Survival of the fittest - what does it mean ?

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Mefiante (January 21, 2008, 12:31:24 PM):
New Findings Confirm Darwin's Theory: Evolution Not Random
Quote
Now, the findings of an international team of biologists demonstrate that evolution is not a random process, but rather occurs through the natural selection of successful traits.


It should be noted that the article is very, very badly titled.

'Luthon64
bluegray (January 21, 2008, 14:12:07 PM):
How do one go about to read the actual study?
Mefiante (January 21, 2008, 14:52:31 PM):
Here you go.

'Luthon64
Warm Lug (February 28, 2008, 22:55:39 PM):

Now other than noting that traits which become common are heritable, how were their favoribility actually measured?


From bacteria to kittens to humans:

Sickle-cell disease in humans is caused by a simple and well-understood mutation. It is inheritable in the same way that blue eyes are. This, otherwise, somewhat debilitating disease occurs more commonly in people (or their descendants) from parts of the world where malaria is or was common, but it also occurs in people of other ethnicities. This is because those with one or two alleles of the sickle cell disease are resistant to malaria since the red blood cells are not conducive to the parasites - in areas where malaria is common there is a survival value in carrying the sickle cell genes.

I see no problem with cause and effect here, and no problem with measuring the survival value that the mutation confers to the "victim".

ArgumentumAdHominem (February 29, 2008, 21:27:45 PM):
Sickle-cell disease in humans is caused by a simple and well-understood mutation.

There is another related blood disease which has a similar effect. 16% of the population of Cyprus (and lower percentages of the population of nearby Mediterranean countries) suffer from thalassaemia which was seen for centuries as a curse, having a visible presentation in the formation of facial features and causing shorter life expectancies for those afflicted. As a result of the prevalence, all islanders carry the gene (most in the recessive form) and every Cypriot is immune to malaria.

I first heard about this story in a brilliant documentary by the geneticist Professor Robert Winston (not sure if it was "Threads of Life" or "The Human Body"). His point was that our understanding of genetics may lead us to want to "prune-out" genetic disorders like these and lose undiscovered benefits such as malaria resistance. If we discovered genes which cause certain heritable diseases, would pruning them from the genome help us or possibly introduce a weakness to diseases discovered in the future or future mutations of current life-threatening diseases?

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