Posted by: scienceguy288 | January 22, 2008

Darwin on Sherpas

Hey, maybe there is something to this whole “natural selection thing.” (Note: sarcasm)  According to Case Western University anthropologist Dr. Cynthia Bell, women who have the ability to carry more oxygen in their blood have more than twice as many surviving children as women who cannot carry as much oxygen. This is apparently a very strong example of natural selection at work in the human species. 

tibet.gif

A group of Tibetan Women in the Himalayas

Women who carry a copy of a specific version of a gene (an allele) that encodes the production of high oxygen saturated hemoglobin, a protein that carries oxygen to muscle tissues for production of ATP (energy), have 125% more surviving children.  The specific gene has not been identified, but it is being worked on. 

So how does that work?  Well, women with that genetic allele will survive better in the high altitude Himalaya Mountains where oxygen is thin.  They then are able to pass on that allele to their children, who in turn, survive better in that environment than children without the allele.  This is an example of natural selection, “the process by which organisms that are better suited to their environment than others produce more offspring. As a result of natural selection, the proportion of organisms in a species with characteristics that are adaptive to a given environment increases with each generation. Therefore, natural selection modifies the originally random variation of genetic traits in a species so that alleles that are beneficial for survival predominate, while alleles that are not beneficial decrease. Originally proposed by Charles Darwin, natural selection forms the basis of the process of evolution (http://dictionary.reference.com/browse/natural%20selection)” (just in case you were born in the deep south and never heard of this). 

We humans love to think that we are not animals and therefore somehow above of the theory of natural selection.  We are not.  This is why people with genetic diseases do not survive to have children: their genes will not be passed on.  This is just another example that we are all tethered to the boundaries of the natural world.

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Responses

A science blog– neat! I like to think that I’m a bit of a citizen scientist (no formal training but plenty of enthusiasm and curiosity)

Did you take the picture from the Himalayas?

By: Jim on January 22, 2008
at 10:33 pm

Hey Jim, I wish. I would like to go there, but I just found this picture on a search engine. Just wondering…is it normal blog protocol to site the pics/sources if you did not take them?

By: scienceguy288 on January 22, 2008
at 11:44 pm

Cool man! I like how you are sticking with the winter theme.

I think you can be a great blogger. Keep up the good work.

By: edinho11 on January 23, 2008
at 12:23 am

It wasn’t a conscious theme, but hey, if it works for you. Maybe it is just this cold weather we’ve been having that is influencing my writing.

By: scienceguy288 on January 23, 2008
at 1:09 am

After spending 2 months working in Bolivia (and going back shortly), yeah, high altitude is an amazing thing.

Unfortunately, it ages a person quicker (just an observation from looking at the women.)

And, I added you to my blog roll. thanks for adding me to yours.

R(etc..)

By: rtd13 on January 23, 2008
at 2:21 am

If I may interject a non-naturalist perspective: It’s a common misconception that creationists (young or old earth) deny natural selection. The real question is: can natural selection alone account for the origin of new species (divergence) or simply the selection of existing species (convergence). All examples of natural selection I have seen illustrate convergence. Even among evolutionists the question is highly controversial.

Another general common misconception is that a survival advantage more or less guarantees survival of that advantage-producing attribute. The reality is much more complex and many advantages get buried by the ‘noise’ of daily complexities.

Consider even a simple contrived experiment of a room with mice in which there are 2 varieties of cheese. Cheese A is yellow and nutritious whilst Cheese B green, toxic and fatal. Obviously you will soon select for the mice (yellow mice) who prefer yellow cheese and can claim this preference is a survival advantage. However consider the case where Cheese A is 0.1% more nutritious than Cheese B. All things being equal, yellow mice will eventually dominate. The reality is that all things are not equal and the nutritional difference is insignificant and thus yellow mice have zero survival advantage. Not 0.001 but 0!

By: cawoodm on January 23, 2008
at 4:08 pm

I do not see how all examples of natural selection you see illustrate convergence. Admittedly, some do, but natural selection is a mechanism for diversity as well. Natural selection allows populations to adapt to the specific environments in which they live. Since populations of organisms live in varying environments, populations have different combinations of traits. Diversity is beneficial to a species because diverse populations are more likely to have some members survive when environmental conditions change. And, sooner or later, environmental conditions will always change causing species to change through natural selection. If there is conflict between species over resources, the animals will adapt through natural selection to a specific niche.
For example…Finch A likes to eat seeds in cacti. Through natural selection, the finches with longer beaks will survive better and produce more offspring (who carry the gene for longer beaks) eventually, some of these Finches will evolve into a new species, but some will not and remain Finch type A (they may just go to a different ecological niche).

By: scienceguy288 on January 23, 2008
at 6:33 pm

Finches are a good example of convergence because as the environment gets more extreme only certain sub-species (e.g. long beaked) remain. Contrary to textbook examples (i.e. that climatic extremes encourage divergence) it’s the milder climes that encourage diversity.

Interesting as all this is, it’s variance of a characteristic within a species (micro-evolution) and demonstrably cyclic (because climate is cyclic). The textbook extrapolations that macro-evolution = lots of micro-evolutions thus appear to be wishful thinking and fallacious. Thus, the debate rages on within the evolutionist camp.

By: Marc on January 25, 2008
at 8:27 am

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