Chapter 18.4, Problem 2CSC

Although it may never be possible to recover DNA from dinosaurs, ancient DNA of more recent vintage can help us understand more about the physiology and behavior of extinct animals. For example, researchers have extracted DNA from 43,000-year-old wooly mammoths that were preserved in the permafrost of Siberia. (Cold climates are especially favorable for preserving ancient DNA.) The investigators were able to sequence some of the DNA, including the genes that produced hemoglobin (a protein that transports oxygen in the blood). The researchers then inserted the mammoth hemoglobin genes into bacteria. The bacteria produced hemoglobin molecules just like those that circulated in the mammoth’s blood when it was alive.

Unlike hemoglobin from modern elephants, mammoth hemoglobin releases oxygen readily not only at core body temperature, but also at temperatures near freezing. Thus, though a modem elephant must keep its legs warm in order to provide oxygen to its leg muscles, a mammoth’s legs could get very cold and still function, an adaptation that helped the animals survive in ice-age Siberia.

In the end, mammoths became extinct, as do all species, eventually. What was responsible for history’s largest waves of extinction?