How Many Mutations Are Accumulating Each Generation?

Exactly how many deleterious mutations are accumulating inside humanity each generation? To put this another way, at what rate is the mutational load increasing? How quickly are the deleterious mutations accumulating in our genomes over time, and is this accumulation a danger to our future existence?

Let’s start by stating that mutation rates affect different species differently. Single-celled asexually reproducing organisms tend to have far lower genetic complexity so obviously experience fewer mutations per individual. E. coli has 4.8 million nucleotides while humans have 3 billion. E. coli is a single cell while we have between 50 and 100 trillion cells. Natural selection is also extremely severe in these “simple” species as every single cell is independently subject to natural selection after every single cell division.

Therefore mutations are a much larger problem in sexually reproducing larger species of trillions of cells and billions of reproductive cells which divide many times before reproduction. The potential for something to go wrong rises exponentially with time. In addition, larger sexually reproducing organisms have a greater accumulation of mutations in the male reproductive cells before reproduction, because of their Y chromosome. Mutations double every 16.5 years in human males as they age, resulting in 76% of all mutations coming down through the paternal line.

Many larger animal species have the additional problem of a relatively low population size with a highly complex genome. Humans have a different problem; a large population but a very low reproductive rate. Finally, the larger the species, the smaller overall effect of each individual mutation on the individual and therefore the less likely it is to be removed via natural selection. In these species, including us, the environment and homeostasis will have a far greater influence on reproduction than natural selection.

The Nobel Prize winning grandfather of modern human genetics, Herman Muller  established in 1950 that a mutational load of 0.3 mutations per individual per generation was the limit of human mutational tolerance. The logic was simple. If we have three children per family, we can only afford one of them to carry a large increase in mutational load, and if all carried mutations at this low level they could easily be selected out. However, if all our children had mutational loads above this level then they could not be eliminated from the human race. Mutations would begin to accumulate in a linear fashion over time. Instead of evolving upward, the human race would be on a one way trip to eventual extinction.

In 1971 fellow Nobel Prize winner, Manfred Eigen, also calculated that the maximum number of mutations allowable for evolution to progress as 1/n, or one per genome. Any figure above this would eventually result in genetic “error catastrophe”, a term he coined. For many years geneticists, such as James Crow have continued to worry about the effect of increasing numbers of deleterious mutations are having on the human population, particularly with the trend toward older parenting.

So, how many mutations per person per generation are we actually producing? Is it still within the confines needed for evolutionary theory to work suggested by Muller? Advanced studies on the human genome have now shown us the true figure. Sadly, we now know that the single point mutations (SNV’s) alone, without even counting the many other types of mutations, are accumulating on average at between 75 and 175 in our reproductive cells per person, per generation!

This is a profound discovery with huge ramifications for the future of humanity. Because this astounding fact is foundational to the evolutionary thesis, I have quoted the following admissions from evolutionary geneticists to these mutation rates in humans:

  1. Michael W. Nachman and Susan L. Crowell, Estimate of the Mutation Rate per Nucleotide in Humans.

The average mutation rate was estimated to be approximately 2.5 x 10(-8) mutations per nucleotide site or 175 mutations per diploid genome per generation. The authors find this figure hard to reconcile with evolutionary theory and suggest a mutual cancelling out of mutant nucleotides via epistasis.”

  1. Catarina D. Campbell, Evan E. Eichler, Properties and Rates of Germline Mutations in Humans

Recent genome-wide studies of the SNV mutation rate in humans have started to converge. Studies based on whole-genome sequencing and direct estimates of de novo mutations give an average SNV mutation rate of 1.16 × 10−8 mutations per base pair per generation.”

In plain English this estimate is about 30 new SNV’s per person per generation. Table one of their paper gives a mean mutation rate of 96.3 per person per generation. They go on to say that this is a “lower boundary” estimate and that…

Notably, when considering the total number of mutated base pairs between SNVs and CNVs, CNVs account for the vast majority. CNV’s being copy and deletion mutations covering large number of nucleotides. Put together these two sources of mutations represent hundreds of new mutations per generation.”

  1. Neel JV, Satoh C, Goriki K, Fujita M, Takahashi N, Asakawa J, Hazama R, The Rate With Which Spontaneous Mutation Alters the Electrophoretic Mobility of Polypeptides.

The implication, if these exon rates can be generalized, is of approximately equal to 20 nucleotide mutations per gamete per generation. This estimate of the frequency of point mutations does not include small duplications, rearrangements, or deletions resulting from unequal crossing-over, transcription errors, etc.”

  1. Ellie Dolgin, Nature The Real Mutation Rate Revealed, August 29, 2009

 “Every time human DNA is passed from one generation to the next it accumulates 100–200 new mutations, according to a DNA-sequencing analysis of the Y chromosome.”

Confessions do not come clearer than that, and from the pens of the worlds leading human population geneticists. We are clearly generating an abundance of deleterious mutations, and practically zero beneficial mutations. This has profound implications for anyone who has built their worldview on the assumption that evolutionary theory has slam-dunked all opposing theories of our origins.

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