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There seems to be a built-in bias in evolutionary biology, which related to the original purposes of Darwin - and what he was trying to explain.
Darwin was trying to explain two things - the adaptation of species to their environment; and the origin of new species - and he argued that both used the same mechanism: natural selection. In other words, adaptations continue until they lead to new species; new species are explained by adaptation, so by Darwin's account adaptation is primary and speciation secondary.
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The context of these enquiries was a late world, a world full of various and competing species of many types, each seemingly fitted to its niche - but with on-going extinctions and a turnover of species across time.
Also, from Darwin's time the major selection pressures are assumed to be external and other than the organism itself: the organism's 'environment', its niche or adaptive zone - geography, climate, other species - including parasites and prey species.
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However, this context implicitly assumes that species are reproducing (as we would say, their genes are replicating) - this is taken for granted. And it takes for granted that the tendency of an organism to self-destruct (with ageing) and to fail accurately to replicate (to produce genetically defective offspring to due to new mutations and other forms of stochastic, entropic informational corruption) are not a significant problem - at most only modifiers of the basic story concerning adaptation and speciation.
In other words the external environment is regarded as primary, and the organism's internal environment - its integrity, cohesion and self-identity - is relegated to subordinate and secondary
But this is a late evolutionary perspective which takes for granted the preconditions of a world with reproducing and adapting organisms - it is a secondary, second-order account of natural selection.
The primary account of natural selection needs to explain how organisms do not become extinct; this problem of extinction must be overcome before adaptation can occur, and the possibility of speciation.
So the primary problem for a lineage is to avid extinction, and the problem of extinction due to internal causes is proximate and powerful. In a nutshell, any lineage will tend to decline in fitness and become extinct, due to the natural tendency for damage to the integrity of organismal information and to errors in information replication - unless natural selection first overcomes this innate tendency.
Thus, Natural Selection is primarily a Red Queen phenomenon, in which the problem for all organisms is to stay in the same place - against the natural tendency towards extinction.
Mutational damage and other forms of entropic damage to organisms will spontaneously occur and accumulate - therefore each lineage is on a treadmill sweeping it backwards towards extinction; and the basic and minimal function of natural selection is to keep the organism moving forwards at least as fast as the treadmill is tending to sweep it backwards.
But even when the Red Queen problem has been solved, the problem remains - underground and always operative. This perhaps is the best way of explaining the most basic original observation by Van Valen which led to the Red Queen idea - all species, no matter how long they have been in existence, are continuously vulnerable to extinction.
I interpret this as being the surface appearance of the underlying treadmill of mutational accumulation; always present, always operative, and so significant that it is always able to sweep any species to extinction if its control mechanisms fail too quickly and completely (although this extinction takes longer when the species has a large population, or enters a more favourable environment).
So, before adaptation, before speciation, first and foremost - Natural Selection must Prevent Extinction; and the organism's primary and unavoidable selection pressure that will lead to extinction unless counteracted is internal, not external.
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4 comments:
Consider by analogy a society or a civilization. It has a lineage transmitted through a cultural DNA. It faces external pressures, accumulates internal errors and possible advances, and purges some characteristics. It, too, is on a treadmill. It must reproduce itself or fall back on the treadmill and be replaced by something else. The modern West is not expanding based on numerical reproduction of its original members. There are three areas where the modern West is still expanding and exporting its civilization: technology, military dominance, and the mass media. East Asia is able to copy our technology, and the Middle East is able to absorb our military strikes. That leaves the mass media. Modern society is reproducing itself via the mass media indoctrinating its youth and exporting its views to the rest of the world in the hope that the larger world will adopt those views and cultural habits. This is a dynamic situation, and it is easy to see how it could end badly for the West, the confidence or pride of its elites in their own political correctness notwithstanding.
What you need to come up with now is a metric that correlates closely with the health of a species so that we can objectively measure the state and rate of change of the health of the species.
If - as you expect - the health of the human genome is deteriorating due to not culling mutation, then there is a pressing need for research to measure the health of a genome. Only when we are able to measure it and show the risk is there then any hope of convincing people of the need to alter behaviours which place the entire species at risk. Argument and discussion without a means to validate is not a powerful enough inducement to bring about the levels of funding required. People need to be convinced, and then that can change public policy, funding and with the right inducements - behaviour.
My suspicion is, that cancer research probably has the rudiments of a useful metric, but that all the pieces have not been assembled into a coherent method. (i.e. Inherited susceptibility and resistance.) Other types of expression of disease with a genetic component and the frequency of its expression in different communities and environments will likely also be a fruitful path.
One great irony may be that the miseries in such places as significant swaths of Africa may be where the human genome is strongest. Look to the places where life expectancy is low and especially where child mortality is high to see where the human genome is likely to be most healthy.
Mutational damage and other forms of entropic damage to organisms will spontaneously occur and accumulate - therefore each lineage is on a treadmill sweeping it backwards towards extinction; and the basic and minimal function of natural selection is to keep the organism moving forwards at least as fast as the treadmill is tending to sweep it backwards.
Beautiful and elegant analogy. So how do we determine whether we are above standing still, moving forward or heading towards extinction? (I have a vested interest in the outcome, as do we all.) There is a need for a method / metric that can be validated independently. No doubt there will be strong political opposition even to the idea, but it has to be visible and talked about by a wide audience.
The world wars of the Twentieth Century removed a large number of people from Europe's gene pool, but in the era of mass and mechanized warfare, it was arguably a perverse culling of the best and ablest young men on both sides.
Similarly those taking holy orders in the Middle Ages with the requirement of celibacy may have deprived the gene pool of some of its best and brightest, at least for those who kept their vows.
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