When Positive Selection Is Negative for Health

A paper touts “positive selection”
repeatedly but really is about
degradation and genetic disease

Remember when we showed the different kinds of “natural selection” discussed by Darwinists, and showed that only “positive selection” matters for upward, progressive evolution? (2 Sept 2019). What if an evolutionist tried to argue that positive selection is like rusting iron on a bicycle, or holes in a hot air balloon making it lose altitude, or walking up a down escalator, descending faster than you can ascend? Yet that is like what a new paper calls “positive selection.” Some evolution! Life will go extinct with that kind of Darwinism.

Sperm sequencing reveals extensive positive selection in the male germline (Neville et al, Nature, 8 Oct 2025). To be fair, this paper is not trying to argue that life is getting progessively better over time, or that men are getting stronger and fitter and healthier because of Darwinian evolution. It’s only showing that sperm cells accumulate damaging mutations more slowly than body cells do.

We sequenced sperm and blood from healthy men spanning a wide age range to quantify mutation rates and positive selection in the male germline. Mutation rates and signatures in sperm matched those from family trio and testis studies. Despite sharing SBS1 and SBS5 signatures, mutations accumulated around eightfold more slowly in sperm than blood, a result that supports our previous observations of the protected nature of the germline relative to the soma.

One might think this provides evidence of intelligent design: the male reproductive organs contain mechanisms like DNA repair that locate damaging mutations and fix them. Body (soma) cells accumulate mutations that lead to aging and cancer, but mutations that damage sperm and egg cells are especially harmful because they carry the damage into the next generation. Driver mutations are those that drive the development of cancer and other diseases. The authors mention that mutation-damaged sperm cells can result from the lack healthy DNA repair systems:

We next examined whether risk factors beyond age contribute to the accumulation of disease or driver mutations in sperm. Known germline mutagens include chemotherapy, inherited DNA repair defects and weaker influences from genetic ancestry and smoking.

Thank God for Repair Machines

Obviously, DNA repair systems, which are well known to work in healthy cells, are good to have around. When the repairman is sick, bad things can happen! Mutations, like broken car parts, can’t be fixed. But instead of praising God that He created repair systems for our DNA, these authors carry on and on about “positive selection,” mentioning it 83 times. Selection is Darwin’s keyword from the Origin of Species. It implies that all of life has progressed from simple to complex by blind, unguided natural processes (i.e., chance: the Stuff Happens Law). You will not find anything resembling evolutionary progress in this paper.

The repetition of “positive selection” gives the misleading impression that something positive, good, or progressive is occurring in the human genome. Far from it: if anything, the human reproductive system still contains working mechanisms to eliminate harmful mutations as much as possible (in this case, eight times more effective than in somatic cells). The authors could have said, “Thank God that even in this sinful, cursed world exposed to damaging radiation and carcinogens all around, many humans can still be born and live fairly long and healthy lives.” But no: they have to use Darwin’s favorite word selection to account for the fact that we are not extinct yet. Yes, genetic disease is a serious problem. But watch sports and Olympic games to appreciate the fact that even after thousands of years of mutations, and hundreds of generations, exceptional physical feats are still possible, thanks to highly sophisticated maintenance and repair systems built into our cells.

Sanford’s book examines the impact of near-neutral mutations that are invisible to selection.

Even with DNA repair, though, about 100 new mutations get passed on to the offspring each generation. The human genome is not progressing by Darwinian evolution! It is degrading over time due to Genetic Entropy.

How Is Positive Selection Measured?

The measure that Darwinists use for “positive selection” is the dN/dS ratio. We’ve shown before that this metric, as mathematically precise as it looks, has nothing to do with health or progress (see “Positive Selection Is a Myth,” 22 May 2020). It only refers to nucleotide changes in DNA that have not been weeded out: i.e., they did not cause death. The authors admit, however, that determining instances of “positive selection” cannot be known for certain. Watch the word “likely”—

Mutations in sperm that are likely disease-causing and those classified as known driver mutations represented overlapping, yet distinct, annotations (Fig. 3a). Across the cohort, an estimated 3.3% of sperm carried a likely disease-causing mutation. Of this, approximately one-third (1.2%) was expected by the neutral mutation model, another third (1.1%) was explained by known driver mutations and the remaining third (1.0%) was unexplained by either source. These findings indicate that the increase in likely disease-causing mutations is largely driven by germline positive selection on known genes, but also indicate that additional driver genes with disease associations remain to be identified.

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Another built-in protection from transmission of harmful mutations in reproduction comes from the “facts of life” about sperm and egg cells. Only one egg is normally implanted at a time, but sperm swimming toward that egg number in the millions. If only about 3.3% of them carry a disease-causing mutation, chances are very high that bad ones will be swamped by healthy sperm. Diseased sperm cells may not even be healthy enough to make the journey.

Fortunately, women have additional protections against transmitting disease-carrying mutations, even though all their egg cells are all made during gestation (see Live Science, 13 Aug 2025). With these protections operating in both sexes, the number of genetic diseases transmitted to offspring is strongly reduced. Notice again, though, that none of these “facts of life” suggest that humans are evolving upward into fitter beings with novel features.

Be not deceived: This paper is not about progressive evolution. The dozens of mentions of “positive selection” are misleading and should be dropped because of the Darwinian implications. It’s really about prevention of mutational burden— a phrase the authors mention almost as frequently as selection. If anyone points to this paper as proof of evolution happening today in the human race, now you have the information to turn it around. A pithy metaphor might help: “If a down escalator is moving faster than a man trying to walk up it, is he making progress?”