Much thanks to redditor “JoeCoder” for compiling the following information on genetic entropy.
At the crux of the debate is whether evolution makes us better (rise from apes) or worse (the fall) over time. But it turns out that Humans (and likely many other animals) are degenerating much faster than beneficial mutations appear and become fixated.
- “Our numerical simulations consistently show that deleterious mutations accumulate linearly across a large portion of the relevant parameter space. This appears to be primarily due to the predominance of nearly-neutral mutations. The problem of mutation accumulation becomes severe when mutation rates are high. Numerical simulations strongly support earlier theoretical and mathematical studies indicating that human mutation accumulation is a serious concern. Our simulations indicate that reduction of mutation rate is the most effective means for addressing this problem. … However, over long periods of time, even with intense selection, a significant number of deleterious mutations consistently become fixed. … Intensified natural selection only marginally slows the accumulation of deleterious mutations.”, Using computer Simulation to Understand Mutation Accumulation Dynamics and Genetic Load, Computational Science, 2007
This problem is acknowledged in peer-reviewed literature. Geneticists call it a serious concern10, a paradox11, asking “why aren’t we extinct?”18, “why have we not died 100 times over?”12, stating that we’re genetically inferior to our stone-age ancestors14, and suggesting “multigenerational cryogenic storage and utilization of gametes and/or embryos”13 to preserve our genome. Many (but not all) from this list limit human degeneration to the last hundreds or thousands of years due to decreased selection, but stop short of calculating any way that deleterious mutations can be removed faster than they accumulate. Simulations show even strong selection isn’t enough.10.
- Using conservative calculations of the proportion of the genome subject to purifying selection, we estimate that the genomic deleterious mutation rate (U) is at least 3. … The reduction in fitness (i.e., the genetic load) due to deleterious mutations with multiplicative effects is given by 1 – e-U. For U = 3, the average fitness is reduced to 0.05, or put differently, each female would need to produce 40 offspring for 2 to survive and maintain the population at constant size. This assumes that all mortality is due to selection and so the actual number of offspring required to maintain a constant population size is probably much higher.Estimate of the Mutation Rate per Nucleotide in Humans, Genetics, Sep 2000
CONCLUSION: If thousands of deleterious mutations accumulate on the path to a beneficial one, even in the fittest members under strong selection, how was the genome produced in the first place?
Here is a link to JoeCoder’s list of sources referenced above.
The scientific community asks “why have we not died out 100 times over”. I think the answer is simple. We haven’t been around as long as you think! But we are degrading. See my post on de-evolution and the 7000 year theory.