Genetic EntropyMay 15, 2007
I hope you’ve read all the articles so far because I’m taking it up another notch. If you haven’t already I suggest reading the short article on Facts and Meanings as well as the ground work set down in the introduction section. Genetic Entropy was really the one concept that got me to really start looking into things, and it was one of my primary reasons for starting the site.
This article is basically a summary of a book called “Genetic Entropy and the Mystery of the Genome” written by Dr. John C. Sanford. I have to warn you that I was utterly devastated after reading this book. It utterly crushed my view of the future of humanity and the world. If you are having a bad day or have something important to do soon, I would suggest you stop reading and come back at a later time. Emotions aside, we have made some very important discoveries in genetics that really deserve attention and consideration. Dr. Sanford has posed the question “Why don’t we see this in the news headlines?” the answer is that the truth can be uncomfortable.
To give you some context, let’s start off by looking at what has been called the Primary Axiom of Neo-Darwinian Theory. No matter what the specific models or ancestry that are given, the underpinning idea of Neo-Darwinian Theory is that mutation and natural selection combine to cause evolutionary progress. This is how we went from single celled organisms to the dominant species on the planet. Mutation and natural selection can be thought of as a balance. Mutation adds in random variations in the genetic code and natural selection is simply the process by which more fit, healthy organisms are more likely to produce. By itself, natural selection cannot create any new variation, it only eliminates variation. If you are sickly, or have a lethal mutation, natural selection says you will probably not pass your genes on to the next generation. In this view, evolution depends on balance between chaos (mutations) and static order (natural selection).
So what happens if things are out of balance? If natural selection is too strong, or if mutations are practically non-existent then evolution grinds to a halt. There is no new variation, and what varieties do exist would be whittled down to the most “optimum” until you have a basically homogeneous population. If, on the other hand, mutation is too high or natural selection stops (like small populations) then bad mutations start piling up and the species degrades. This is called Muller’s Ratchet which eventually leads to Mutational Meltdown. It is something that we have observed in endangered species and a problem that threatens all species with small or in-bred populations.
Now that you have some context let me explain two other key points. First off, good mutations are exceedingly rare. They are so rare in fact, that it is hard to get an exact number on how rare they are. In comparison to nearly neutral and bad mutations a fair number is in the order of 1 in a million (1,000,000) mutations actually being beneficial. That means that in general we can consider mutations bad and natural selection must eliminate virtually all mutations.
The second item is what is commonly referred to as Junk DNA. Junk DNA is simply the name that we assign to portions of DNA for which we do not know their function. Originally it was said that about 98.5% of our entire genome was junk DNA. What this translates to is that for 98.5% of the genome we have no idea what it does. Specifically, the assumption was that all functional DNA should encode for proteins so anything that doesn’t encode for a protein must not do anything. Recent research has shown that this assumption is wrong because we have discovered sequences that act as regulatory mechanisms for protein production and respond to the cellular environment. Regulatory sections shrink our supposed 98.5% junk. No one is entirely certain at this point how much of our genome is functional, at this point a big question mark still floats over much of the genome. The important thing to note is that as our knowledge of genetics progresses the amount that is labeled as “junk” is gradually shrinking.
Human Mutation Rate
So given all this information, scientists have been very interested in finding out exactly what the human mutation rate is. The global average of birth rate is 3 children for every 2 people. So if natural selection were laser accurate that would mean that it could hold ground, with no evolutionary progress, with a mutation rate of 1 mutation in every 3 people. This would be just low enough that we could maintain our population at a steady rate, there would be no room for population growth or evolution. A high mutation rate in normal models would be around .1 or 1 in every ten individuals. As the mutation rate gets higher it necessitates a higher birth rate to maintain a population. In a simple model, the necessary birth rate dependent on the mutation is x = 2/(1-m). So with a mutation rate of .5 half of all people would be mutant and thus we would need a birth rate of 4 children per woman to maintain a population that was not accumulating mutations. As this number approaches 1 mutation per person (that’s everyone) you can no longer select any individual who does not have a mutation, even with perfect accuracy in natural selection. Mutations rates with multiple mutations per person necessarily lead to a growing number of mutations, which in experience, leads to reduced fitness and eventual species extinction over long periods of time.
In 2000, Dr. Crowell, from the University of Arizona Department of Ecology and Evolutionary Biology, published a paper estimating the human mutation rate at around 175 mutations per person per generation. Kondrashov, from the National Center for Biotechnology Information, published a paper in 2002 estimating the rate of point substitution mutations alone at 100 per person per generation. This high mutation rate is commonly accepted in the scientific community today. Kondrashov’s numbers only include point mutations. They do not include numbers for deletions, insertions, duplications, translocations, inversions, macro-mutations and mitochondrial mutations. There are also sections of DNA called microsatellite regions that have mutation rates easily 1,000 times higher. The true human mutation rate has not been measured exactly – it could easily be in the thousands – and we can observe that it far exceeds comfortable numbers like 1 in 10 individuals.
It would appear mutations happen faster than natural selection can keep up with. Our scale is unbalanced; we are not evolving, but degenerating. What are the implications of this? It means that every generation that is born has 100 more mutations than the generation before it. We are all highly mutant, and not in an X-men kind of way. We judge what is ‘normal’ off of each other. So that means that anything that affects the entire species is considered normal. How many of us have bad vision, allergies, mangled toes, lopsided ears, joint pains, skin spots, jaw pops, back problems, heart problems, and let’s not forget cancer… We are all unhealthy, unfit in one way or another, and it’s sad to admit it, but that is the current state of life. We’ve … Got … Problems. Genetic entropy is all around us, it is so ubiquitous that we don’t even notice it anymore. Blinding Light. The explanatory power of genetic entropy is comprehensive.
Nearly Neutral Mutations
So far we’ve assumed that natural selection is laser accurate, that would allow it to select away one mutation per generation. But Natural Selection operates at the organism level and mutation happens at the molecular level. Let that one sit for a moment. Natural selection is on the level of organisms feeling attracted to one another and mating. Mutation is within a stone’s throw of the small units of existence that we know about. As you read this, 10^24 atoms of your car just turned to rust. Are you going to buy a new car now?
Most mutations are nearly neutral, not entirely neutral but their effects are subtle enough that they are hard to select against, which makes the problem worse. You have a library inside you that is 6 billion letters long. If I go past rows of books, pull out a giant ladder, climb to the top and pull out a book, then I open that book and change one letter, does that matter to the library? Not really. Does that make it entirely neutral? There is an important difference between near-zero and definitely zero importance. If I go in and make 100 typos in the library everyday for a thousand generations you will start noticing a decline in your library user review (fitness). Can this problem be solved by throwing out entire libraries to fix typos? Not really. This problem has been recognized by evolutionary geneticist Kondrashov in his paper Why Have we not died 100 times over?, often called Kondrashov’s Question.
Consider your own family history, did your parent’s quirks keep them from reproducing? How many quirks can go unnoticed entirely until they are passed on to the next generation. Since I can’t speak for your family I’ll give you a couple examples in my own family. My grandfather was 6′ 4″ and died of an enlarged heart when he was 40. My mother has a not so neutral problem with scoliosis (deformation of the spine) that was passed down to all of her sisters. Thanks to corrective surgery you could never tell today. Having back problems didn’t keep her from having kids, a fact I’m grateful for, but there’s a risk it could get passed on to the next generation, maybe silently. “The fact that the spine and spinal column ever form correctly is amazing given the complexity of the process from an embryological standpoint” (iScoliosis). “The gene that causes scoliosis remains undiscovered”.
I myself have a deviated septum that not even my wife mentioned until after we married. “It’s called tact, you don’t mention other people’s deformities,” according to my wife. In evolutionary terms traits not under selection can drift to fixation (everyone has it). “Estimates are that 80 percent of all nasal septums are off-center, a condition that is generally not noticed.” I also have allergies, some of which I got from my dad, some of which are new that I can pass on to any children I have.
So does this mean we should not have kids? Certainly not. Life is full of risk, and the reason we get up everyday is because somehow we believe that the risk is worth it. Allergies and bent noses don’t make life not worth living, it just means that we should have a healthy respect of our own mortality. We are finite creatures and no matter how cool you are, we all eventually succumb to the entropy of our own bodies. It’s what we do with our time that matters.
In retrospect, this idea really shouldn’t be that shocking. Entropy is a law of nature and everything that we see around us is dying, decaying or falling apart. I have never seen a single thing in all my life that is immune to entropy, it affects everything. My 40 year old apartment naturally degrades, the road outside must be constantly patched, every human ever born eventually dies, and the sun itself will eventually die out.
For more Info
If you would like a more in-depth discussion on Genetic Entropy I would seriously recommend getting the book. This article barely covers up to chapter three. Dr. Sanford addresses every imaginable objection in his book in enough detail that it has (maybe unfortunately) silenced every intellectual criticism so far. In particular, he covers the challenges with natural selection in much more detail than I have. He discusses problems with proposed solutions in Natural Selection, Artificial Selection (Eugenics), problems with noise, cloning, evolving genes, Crow’s solution, macro-beneficial mutations, and historical evidence. He also answers questions like how many mutations can be selected against simultaneously, and other possible objections. If you are a super-poor college student and you are interested in looking into this I will buy you a copy. This isn’t a book promo, this is real life, and I think this is important to know.
(Contrary to the idea that all humans preceding us were ‘primitives’ there is a fair amount of evidence to suggest that our ancestors were more genetically fit in the past. Can you think of any “myths” with long lived, smart, technologically advanced people in them? I’ll be looking at a couple in future articles.)