hind limbs, and one is limbless like a snake), and comparative anatomy of living species (no living snake has even vestigial front limbs, but boas have vestigial hind limbs).