Evolution: Teach the WHOLE theory

apple-halves“Evolution by natural selection is one of the best ideas in all of science. It predicts and explains an incredibly wide range of biological facts.” So says a Wall Street Journal article, which ponders how we can teach children this “fact” and drive out of their little heads the mistaken intuition that biology is the product of design. It claims that so many people reject evolutionary theory simply because they don’t understand it, and suggests that we should remedy this by attempting to “reach children with the right theory before the wrong one is too firmly in place.”

Contrary to popular belief, many in the Intelligent Design community agree that we should teach evolutionary theory. If it is a theory in play within the scientific community, then it deserves to have a hearing. Even if it stopped being “consensus” science, then we should still teach it as a historical artifact, as astronomers do with the Steady State and Oscillating Universe theories. But if we’re going to teach it, then we should teach the whole thing, warts and all.

The WSJ article is an example of the neglect that the less attractive and convincing aspect of the theory typically gets, either knowingly or unknowingly. When trying to persuade of the truth of evolution many people focus primarily on natural selection. It’s easy to defend and understand. After all, everyone has seen lions take down slow and weak antelope, and horse breeders “select” for speed and stamina all the time. Who would deny the power of natural selection?  Only the ignorant or creationists, right?

Darwin himself subtitled his book on the origin of species: “by means of natural selection.” This is because his own observational experiences most directly related to environmental differences and the variation in species. In his mind, it was tangibly and experimentally valid. The problem is, it was only a part of a holistic theory, and he knew it.  He did not have a concrete proposal for the second half of the theory; he simply presumed its truth and its potency.

The theory of evolution rests upon two pillars: change and selection. There has to be some engine of change on which natural selection can do its work; you cannot select what doesn’t yet exist. Darwin didn’t have this aspect of the theory worked out, but since his time we have discovered DNA and it’s role in shaping organisms. The neo-Darwinian theory incorporates the idea that “change” happens at the genetic level and “selection” happens to the creatures that are carriers of these genes. The reason why this aspect of the theory is downplayed is because of two troublesome facts: the way that DNA is subjected to this change, and the scope of the change necessary to produce any new feature in an organism.

Change to DNA happens by way of mutations. These are corruptions or copy mistakes in the DNA sequence, which either change, delete, or insert nucleotides. The sequence in which nucleotides are arranged defines the makeup of the products (e.g., proteins) that result from the DNA.  The analogy of language has well been used to describe DNA, which would include things like chapters, sentences, and letters. By this analogy, mutations could be said to alter the letters in DNA sentences, or add entirely new ones. Sounds understandable, and workable in theory, but the problem is that the “scientific” theory of evolution requires that these changes be entirely unguided and unpurposeful (read, random). They are errors and corruptions, after all.

In order to build new functionality in an organism you first have to have instructions in the DNA to assemble the necessary parts or to control the expression of existing genes in new ways. Somehow you need to introduce the information (new “sentences,” “paragraphs,” or “chapters”) into the DNA that will be used to drive the biological characteristics that natural selection will preserve or let expire.

Individual genes are painfully long sequences of information — often tens of thousands of nucleotides in length — and few genes work alone (they generally depend upon collections of other genes to do a job). The question is, how does this new information get generated given that the “naturalistic” mechanism implies that it is a random and occasional process? It’s like trying to improve an essay by means of random rearrangements and insertions in the letters of its text. And remember, a change that introduces typos or incoherence will either “kill” the essay or is unlikely to be “selected” for the final draft.

Imagine, then, the evolutionary task of adding an entirely new page to an essay. It is a statistical nightmare, and no wonder that evolution’s defenders shy away from such probabilistic discussions. Assuming you can get a spare page in the essay to work with (say, an accidental copy of another page), and that its mere existence and the evolutionary experiments upon it cause no problem for the essay, then you still have the problem of constructing coherent and well punctuated content that is relevant to the essay and its audience.  And this, also, without doing violence to the existing essay, because, after all, your random “mutations” will not be so kind as to restrict themselves only to your spare page.  If you have 100 pages in your essay, then your chance of getting a change to your target page is 1 in 100 each time a change happens (note that a proper analog to DNA would have the “essay” being hundreds of thousands of pages in length).

Another problem is that any incremental change you make to the essay is not necessarily more likely to have it be preferentially selected or out-compete any other copy of the essay.  It is only when you finally arrive at some improvement to the text that it first has a chance at making a difference.  Mutations are not saved up for later with the goal of finally arriving at “sentences.”  Even if you are lucky enough to get a couple words that might make a difference down the road, the next mutation (in the area of your target sentence) is just as likely to scramble one of those words as to add anything new to them.  Given that genes are many thousands of nucleotides in length, and whose necessary arrangement is rather finicky, then the probability of stumbling upon that new, meaningful sentence is astronomical.

To give you a sense of the probabilities, the possible combinations of any given arrangement of just 100 nucleotides is 1.6 x 1060. One might say, “Sure, but aren’t there a number of different arrangements that could work?” That’s true, there are. It’s like dealing out a random hand of cards and saying, “Wow! What are the odds I’d get these?” The problem is, like in poker, there are only so many hands that are meaningful. Some have tried to quantify this in relation to functional proteins, but I don’t think we even have to.  Here’s why:

There are two ways in which evolution has been required to deal specific poker hands, so to speak. One is in the creation of complementary proteins. As I mentioned earlier, few genes work alone. Genes typically have accompanying regulator proteins as well as the fact that the proteins that genes code for are often part of larger assemblies. This means that at least one of these proteins (which, again, are coded for in the genes) is required to evolve to be complementary to one or more other proteins (like a nut and a bolt). Evolution didn’t just have to do something here, it had to do something specific.

The other way in which evolution has supposedly dealt a royal flush can be seen in what’s called “convergent evolution.” Some creatures share certain genes, but the creatures are so distantly related that their last common ancestor did not even have the gene at that time (or need of it). This means that they must have each separately evolved the same gene. This speaks to the limitations in the number of ways that genes actually have in solving certain functional problems. But more importantly, it means that these creatures succeeded in mutating the DNA to a specific target.

So, then, given that evolution has a target hand that needs to be dealt we can consider the odds. The chances of getting a royal flush of a given suit are about 1 chance in 2.5 million. Not impossible, and this is why some have seen it done. Unfortunately, there are a lot more “cards” needed for a functional gene. A small gene might be around 2000 nucleotides in length, where there are 4 possible nucleotides at any given position. So, the odds of getting any given gene are one chance in 1.3 x 101204. Let’s be really generous, though, and also make sure we have plenty of tries at this.

Let’s start by assuming that only 1/8th of nucleotide positions are really important in the gene (taking it down to 250 now).  Let’s also assume that any two nucleotides are interchangeable. Now the possible combinations are down to 1.8 x 1075. Okay, now let’s assume we’ve got a trillion creatures in our population and they reproduce every year for a hundred million years. Our chances, then, of getting our minimalistic target gene in that period of time are one chance in 1.8 x 1055. That’s 18 with 54 zeros after it! You can add several more zeros to the number of the population, or the offspring per year, or to the time they have to do this, but it’s still a long way until you get even close to powerball jackpot odds. Evolution gives fat chance a full-time job.

In place of the discussion of mutation and probabilities, evolution’s defenders almost invariably appeal to the mystical powers of “environmental pressures.” You see, evolution supposedly happens when it’s needed most. Changing environmental demands cause life to “adapt” or die. New environmental niches open up and beckon life to come and fill them. The problem with this is that it once again directs the focus toward the safer half of the theory.

Environmental changes only serve as constraints and conditions for natural selection. If the climate suddenly turns cold, then members of a species best equipped to handle the changing condition are the ones that survive (or at least out-breed the others). This, however, does not explain where the cold-resistant features of the creatures came from in the first place, such as genes to produce antifreeze glycoproteins{1}.

Unless we’re talking about chemical toxins or radiation (that only yield interesting results in sci-fi) an environmental condition does not cause mutations to happen, much less cause mutations that you particularly need to happen. Mutations happen when they happen, and they are random in every case. Even assuming that it were common to get good mutations, a creature would be just as likely to get a “good” mutation that it didn’t really need (like heat resistance here) as it would be to get one that it could actually use. In fact, it would be even more likely to get a dud, because there are far more ways that a creature could be, but doesn’t need to be, than there are ways that would immediately benefit the creature. Pressing need and inviting ecological niches do not make it any more likely to produce genes than the need for money makes you more likely to win the lottery.

This is the other half of evolution, and these are some of the details and challenges relating to it that you won’t hear in the science classroom or on popular science shows. This is what we should teach: the whole detailed and enigmatic theory. But this is exactly what its proponents do not want to discuss. There is to be no hint of unanswered questions or chinks in the armor of the “indisputable fact” of evolution. To do so would only “give aid and comfort to creationists.” If we are going to teach the theory, then by all means, teach it. But let’s not hide its soft underbelly and pretend that it is an invincible beast.

~~~~~~~~

  1. Notice how this article says that it was “natural selection” that “shaped” unused genes into the antifreeze glycoproteins: http://evolution.berkeley.edu/evolibrary/article/fishtree_06

 

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Posted on May 27, 2014, in Science and tagged , . Bookmark the permalink. Leave a comment.

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