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In the book Genetic Entropy & the Mystery of the Genome the author says that the genome cannot be old because the genome is "decaying". Decay is a very subjective term, but in this case he means that the fitness of humans is going down not up. Is it true that our genome is decaying over time, and that the fitness of humans is decreasing? Here is a quote from the book, that might explain his argument:

Kondrashov, an evolutionist who is an expert on this subject, has advised me that virtually all the human geneticists he knows agree that man is degenerating genetically. The most definitive findings were published in 2010 in the Proceedings of the National Academy of Science by Lynch.4 That paper indicates human fitness is declining at 3–5% per generation.There is really no debate on current human genetic degeneration.

Perhaps this more shines more enlightenment in my question. This idea of human fitness going "down" is my main concern. Essentially, in his book he claims that because we are going "down" (meaning fitness is declining) not "up" (whatever that means) our genome must therefore be young. If I understand the issue correctly, mutations "create new information" by creating different proteins or leading to an abnormal protein products. However, I thought that the force of natural selection should be strong enough to get a rid of those genes that are so and so responsible for our fitness declining.

Sanford, John C., and John R. Baumgardner. Genetic Entropy & the Mystery of the Genome. Waterloo, NY: FMS Publications, 2008. Print.

Feel free to point me to similar questions that may been helpful or are similar to this one.

fileunderwater
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Lucian09474
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    You need to be more specific with what you are referring to with the "the genome is decaying" statement. "Decay" is also a very subjective/value-laden description of a genetic process, and you should specify exactly what process you are interested in. Is it just "random mutations" -> "genetic dissimilarity over time" (~genetic distance), or something else? At the moment, it is really hard to understand exactly what you are asking about, and therefore hard to formulate a relevant answer. – fileunderwater Aug 10 '15 at 13:36
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    @Lucian - I suggest you edit this as much as needed to make it acceptable as a clear question, or let someone else do this for you. You won't get your question answered if you get it closed first. Avoid personal claims like, "I have read extensively on evolutionary biology." You may well have read a few books, but if the books are written from a Creationist point of view, you have not read extensively. That's a bit like claiming you've read a lot about astrophysics because you've read every one of Ken Ham's books. A good answer follows from a good question. Help us to help you. – anongoodnurse Aug 10 '15 at 16:34
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    I think this question has been completely changed, to the point that neither of the answers to it make any sense. – March Ho Aug 11 '15 at 08:29
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    @MarchHo I still think the core aspects of your answer is relevant though, to the last part of the question (you might need to reframe it a bit though). – fileunderwater Aug 11 '15 at 10:16
  • The question makes more sense now, I removed my down vote. Good job for improving over your original post! – Remi.b Aug 11 '15 at 15:05
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    The book you quote is not peer-reviewed; assertions like these are not scientific, they are just the author's opinions: "Kondrashov, an evolutionist who is an expert on this subject, has advised me that virtually all the human geneticists he knows agree that man is degenerating genetically." I would encourage you to distinguish between replicable observations ("facts") vs. rumors, anecdotes, and hearsay. – mdperry Aug 11 '15 at 16:43
  • @mdperry As the OP mentioned, they are not familiar with the discipline of evolutionary biology. Therefore it is not justified on out part to expect them to discern between a bad reference and good ones. We should point the right references to them. The question is clear now and is on-topic. – WYSIWYG Aug 11 '15 at 16:57
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    @WYSIWYG Did you ever consider that this OP could be trolling? Cutting and pasting excerpts from a creationist for one's Biology SE posts could be considered inflammatory. If the OP is genuinely curious then helping them to evaluate the literature in a field, and pointing out weak vs. strong arguments is demonstrating the epistemology of the scientific approach. If we just spoon feed them I fear we will end up with a generation of scientists who rely on others instead of reasoning answers for themselves. – mdperry Aug 11 '15 at 21:32
  • @mdperry I apologize if that was ever the image I projected. I was advised to not use personal statements like "Ive read about evo bio", I am no evolutionary biologist. I am a double major in geology and chemistry with interest in planetary science. I am very interested in knowing the mechanism by which the non living chemicals formed the first living thing. I am not an evolutionary biology, in my original question i've stated the reason why I wanted to know, but I removed it. I felt that I was being lied to when this was brought up from creationist all the time. – Lucian09474 Aug 12 '15 at 04:20
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    This question is also addressed in this post. You can have a look there, too. – WYSIWYG Aug 12 '15 at 10:28
  • @WYSIWYG yes someone earlier pointed out to a very similar question. I managed to get answers to questions that I did not even know how to ask yet. – Lucian09474 Aug 13 '15 at 19:02

4 Answers4

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If I understand the question correctly, you are asking why random mutations (most of the non-silent ones are deleterious) cannot create information and improve the overall fitness of the organism.

This is a common creationist statement, and has been shown to be incorrect in many different ways. The best way this can be shown to be false is by simply applying natural selection.

E. coli has a beneficial mutation rate of $10^{-5}$ per genome-generation (source) and a detrimental mutation rate of $2×10^{-4}$ per genome-generation (source).

Therefore, at first glance, the claim that the "genome is deteriorating" appears plausible. However, natural selection quickly acts on these mutants with deleterious mutations due to their low fitness. Therefore, the deleterious mutations are removed from the gene pool and are replaced with their beneficial counterparts instead.

If we define "information" as beneficial adaptations to the environment, random mutations themselves do not directly create the information. It is the application of natural selection that allows the fitness of the organism to increase despite the presence of random mutations.

March Ho
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  • I have two concerns with this answer: 1) How did you do to infer that the OP was interested in the ratio of beneficial over deleterious mutations? 2) you said random mutations themselves do not directly create the information. I can see you are trying to use the OP's words (which is great in general) but it end up sounding quite weird. Definitely, mutations create genetic variance (and therefore increase information or decrease Shannon entropy) while directional selection reduces genetic variance (decrease information). – Remi.b Aug 10 '15 at 15:52
  • Of course, it is the combined effect of those two things that allow for adaptation. It is also wrong to say atural selection that allows the fitness of the organism to increase despite the presence of random mutations as it seems like mutations are bad and NS is good which is wrong. – Remi.b Aug 10 '15 at 15:52
  • @Remi.b - Selective pressure is shown to select out the beneficial mutations. That's how evolution works. – anongoodnurse Aug 10 '15 at 16:24
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    I am well aware of the basics of evolutionary biology. Mutations increase genetic variance (and therefore shannon's definition of information) by introducing new variants in the population. Natural selection decreases genetic variance (by selecting out deleterious variants) and it therefore decreases information. This is the very basics of evolutionary biology. The term "information" seems to be slightly loaded as being "a good thing" but under the standard mathematical definition the above answer is partially wrong – Remi.b Aug 10 '15 at 17:13
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    I agree with @Remi.b Information content is basically a log likelihood function of the entropy. MarchHo, I think you mean information in the sense of functional repertoire of genes, but such a terminology may be misleading. You should clarify it. – WYSIWYG Aug 10 '15 at 18:10
  • The book in question is more of an informational pamphlet than a scholarly monograph. The sort of thing that you might find someone handing out on a street corner. The sophistication of composition is at about the second year UG level. The problem I have with this post is that the term "Genetic Entropy" has no clear sense, and may mean different things to different people. The notion seems to approximate: "The Shannon-entropy of the human genomic sequence". Shannon-entropy measures information content in bits, in contrast to thermodynamic entropy which uses energy units to measure disorder. – RosieF Aug 10 '15 at 18:49
  • @Remi.b should I delete this question?, I thought it was silly to ask the question we are having discussion about this and I had no way of defending natural selection, as like I stated I am only familiar with genomic research. In the book a lot of analogies are used to make the reader understand. the author is a 25+ year Cornell University professor, so he is not just some guy. The argument he poses is used very commonly from creationist I come around ( I am heavily surrounded by creationist views) and really it is an eye opener to me how passionate creationist are about "debunking evolution" – Lucian09474 Aug 10 '15 at 22:02
  • Well, the question is unclear (I hope I managed to make clear why this is the case in my now deleted answer/comment). The question ended up being closed as unclear. You can delete if you want but you don't need to as it is closed anyway. However, as you checked @MarchHo's answer, it seems like he managed to give you a helpful answer (and so other might see something helpful in MarchHo's answer). So maybe just keep it like this. I am just hoping that the error/misleading information in the last paragraph will be corrected by March Ho. Thank you Lucian09474 – Remi.b Aug 10 '15 at 22:13
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    @Remi.b You make a good point on defining information in terms of Shannon entropy, I think I have a misconception here, will update the question once I figure out what is wrong. – March Ho Aug 10 '15 at 23:09
  • @Lucian09474 You cannot delete posts with upvoted answers. The question is okay if you clarify it. It is fine if you do not know a certain concept and ask a question about it. However, your question should be specific and should have a clear statement. – WYSIWYG Aug 11 '15 at 05:09
  • @Remi.b I think the answer makes sense if "information" is not defined in the sense of Shannon entropy, since the "information" as defined by the question clearly has nothing to do with it. – March Ho Aug 11 '15 at 08:01
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    To my knowledge there is no other commonly accepted definition of information than the one suggested by Shannon. I don't mind using another definition but the definition should then be written down (which is currently not the case neither in the question nor in your answer). – Remi.b Aug 11 '15 at 15:03
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    Kolmogorov information is also commonly used - most kinds of mutations other than substitutions (such as duplications, be they internal tandem or whole-gene or genome) automatically increase the Kolmogorov information content because the strings that represent genome sequences have to be made of more bits to describe them.

    Any mutation also increases the Kolmogorov information content of the gene pool.

     – Ankur Chakravarthy Sep 03 '15 at 14:46
  • The book makes the argument that the human population with access to modern medicines is at a point where natural selection is less fierce and allows carrying more of the deleterious genes into the next generation than ever before. This argument cannot be countered by referencing E.coli, since we are in a different evolutionary situation. I completely disagree with the findings of the book, but this answer does not provide a satisfying retort for me. – James May 15 '17 at 02:44
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Regarding the reference to Lynch, actually reading this paper is illuminating (http://www.pnas.org/content/107/3/961.full). What Lynch is saying with regards to degeneration is that he and others feel that modern technological advances may relax selection pressures, thus allowing the survival and reproduction of many who would otherwise be selected against, increasing the rate of mildly deleterious mutations in the human population.

Sandford willfully misreads this in order to inject his creationist/intelligent design mythology (Man's creation by god, the fall, no evolution, but rather decay from god's perfection, etc). However, this is definitively NOT what Lynch and other biologists are suggesting. Decay is a loaded word. The genome is constantly changing from generation to generation on an individual basis. Selection simply eliminates overtly deleterious mutations.

Lynch is suggesting a sort-of technological doomsday, where human success at subverting selection ultimately lead to an unsustainable mutational burden and the collapse/extinct of humanity. Differences in selection pressure affect what genomes are propagated onward. Previously deleterious mutations that can be survived in our current environment are seen some malign decay, but this is how selection works. As the environment changes (including technological changes), selection pressures changes. If selection pressures revert, such persons will once again be selected against. An overly dramatic shift in selection pressure (such as collapse of society, or other forms of massive environmental change) could indeed kill us off, but this is true of any species and is in no way unique to humans.

InactionPotential
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  • Are you suggesting that Prof. Sandford's assertion, quoted above "There is really no debate on current human genetic degeneration." is not actually supported by the reference that he cites? – RosieF Aug 11 '15 at 19:52
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    Well, I think he's being intentionally misleading, especially in his word choice. This is probably related to a typical (sometimes intentional) creationist misunderstanding of evolutionary processes. If there were some ideal human genome, then most mutations, increasing our divergence from this ideal, could reasonably be seen as degeneration.

    Evolutionarily speaking, there is no ideal genome, only those that are more or less well-suited to their current environment. He's postulating a non-existent absolute where there are only relative differences.

     – InactionPotential Aug 11 '15 at 20:41
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A small addition to what March Ho has mentioned in their answer.

Fitness is not absolute; it is dependent on the present environment. Fitness has no meaning when the selection factor is not defined.

You can consider a commonplace example: Can you, by just looking at an individual say how fit they are (of course I am not talking about those who are clearly ill, obese or malnutritioned)? Unless you assess their performance in a task you cannot really say how fit they are. Same goes with evolution.

Now consider another hypothetical example. You would be aware of the fact that the sickle cell trait (mutant haemoglobin) provides immunity against malaria. If your task is some kind of physical exercise then obviously the sickle cell trait is deleterious. However, if there is a malaria pandemic then the sickle cell trait would provide a great survival advantage and therefore these individuals would be deemed fit under these conditions.

It is to be understood that evolution does not work towards "improvisation" of species. Just because we assume that a certain trait is advantageous for an organism, it is not necessary that it would evolve. Have a look at this post.

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WYSIWYG
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  • Also, as a deleterious allele spreads through the population, it can eliminate carriers from the population at an increased rate, meaning that non-carriers have an advantage and the mean fitness of the population consequently goes up. Sanford's main flaw is the treatment of relative fitness as absolute.

    Also, the whole mutational meltdown from decay stuff is only a problem in small populations, where deleterious alleles can be fixed that much more rapidly. To extrapolate this to organisms with large population sizes or to hold it as a general truth of evolution is iffy.

     – Ankur Chakravarthy Sep 03 '15 at 15:12
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Well, you've already mentioned Alexei Kondrashov. Here's his talk (in russian unfortunately): http://www.youtube.com/watch?v=YsgO8JTN7KE

To summarize it:

Yes, that decay is happening and at a pretty catastrophic rate. As of 2012, he estimated the rate of IQ decay (and fitness decay is somewhere close) to be within the range of 1% and 10% per generation. The former is ok according to him, cause "in 100 generations we'll surely be swept away by a nuclear war between big-endians and little-endians". The latter will be unfortunate, cause in 10 generations we'll "fall prey to our own stupidity". He speaks of stupidity because our brain is the most transcriptionally complex structure in our organism, thus it suffers from genetic damage sooner than anything else.

(It's worth noting here that AFAIK, one of Kondrashov's children has Down syndrome; another one, Fedor, is a remarkable geneticist as well, focused on epistasis.)

Those estimations are supported by the following molecular data: no matter the age of the mother, she gives 15 new single-nucleotide mutations on average to her offspring. Father gives about 10 mutations per each year of his life after reaching puberty, historically 70 on average. Out of those mutations most are neutral or silent (due to genetic code degeneracy), but on average ~1 out of 70 leads to a change in aminoacid sequence of some protein, usually harmful.

Here are 2 papers: decay of cognitive indicators of children with parent's age: http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1000040

Another link from Kondrashov: drosophila simulation of middle-class neighborhood (MCN) population, where each family has exactly 2 children, son and daughter, and no natural selection pressure is applied: such population rapidly deteriorates with fitness in wilderness decreasing by 2% per generation: http://www.ncbi.nlm.nih.gov/pubmed/9371795. Kondrashov says that after several generations you can hear the difference between MCN drosophila and wild-type - wild-type is much more noisy and active.

He also mentions that frequency of autism, diagnosed in the US has increased 5-fold since 1950.

Boris Burkov
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  • It appears to me you are using a nonstandard definition of fitness. Fitness is simply the expected number of offspring, given a genotype, for a carrier with that genotype. Cognitive indicators et cetera don't necessarily correlate with the ability to reproduce, and unless they did there are no real implications for fitness. – Ankur Chakravarthy Sep 03 '15 at 15:07
  • @AnkurChakravarthy True. In fact, I'm mixing here the data about IQ and about fitness. They say that average non-silent aminoacid substitution in a protein decreases fitness (expected # of children) of organism by 1%, so 2-3% per generation, when fathers are ~30 year old on average seems to be a correct estimation. – Boris Burkov Sep 03 '15 at 16:49