In 2005, Dr. Luis Rosero, a Costa Rican demographer trained in the U.S, presented a paper at an international conference claiming to have discovered that 60 year-old Costa Ricans have the longest life expectancy of anyone in the world. In other words, if you are middle aged and live in Costa Rica, you are more likely to reach, say, a healthy age 90 than your counterparts worldwide. The academics at the conference did not believe Dr. Rosero. After all, Central America is still considered “Third World,” a place of poverty, tropical disease, and, during the 1990’s, terrible wars. How could the people here live longer than “First World” countries like those in Europe and the U.S?