I hope everybody has seen/read the recent PNAS supplemental issue: In the light of evolution I: Adaptation and complex design- there are several way cool papers directly relevent to the stuff I blog about here, and to the stuff that many of you are interested in. It’s worth a read..
Anyway, the there is a paper about adaptive evolution to persistant hypoxia- as it related to living at very high altitude, as do the people of the Andes and in Tibet. Aside from the more well known issue fo intense solar radiation, there is actually a lot less O2 available for metabolism at altitudes >4,500 meters than there is at sea level. Here is the graph:
This is the reason people talk about how difficult it is to play pro sports in Denver, the partial pressure of inspired oxygen is just so much less.. Now double the altitude… and try and live there for live. Hard manual labor is nearly impossible for the non-native, hell, even walking up stairs leaves you short of breath. Having lived in La Paz Bolivia (~4000m) I know…
Anyway, the point of the paper is to describe the adaptive evolutionary process- which turns out to be different in Tibet than it is in the Andes… A nice demonstration of how pre-existing genetic variation + rand0m processes coupled with strong selective pressure yields different outcomes..
If this originated with “a designer”, wouldn’t she have used the same design both times- why invent 2 processes to deal with the same problem. Certainly it would be wasteful and inefficient…. Not my idea of something worth worshiping.
Ok, before I talk about the ways in which these people have adapted, I’ll tell you that endpoint physiological parameters are similar for lowlanders and people living at high altitude. Basal metabolic rates and maximum oxygen uptake are identical. This means that through whatever mechanism, High-landers have the full aerobic potential that low-landers have..
Adaptation:
- Minute Volume- This is the volume of air you breath in one minute. Obviously, more volume means more oxygen molecules per unit time. One obvious way to compensate for low concentration of oxygen is to breath more. Turns out, the Tibetan people do this, NOT the Andean…
- Red Blood Cells- Basically, have more red blood cells, deliver more oxygen to tissues.. Andean people have more that lowlanders, The Tibetans do not.
- Oxygen Saturation- Is normal in Andean populations, low in Tibetan.
- Oxygen saturation and RBC concentration taken together gives us Arterial oxygen content, graphed t the right. As you can see, the tibetan people are really hypoxic, and must maintain normal metabolic function through other means…Hmmm
- Pulmonary Artery Pressure (PAP): As the PAP increases, blood flow to the lungs decreases and oxygenation decreases. In Tibetans, the PAP is low relative to the Andeans, and this might compensate for the low arterial oxygen content. Moving outside the lungs, Tibetans seem to have high blood flow in their whole bodies- brain, muscles, etc..
- Capillary network Density: which could potentially improve perfusion and oxygen delivery, because each capillary would supply a smaller area of tissue, and oxygen would diffuse a shorter distance. Tibetans have higher density capillary networks than do Andeans
Ok, Ok, Ok, so there are a bunch of potential adaptations… The real question is whether these arose via natural selection. The necessary criterion for natural selection are the following.
- Heritable variation
- Differential reproductive success
I won’t delve into these issues, but basically the authors cite papers that show many of the key physiologic parameters and putative adaptations have significant values for h^2, especially in Tibetan populations. They also cite a paper that demonstrates that there is significant survival/fitness value for people that possess these traits…
Cool stuff, and a nice illustration of how there evolution, given several independent starting points, can find multiple reasonable solutions.. While biology has certainly been guilty of over playing the adaptation card- adaptation, when it can be demonstrated, is so cool.
2 responses so far ↓
1 Laurent // May 31, 2007 at 3:01 pm
Heritable variation is only required for evolution to occur (whether adaptively or randomly).
Natural selection happens even in the absence of heritable variation, say if a phenotypic trait is plastic (or even if there’s just environmentally based variation), there might be differences in reproductive success (therefore natural selection).
2 Anonymous // Jun 1, 2007 at 10:13 am
Change is not evolution, until it creates anothere kind of life form.
If evolutionists want to end the arguments all they have to do is, get their brilliant heads together and assemble a ’simple’ living cell. This should be possible, since they certainly have a very great amount of knowledge about what is inside the ’simple’ cell.
After all, shouldn’t all the combined Intelligence of all the worlds scientist be able the do what chance encounters with random chemicals, without a set of instructions, accomplished about 4 billion years ago,according to the evolutionists, having no intelligence at all available to help them along in their quest to become a living entity. Surely then the evolutionists scientists today should be able to make us a ’simple’ cell.
If it weren’t so pitiful it would be humorous, that intelligent people have swallowed the evolution mythology.
Beyond doubt, the main reason people believe in evolution is that sources they admire, say it is so. It would pay for these people to do a thorough examination of all the evidence CONTRARY to evolution that is readily available: Try answersingenesis.org. The evolutionists should honestly examine the SUPPOSED evidence ‘FOR’ evolution for THEMSELVES.
Build us a cell, from scratch, with the required raw material, that is with NO cell material, just the ‘raw’ stuff, and the argument is over. But if the scientists are unsuccessful, perhaps they should try Mother Earth’s recipe, you know, the one they claim worked the first time about 4 billion years ago, so they say. All they need to do is to gather all the chemicals that we know are essential for life, pour them into a large clay pot and stir vigorously for a few billion years, and Walla, LIFE!
Oh, you don’t believe the ‘original’ Mother Earth recipe will work? You are NOT alone, Neither do I, and MILLIONS of others!
Leave a Comment