About Michael Lynch and article Rate, molecular spectrum, and consequences of human mutation

How did you respond to the results of this article? (I am not a creationist or a TDist)

Rate, molecular spectrum, and consequences of human mutation (https://www.pnas.org/content/107/3/961)

Thus, the preceding observations paint a rather stark picture. At least in highly industrialized societies, the impact of deleterious mutations is accumulating on a time scale that is approximately the same as that for scenarios associated with global warming—perhaps not of great concern over a span of one or two generations, but with very considerable consequences on time scales of tens of generations. Without a reduction in the germline transmission of deleterious mutations, the mean phenotypes of the residents of industrialized nations are likely to be rather different in just two or three centuries, with significant incapacitation at the morphological, physiological, and neurobiological levels. Ironically, the genetic future of mankind may reside predominantly in the gene pools of the least industrialized segments of society. Possible solutions to this problem, including multigenerational cryogenic storage and utilization of gametes and/or embryos, will raise significant ethical conflicts between short-term and long-term considerations.

That Michael Lynch is correctly pointing out that advances in medicine, technology, agriculture, and so on, is a large part of the equation that explains why humans in industrialized nations have come under a larger mutational load.

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Ok Ok Thanks :smiley:

My concern is the use of this article by creationists.

Lynch followed up that 2009 paper with this one in 2016. It is certainly a bleak thesis, complete with melting brains.

What is exceptional about humans is the recent detachment from the challenges of the natural environment and the ability to modify phenotypic traits in ways that mitigate the fitness effects of mutations, e.g. , precision and personalized medicine. This results in a relaxation of selection against mildly deleterious mutations, including those magnifying the mutation rate itself. The long-term consequence of such effects is an expected genetic deterioration in the baseline human condition, potentially measurable on the timescale of a few generations in westernized societies, and because the brain is a particularly large mutational target, this is of particular concern.

So all things being equal, as @Rumraket has pointed out, relaxed selection would be expected to result in an increase in genetic liabilities which would have otherwise been culled. This would be true given a baseline mutation rate which is not perturbed. What commands more attention is that, as Lynch goes on to discuss, all things are not equal. He goes on to discuss the aggravating role of environmental mutagens.

Large scale social trends also tilt the scale. Age of childbearing and family size comes into the picture…

…it is clear that the per-generation mutation rate is not a constant. Most notably, the mutation rate per generation increases by a factor of 2 between males of age 20 and 40 years…

…another aspect of modern human behavior—the tendency toward families of similar size (the two-child syndrome in middle-class neighborhoods in westernized societies)—may thwart this aspect of selection as well. Notably, this very strategy (equilibration of family sizes) has been used to accumulate deleterious mutations in experimental populations of Drosophila , yielding a 0.2–2% decline in fitness per generation

The wondrous improvements in medical care we have experienced in the past century might be another example of no free lunch. I’m aware there are counter arguments, but the contention Lynch makes here is consistent with the rather dramatic fall in sperm count, motility, and quality which has been observed, and poor sperm quality has been linked to subsequent childhood mortality and genetic problems.

None of this lends any support to genetic entropy, but relaxed selection, environmental, and social factors might indeed be conspiring to present a rather pervasive challenge.

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Articles say that there are 100 to 200 new mutations per individual in each generation (Nachman and Crowell, 2000; Dolgin, 2009; Lynch, 2010). Creationists are using this against evolution, how to refute them?

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It’s probably more like 75 new mutations per generation, but whatever. How to refute them depends on what argument they’re making.

They say that 100 new mutations appear in the human genome, a result of genetic entropy.

That’s not what GE says.