An Uncomfortable Scenario

As a follow on from the previous blog about human evolution and cultural buffering, I wanted to play out some hypothetical, and possibly uncomfortable, future scenarios. One question I asked myself, as others have like Isaac Asimov in ‘A Choice of Catastrophes’, is what if we ‘buffer’ ourselves too much from nature? Are there any risks? Specifically, I am referring to the build up potentially deleterious mutations in a world where negative selection and so called purifying selection is significantly reduced. 

    To help explore this scenario I would like to introduce an analogy: Each successive mildly deleterious mutation adds another small item of baggage to the pack on someone’s back (this represents our genetic mutation load). As this pack grows in weight, another helium balloon is tied to it so masking the weight for the person and allowing him/her to go about their business (these balloons represent our clever cultural buffering). Now in this scenario I’m sure you can envisage a few things that could go wrong, besides having difficulty fitting through doors.

    Scenario 1: There is the dramatic case of a number of balloons being burst at once. In this case, people are quickly overloaded and are at risk of being crushed. Now selection would get to work and many people would find it all too much and collapse under the weight of their pack whereas a lucky few will by chance be better adapted to cope with the extra weight, will survive and reproduce children also able to cope. Now this scenario is frighteningly a distinct possibility with the rise of antibiotic resistant super bugs and the potential ‘post-antibiotic era’. Antibiotics have played a HUGE role in extending life expectancies and helping people fight off infections for the last 100 years or so. In our analogy, we are flying a model helicopter blindfolded around our balloons. Given our current reckless use of antibiotics in both medicine and agriculture, it is only a matter of time before we crash into our bunch of balloons unless we remove the blindfold and carefully land that helicopter safely on the ground.

    Scenario 2: A less dramatic scenario, but perhaps more insidious, is if we consider what happens when the production of new helium starts being outstripped by the weight we add. In this case we will reach the carrying capacity of our balloons and not be able to support any more baggage. One possibility here is if the pace of medical progress falters possibly because there is finite headroom into which to advance. One thing about humans, however, is that we have a knack of pulling the rabbit out of the hat with seismic advances in technology and understanding. Another angle is if the mutation rates increase which has been predicted to happen given our increasing exposure to mutagens and even our increasing age of parenthood. This scenario is harder to predict but something like the excellent film ‘Children of Men’ is a possibility. For example our increasing load may reduce fertility levels as the development from egg and sperm to baby is incredibly complex and genetically finely tuned. The increasing levels of infertility may be allowed to grow if families tend to have less children (already the case in many European countries). This would prevent any more ‘fertile’ people having more fertile children to re-populate as they would simply have children younger (or conceive easier) and stop there (using increasingly effective contraceptives, male pills coming soon!) while those less fertile would take longer to conceive, possibly having children later but would also just about reach their quota of one or two. Over time this precess would get harder and harder.

     So what are the possible solutions for our increasingly burdened descendants? Well assuming we navigate global disasters for long enough we might need to fight this hypothetical monster created by our technological advances with… more technological advances! A not too distant reality will be precise and simple genome editing (it is already possible and being carried out in human cells for research purposes in China and the UK with, suitably enough, a view to understanding infertility). Combined with a deeper understanding of what genes do, we could simply correct serious faults. Now I know this is a can of worms with enough ethical dilemmas and many obvious problems so I’ll leave it here and let that be a discussion for our future wiser selves. Yeah right.

UPDATE:  A recent study has demonstrated how caesarian sections have likely resulted in an increase in women with birth canals too narrow for natural birth. This represents a good emerging example of the issues discussed here. Before caesarian sections, women with narrow birth canals (due to narrow hips) would frequently die in childbirth often along with the child meaning the genes for narrow hips were 'purified' from the gene pool. Now, quite rightly, these women are given a chance not only to survive childbirth but keep their children who may well inherit the narrow hip genes. The modest 10 to 20% increase in the prevalence for narrow birth canals over the last 50 years is likely to rise still further given the medical necessity to save lives and the right and desire for women to have children. If we imagine a hypothetical scenario in which caesarian sections can no longer be performed (such as if antibiotics could not be relied upon) then we could see a widespread return to women dying in childbirth or such women avoiding childbirth completely as the buffering effect is lost!