Why Mutation Hot Spots Are Lethal to Evolution

Mutational hotspots pose a major problem
for evolutionary models, and this issue is far
 more complex than previously believed

By Jerry Bergman, PhD

Mutation Hotspots and the Myth of Random Change

One reason why “from-goo-to-you-by-way-of-the-zoo” human evolution is impossible is the phenomenon of mutation hotspots. Instead of changes occurring randomly throughout the genome—a key requirement for large-scale evolutionary theory—most mutations cluster in a relatively small number of locations which are commonly referred to as hotspots. As a result, the kinds of genome-wide changes required for evolution would rarely occur.

What the Research Community Admits

As Professor Guzmán et al. of the Centre for Genomic Regulation at The Barcelona Institute of Science and Technology explained,

“Mutations drive evolution and genetic diversity, with the most consequential mutations occurring in coding exons and regulatory regions.” He added, “the impact of transcription on germline mutagenesis remains poorly understood.”[1]

Here is a good AI summary of the literature in answer to the question “Why are mutational hotspots a problem for evolutionary biology?”:

Mutational hotspots complicate evolutionary biology by challenging core assumptions of randomness and uniformity in mutation rates across the genome and they challenge the traditional assumption that mutations are completely random and directionless. [2]

The existence of hotspots means that certain small genomic regions mutate much more frequently than others due to inherent molecular properties, such as DNA structure or repair mechanisms, making the mutational process non-random across the genome.[3]  Professor Horton of the Milner Centre for Evolution, Department of Biology & Biochemistry at the University of Bath, observes that traditional evolutionary models typically assume uniform mutation rates across the genome.[4] In reality, however, mutation rates vary dramatically, and context-dependent mutational biases—where even synonymous changes can alter a site’s mutability—pose a major challenge to such models. Horton et al. explain this away by describing the problem as merely “introducing complexity.” They also concede that,

… rarely, mutations can be beneficial. Advantageous mutations drive evolution and life’s ability to adapt to changing circumstances.[5]

Hotspot Evidence: Mutations Cluster, Not Scatter

Yet in two well-known examples, 98 percent of the mutations occur at only a single location, as shown in the following diagram:

One study found the vast majority of hot spots occurred at base number 199 of the gene.

Another example shown below is the location of hotspots in p53 colon cancer patients. The sample size was N=1,183. Although less extreme than the example above, almost 40 percent of all the mutations occurred in just 6 locations which were in the same area of the p53 gene (176-282) in a gene that was over 390 base pairs long.

Mutation hotspots (or mutational hotspots) are DNA segments that are especially prone to genetic alteration. The increased susceptibility of these DNA areas to mutation is attributed to interactions between mutation-inducing factors, the structure and function of the DNA sequence, and enzymes involved in DNA repair, replication, and modification.[6] The primary concern with mutational hotspots is their contribution to cancer because these hotspots can themselves cause cancer, further complicating the issue.[7] One major category of hotspot prone regions is CpG-rich sequences. Fully 3.1% of the 3-billion-base-pair human genome is classified as hotspot regions, including CpG-rich loci, which are common single-nucleotide-variant (SNV) hotspots in the germline.[8] Genetic mutations often arise when the body fails to repair damaged DNA accurately, resulting in small but irreversible damage to the genome.

New Findings on Transcription Start Sites and Mosaic Mutations

A new study found that the regions of the human genome most prone to mutation are the spots where RNA polymerase ‘opens’ the DNA in order to read the code and copy the genetic instructions. These regions, known as transcription start sites, are especially vulnerable to damage and imperfect repair. Such “mutations” are crucial to understanding the origins of many genetic diseases.[9]

The proposed explanation is that the extra “wear and tear where transcription begins” leads to a heightened rate of imperfect repair, producing genetic mutations. To evaluate this theory, the researchers analyzed human genome datasets covering 15,000 genes in more than 220,000 individuals, tracking mutations in these regions.[10] These are inheritable mutations that have persisted across multiple generations. From this analysis, the researchers concluded that mutation hot spots are more complex than previously assumed. The primary complication was the presence of mosaic mutations—changes that arise during the earliest stages of cell division after fertilization. Mosaic mutation is a common phenomenon; every human carries at least one cell with such a mutation. This discovery opens a whole new area of research aimed at understanding why mosaic mutations occur and what implications they may have for human health.[11]

A Growing Challenge for Evolutionary Theory

As Guzmán et al. aptly stated, “the impact of transcription on germline mutagenesis remains poorly understood” and the broader issue of mutational hotspots is likewise far from resolved. What is understood is that mutational hotspots pose a major problem for evolutionary models, and this issue is far more complex than previously believed—even prior to the work of Guzmán et al.[12]

 

 

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[1] Guzmán, M., et al., “Transcription start sites experience a high influx of heritable variants fueled by early development,” Nature Communications; https://doi.org/10.1038/s41467-025-66201-0, 26 November 2025.

[2] AI question posed November 30, 2025.

[3] Nesta, A., et al., “Hotspots of Human Mutation,” Trends in Human Genetics 37(8):717-729, 2021.

[4] Horton, J.S., L.M. Flanagan, R.W. Jackson, et al., “A mutational hotspot that determines highly repeatable evolution can be built and broken by silent genetic changes,” Nature Communications 12:6092; https://doi.org/10.1038/s41467-021-26286-9, 2021.

[5] Horton, et al., 2021.

[6] Written and fact-checked by The Editors of Encyclopedia Britannica, “What are mutation hotspots?,” https://www.britannica.com/question/What-are-mutation-hotspots, 2026.

[7] Chen, J., and R. Cho, “Emergence and evolution of mutational hotspots in sun-damaged skin,” Journal of Investigative Dermatology 138: 16e17; doi:10.1016/j.jid.2017.09.007, 2018.

[8] Nesta, Alex V., et al., “Hotspots of human mutation,” Trends in Genetics 37(8):717–729; doi: 10.1016/j.tig.2020.10.003, 13 November 2020.

[9] Starr, Michelle, “New ‘mutation hotspot’ discovered in the human genome,”

HEALTH; https://www.sciencealert.com/new-mutation-hotspot-discovered-in-the-human-genome, 28 November 2025.

[10] Guzmán, et al., 2025.

[11] Guzmán, et al., 2025.

[12] Nesta, et al., 2021.

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Dr. Jerry Bergman has taught biology, genetics, chemistry, biochemistry, anthropology, geology, and microbiology for over 40 years at several colleges and universities including Bowling Green State University, Medical College of Ohio where he was a research associate in experimental pathology, and The University of Toledo. He is a graduate of the Medical College of Ohio, Wayne State University in Detroit, the University of Toledo, and Bowling Green State University. He has over 1,900 publications in 14 languages and 40 books and monographs. His books and textbooks that include chapters that he authored are in over 1,800 college libraries in 27 countries. So far over 80,000 copies of the 60 books and monographs that he has authored or co-authored are in print. For more articles by Dr Bergman, see his Author Profile.