think fast

What do Tibetans and naked mole rats have in common?

Question 2.0 (1/25/2011):naked mole rat

A naked mole rat can be compared to:

The correct answer was A: a Tibetan.

Both Tibetans and naked mole rats have evolutionarily adapted to a low oxygen environment.

The low oxygen environments are different, however. The naked mole rat adapts to hypoxia in its burrows. It has a 40-million year history of living in sealed, subterranean tunnels where the air may be less than the typical 21 percent oxygen as low as 7.2 percent. The very low values occur in dense soils or during the rainy season or when the moles are actively digging new tunnels and using up a lot of oxygen.

Tibetans have a history of at least 10,000 years, and perhaps much longer, of adapting to high-altitude hypoxia. The air still has 21 percent oxygen but there are fewer oxygen molecules in a volume of air equivalent to a breath. For example, at 13,200 feet, each lungful of air has just about 60 percent of the oxygen molecules of a lungful at low altitude.

The oxygen transport systems of Tibet and naked mole rats (some are on display at the Cleveland Museum of Natural History in the mammal exhibit) have adapted somewhat differently. Naked mole rats have twice as much hemoglobin in their blood as other mammals. Hemoglobin is the molecule that carries oxygen. Making more hemoglobin is like getting a bigger sponge to soak up more oxygen. When people visit the mountains, they too produce more hemoglobin.

Tibetans are an exception to this general pattern. They don't have more hemoglobin than people that live in the lowlands, but appear to have adapted in a different way through breathing and circulatory mechanisms that enable them to live healthy lives at high altitude.

Question courtesy of Cynthia Beall, PhD, Distinguished University Professor and S. Idell Pyle Professor of Anthropology. In 2010, Beall's research resulted in the identification of a gene associated with Tibetans' low hemoglobin concentrations. Learn more about this discovery and other work by Beall.


Week Two Stats

How did you do? 163 people submitted answers for Question 2.0, 34 contestants selected the correct answer. Average time to correctly answer: 29 seconds. Fastest time? Nine seconds. Check out last week's top 10 players or visit the leaderboard totals for Weeks 1-2.

Take a shot at the next question, will be posted on Tuesday, April 26, 2011. See other past questions and answers.