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Author Topic:   Evolving New Information
Hyroglyphx
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Posts: 5858
From: Austin, TX
Joined: 05-03-2006
Member Rating: 2.3


Message 359 of 458 (524740)
09-18-2009 10:46 AM
Reply to: Message 357 by Coyote
09-18-2009 10:25 AM


Re: Beneficial mutation--and your worldview
That is evidence of a beneficial mutation in relation to malaria, although the same mutation is not beneficial in some other circumstances.

Sickle Cell Anemia is a recessive trait that tends to have more problems than benefits. You may be less susceptible to malaria, but more prone to dropping dead. Your cells need oxygen all of the time, versus the risk of contracting malaria some of the time. I really don't see that as being a beneficial mutation when the cost outweighs the gains, regardless of whether or not you live in an area of the world where malaria is prevalent.

Edited by Hyroglyphx, : No reason given.


"Three passions, simple but overwhelmingly strong, have governed my life: the longing for love, the search for knowledge and unbearable pity for the suffering of mankind." -- Bertrand Russell

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 Message 361 by NosyNed, posted 09-18-2009 11:08 AM Hyroglyphx has responded

  
Hyroglyphx
Member
Posts: 5858
From: Austin, TX
Joined: 05-03-2006
Member Rating: 2.3


Message 363 of 458 (524756)
09-18-2009 12:26 PM
Reply to: Message 361 by NosyNed
09-18-2009 11:08 AM


Re: Benefits vs Problems
Define "more" please. How do you measure it?

How I rationalize it is that all human beings, regardless of where they live, need oxygenated blood cells, even those who live in an malaria-stricken area.

If it had more problems than benefits it would be selected out of the population would it not?

That all depends on how long sickle-cell anemia has been around. If we can definitively conclude that it has been around for centuries upon centuries then, yes, what you say is true. But if this is a relatively new mutation, then we wouldn't expect it to be selected out or in just yet.

In fact, it has a net benefit to a population in the right circumstances. This is enough to bring the single copy up to about 1/3 of a population. Higher than this and there are too many two copy individuals born.

How would this be the case? Wouldn't it be the opposite? If Africans tend to procreate with other Africans, then the more people who have the hetereozygous trait run a greater risk of procreating with someone with the same condition, so that their children might be the homozygous carrier. Would not that homozygous trait increase as population increases?

It isn't so easy to be absolute about what is beneficial and what isn't. One example that appears to be easy is the mutation in a strain of Italians that appears to make them immune to cardiovascular disease (this arose some centuries ago in one individual). Another example that is a bit less clear is the boy who has super muscular development. Being very strong should be beneficial should it not? However, in an environment that has limited food availability it may not be. This selective pressure can reduce the average size of populations under some circumstance (foor shortages) but under other circumstances push a population to larger sizes (cold weather).

Very true. Even the greatest benficial mutation may have some unforseen drawback. That could be said of all traits I suppose.

Edited by Hyroglyphx, : fixed html


"Three passions, simple but overwhelmingly strong, have governed my life: the longing for love, the search for knowledge and unbearable pity for the suffering of mankind." -- Bertrand Russell

This message is a reply to:
 Message 361 by NosyNed, posted 09-18-2009 11:08 AM NosyNed has responded

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