May 13, 2010
Tibetans Genetically Adapted To High Altitude

Tibetans carry several genetic variants that adapt them better to high altitude living.

SALT LAKE CITY—Researchers have long wondered why the people of the Tibetan Highlands can live at elevations that cause some humans to become life-threateningly ill – and a new study answers that mystery, in part, by showing that through thousands of years of natural selection, those hardy inhabitants of south-central Asia evolved 10 unique oxygen-processing genes that help them live in higher climes.

In a study published May 13 in Science Express, researchers from the University of Utah School of Medicine and Qinghai University Medical School in the People's Republic of China report that thousands of years ago, Tibetan highlanders began to genetically adapt to prevent polycythemia (a process in which the body produces too many red blood cells in response to oxygen deprivation), as well as other health abnormalities such as swelling of the lungs and brain (edema) and hypertension of the lung vessels leading to eventual respiratory failure. Even at elevations of 14,000 feet above sea level or higher, where the atmosphere contains much less oxygen than at sea level, most Tibetans do not overproduce red blood cells and do not develop lung or brain complications. The Utah and Chinese researchers found evidence that this might be related to at least 10 genes, two of which are specific genes strongly associated with hemoglobin, a molecule that transports oxygen in the blood.

Tibetans have had more time to evolve for better fitness at hgh altitude than other groups that live at high altitude. For example, the Amerinds in high altitude areas of Peru have genetic adaptations to altitude but their adaptations aren't as sophisticated (sorry, no cite, read this a few years back). Evolutionary pressures haven't acted on them long enough to bring forth the best genetic variants for high altitude living.

Han Chinese are not genetically adapted well to high altitude. Tibetan women give birth to bigger babies than Han Chinese women at the same high altitudes. The Han Chinese women have more adverse pregnancy outcomes at high altitudes.

Various human populations around the world evolved to better adapt to local conditions. Immune systems, digestive tracts, skin color, height, and other physical attributes and functions evolved pretty rapidly once humans left Africa. This evolution was probably sped up by mating with Neandertals.

I am curious to learn which personality and other cognitive traits were seleced for to adapt humans to local environments. For example, did being a fisherman work better for certain personality types while other personality types worked well for crop farmers or herdsmen?

Share |      Randall Parker, 2010 May 13 05:52 PM  Evolution Human Nature


Comments
mike shupp said at May 14, 2010 12:52 AM:

I dunno about that putative advantage of mating with Neandertals.
If I recall correctly, humans didn't really start colonizing the
Alps and other high altitudes (over 2000 feet let's say) until
the Holocene.

There isn't archaeological evidence of humans at high altitudes
until 5000 BC or so. And it seems plausible that under true
glacial conditions, high altitude sites would have been pretty
barren in terms of food. If you're going to live on elk found at
sea level, you might as well live at sea level.

Granted, there are many references to Neandertals and early Homo
sapiens sapiens at "Mount Carmel" and similar sites, but next to
the Alps these are foothills.

Chris T said at May 14, 2010 2:38 PM:

"I am curious to learn which personality and other cognitive traits were seleced for to adapt humans to local environments."

A good question, but do we really want to know the answer?

Sycamore said at May 15, 2010 4:49 PM:

> high altitude sites would have been pretty
barren in terms of food. If you're going to live on elk found at
sea level, you might as well live at sea level

There's not much food in the desert either, but people have long lived there. Rich lands are crowded.

PR said at May 18, 2010 12:32 PM:

"I am curious to learn which personality and other cognitive traits were selected for to adapt humans to local environments."

Me too - I cannot help but to believe that those who got off of their butt (under their own motivation) and fled Europe to the US, and particularly to New England, were totally different from those who now exist there (there being both Europe and New England). Are both Europe and New England what they are today because the people with those traits kept moving West towards more conflict (adventure, frontier, or however you want to describe it) until the traits were diluted out or were the traits diluted out in situ? After all, the Quakers were a great component of the huge murderous N. E. whaling industry.

Some desert Indian peoples of the southwest have metabolic adaptations that permitted them to eek more calories out of the desert environment than do Europeans but now it disposes those on modern diets to diabetes rates approaching 50% as adults. Historically, desert peoples were thought to be driven to the desert by more aggressive neighbors - or did they self marginalize to the desert to avoid conflict and thus doom themselves to modern dietary perils, which is not relieved by fast enough gene flow due to cultural (cognitive traits) pressure to not out breed? Or did cultural pressure to not out breed cause self marginalization?

Chris T. said: "A good question, but do we really want to know the answer?"

Today in the US academic environment, I don't think you can even ask those questions without being called racist, the epithet of the simpleton.

bs said at June 6, 2010 8:41 AM:

Chris T, you appear to respond better to trends rather than truth. I respect truth above everything, whether I like it or not is a different matter, but as far as I am concerned, human evolution, which is now predominately knowledge-based, can only occur if we embrace truth. Anything less is devolution. If it's true, I want to know it. It is then my responsibility of how I deal with it.

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