Devolution



Devolution: small populations - loss of information - inbreeding

Following the previous two problems Gould and Eldredge proposed in 1972 under an alternative explanation for the name of the punctuated equilibrium: they assume that fossils provide a good picture of what actually happened, namely: the majority of the populations do not evolve and are supposedly balanced. Namely, evolution takes place in small populations in remote areas where hardly any fossils are to be found. This would explain the jerky pattern in the fossils and also provides a solution to the problem of population genetics which large populations can hardly evolve.


Punctuated equilibrium

This modified theory of the punctuated equilibrium of previous problems does not quite resolve, because by limiting development to small populations, one also has fewer mutations available. The modified theory does give rise to a third problem: it is well known that small populations easily fall prey to inbreeding and will finally die out. The Pandabeer and Swedish wolf are current examples. The process of chance and natural selection gives in theory and in practice earlier rise to devolution. So large populations can hardly evolve, while small populations evolve in the wrong direction.

Interestingly, the fossils do illustrate this devolution. The known evolution of the horse is a good example of not only the horse's evolution shows a loss of toes need to 1 toe (devolution in itself), but the pattern in the fossil record also shows that the horse in different periods are going through the same evolution in different places, each time diversifies quite suddenly and dies. Since Europe at that time was an archipelago, is it logical to assume that becoming isolated on islands with small populations results to inbreeding, whatever sudden diversification and extinction of the horse can explain. The modern horse on the other hand comes from a large population in America which evolved much less.

Some may wonder: how is it that natural selection does not prevent inbreeding? As explained just now, alongside natural selection chance also plays a role, and for typical mutations chance plays an even greater role than natural selection because the selective advantage is usually quite small. And since there are so many more harmful than beneficial mutations, devolution is actually obvious. Natural selection is simply less effective than is often realized. This is noticable as an example in harmful but recessive genes that are inherited but it's only reflected when both parents pass the gene. This creates "genetic load". Macro-evolution is therefore less likely than people often think, even taking into account natural selection.

The three issues we have discussed up to this end, are so-called 'old' problems that were already known before 1970. The following two problems are 'new' problems especially the last 20 years to attract attention. These problems were detected by microscopic examination of the living cell, which appears much more complex than they had ever imagined.