I hope that strong AI and practical gene editing becomes a reality before this bleak future kicks in.
GENETICS March 7, 2016 vol. 202 no. 3 869-875; DOI: 10.1534/genetics.115.180471
Mutation and Human Exceptionalism: Our Future Genetic Load
Michael Lynch
Although the human germline mutation rate is higher than that in any other well-studied species, the rate is not exceptional once the effective genome size and effective population size are taken into consideration. Human somatic mutation rates are substantially elevated above those in the germline, but this is also seen in other species. What is exceptional about humans is the recent detachment from the challenges of the natural environment and the ability to modify phenotypic traits in ways that mitigate the fitness effects of mutations, e.g., precision and personalized medicine. This results in a relaxation of selection against mildly deleterious mutations, including those magnifying the mutation rate itself. The long-term consequence of such effects is an expected genetic deterioration in the baseline human condition, potentially measurable on the timescale of a few generations in westernized societies, and because the brain is a particularly large mutational target, this is of particular concern. Ultimately, the price will have to be covered by further investment in various forms of medical intervention. Resolving the uncertainties of the magnitude and timescale of these effects will require the establishment of stable, standardized, multigenerational measurement procedures for various human traits.
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Given that Cro-Magnons and Neanderthals exhibited cranial capacities in the 1800cc range, and modern human populations are typically in the 1300-1400 range, I would say we have fallen quite far. We are closer to homo heidelbergensis in terms of brain size than the first AMH. Of course size is not the only factor, there is encephalization and greater prefrontal cortex development to consider, but the trend still points towards decline. Hopefully whatever catastrophe this inevitably leads to will not be the end of our species entirely.
This is dysgenic only in the paleolithic environment. It is obviously adaptive in the modern agricultural/industrial environment. Why don't biologists learn something about evolution and natural selection?
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