A genetic mutation occurs when mistakes are made during copying/reproduction of genetic code. Mutations may be beneficial, neutral or deleterious (bad) for the organism. Around 95% of mutations have no significant immediate effect or are neutral, and most remaining ones are deleterious. Mutations are unavoidable and they are necessary for evolution to work at all. Natural and sexual selection decide which phenotypes will be prevalent in future generations and which mutations will become fixed (meaning highly prevalent in the gene pool).
Older parents produce more mutations in their offspring. There is also evidence that the mutation rate is much higher in human males (up to 6 times higher), which has also been found in other species such as birds. This has lead to a hypothesis of evolution being largely driven by mutations in the male germline. This finding is heavily contested, however.
Massively reduced infant mortality may be the main driver of a recent increase in overall mutational load, leading to a higher incidence rate of disease, autism, obesity, sinistrality (left-handedness), asymmetry etc.
Kinds of mutations that can occur[edit | edit source]
There are various main types of mutations:
|Deletion||one or more DNA bases are left out||a piece of chromosome is lost, together with any genes which may be on it.|
|Insertion||one or more extra base is put in||a smaller chromosome is added into a longer chromosome|
|Substitution||one or more bases are changed for another base in the sequence|
|Duplication||whole genes are copied||part of a chromosome is repeated|
|Inversion||part of a chromosome is reversed end to end|
|Translocation||part of a chromosome gets moved onto another chromosome|
Rise in mutations[edit | edit source]
Some evidence suggests that there are more people with deleterious mutations in the human population due to a number of factors, including but not limited to: milder ecological conditions, modern medicine, advanced paternal age and especially due to much lower infant mortality. Due to the economic cost associated with a degraded gene pool, the demographic transition can be considered an instance of the tragedy of the commons as the externalities of the degraded gene pool are foisted off on future generations at the benefit of avoiding the near-term costs of having women birth many children (rather than work) and the cost of a high mortality selection pressure on the offspring.
Given the complex nature and function of the human brain, one would expect it to be particularly vulnerable to deleterious mutations, which may be reflected in the apparent rise in the prevalence of Autism Spectrum Disorders, as it has been argued that up to 30% of cases of this condition in simplex families (where only one member has the condition) could be attributed to de novo mutations. Extrapolation of the rate of deleterious mutational load in mice and other organisms has led to a rough estimate of a 1% decline in the baseline physical and mental performance attributes of populations in conditions of extreme relaxed selection pressures (both natural and sexual) per generation. This estimate may be overly conservative, however, particularly in regards to brain function.
In terms of human intelligence and mental function, it has been asserted that general intelligence has declined due to increasing mutational load in the human genome, though deleterious mutations appear to only account for up to 7% of the secular decline in general intellgence. Other factors, such as a general negative correlation between intelligence and fertility (particularly among women) and the pollution of the environment with neurotoxins that disrupt brain function and development post-industrialization, appear to be more to blame for this apparent decline in general intelligence, a decrease that appears independent of secular increases in IQ test scores due to the Flynn Effect.  Some researchers have also argued factors that decrease deleterious mutational load in populations, such as reductions in the rate of inbreeding and pre-natal therapeutic fetus selection (the abortion of offspring with severe abnormalities revealed through pre-birth screening) may serve to counteract these effects somewhat.
Mutational load may not be related to economic status very much. On the one hand, less mutated individuals are expected to rise higher in the socioeconomic hierarchy. On the other hand, the elite has a slightly lower infant mortality rates, milder living conditions and sometimes engages in excessive inbreeding, which may lead to the lower classes (who had been under conditions of Darwinian selection for longer, due to their lower standard of living) to be less mutated. Also, higher mutational load is only weakly related to certain traits important for socioeconomic success, such as general intelligence, so one would expect that a lot of these highly mutated individuals would still be able to attain positions of social and economic influence.
Some incels may have a high mutational load[edit | edit source]
For example, incels on incels.co disproportionately describe themselves as autistic and autists have a high risk of inceldom. Autism has been suggested to be a good measure of developmental instability/mutational load due to the correlations with de novo mutations mentioned above.
A high load of deleterious mutations appear to degrade the general quality of the phenotype, so people with a higher mutational load may be less physically attractive on average. High mutational load is associated with greater fluctuating asymmetry, though the effects of higher levels of this trait on physical attractiveness and overall mating behavior seem mixed, partly due to poor quality research and differing methods of measuring this trait.
Paul Erhlich, the author of the book The Population Bomb, a work with a fearmongering Malthusian tone which warned of the catastrophic effects of overpopulation, has also claimed that the size of the modern human jawbone is much smaller than it was pre-modernization. Like Mike Mew, he mainly blames environmental factors like mouth-breathing, and modern food processing techniques making food require less effort to chew, though Erhlich also attributes some of this claimed decrease in jaw size to modern environmental pollutants disrupting the regular development of the jaw. Some of this decrease may also be due to increasing mutational load or selection pressure against larger jaws, though it seems these factors are insufficient to explain most malocclusions, or the secular decrease in jaw size, given the low frequency of the affected gene variants and the apparent rapid pace of this change in jaw size.
It is also not known how much of a role smaller jaws would play in reducing physical attractiveness. Overall facial masculinity is only weakly (if at all) linked to male physical attractiveness and lifetime mating/reproducive success, though mutations that would result in oddly shaped or maloccluded jaws would be expected to reduce physical attractiveness significantly.
Deleterious vs beneficial mutations[edit | edit source]
Even though the vast majority of mutations are harmful or neutral, some mutations are beneficial. Mutation accumulation is how evolution works, adaptive mutations are preserved, and deleterious mutations (depending on ecological context) are eventually purged from the gene pool. An example of a beneficial mutation is the ACTN3 gene giving West African sprinters faster fast-twitch muscle fibers and a faster sprint speed.
Ugliness does not necessarily worsen the gene pool as it is only weakly related to disease, though it is generally socially undesirable. However, various genetic diseases, functional and cognitive impairment, do warrant concern and reduce overall population viability if maintained in the gene pool (dysgenics). Some experts have made dire predictions that the buildup of deleterious mutations in the human genome possibly spells disaster for the human race, such as Alexey S. Kondrashov, a prominent ecologist and evolutionary biologist. Kondrashov, in particular, argues that removal of formerly harsh selection pressures (like high rates of infant mortality and disease burden) that historically served to limit the buildup of deleterious mutations in the human genome will lead to the proliferation of these deleterious mutations in the species, resulting in unprecedented increases in genetic diseases like autism, schizophrenia, and diabetes, etc.
He also argues that this removal of selection pressure has also resulted in potentially maladaptive or undesirable traits like obesity, psychopathy, and other socially undesirable traits increasing in prevalence. A counterpoint to this argument would be that the increases in many of these 'deleterious' (in a subjective sense) mutations may be due to them actually increasing the fitness of the bearer in the context of modern society. These mutations could be beneficial in that they currently increase the organism's fitness, but would possibly be deleterious in other cultural or social contexts.
Kodrashov is staunchly against eugenics and concludes that deleterious mutational accumulation can only be ethically and effectively be resolved via bioengineering technologies like gene editing. He discusses the various ethical quandaries surrounding the use of these technologies and the likely far-reaching social implications of their deployment at some length in the book. Substantial progress has already been made towards the development of these technologies, in particular, strides have been made in correcting deleterious mutations in embryos via gene editing.
Perhaps the focus on deleterious mutations from the news media and others is because bad news is more attention-grabbing, humanity seems to have a negativity bias. People are also possibly hardwired to socially exclude individuals with certain deleterious mutations in an effort to increase their own reproductive success, and possibly also prevent these individuals from hampering group-cohesion/co-operation (in the case of deleterious mutations that damage social processing and social functioning, such as ones linked to autism).
See also[edit | edit source]
References[edit | edit source]