Thursday, 25 September 2014

The primacy of the Red Queen. Or, what does natural selection mainly explain? Yes Speciation and Adaptation; but primarily it *Prevents Extinction*

*
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.

*

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.

*

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.
*