What insights into biological systems have been discovered through isotope analysis?
The opening investigation of dinosaurs (oxygen atoms) and the investigating life experiment of hamburgers (carbon atoms) are examples of identifying the life history of organisms through isotopic analysis. Recently, this has been applied to humans as well. Hair is a living tissue, with a lot of O and H atoms derived from water in the diet. Ecologist Jim Ehleringer and chemist Thure Cerling have shown that like the dinosaurs, the isotopic ratios of O and H in hair reflect the geographical region where a person drank the water. This can be useful evidence in a forensic investigation, placing a person at a location. Isotopic ratios are also used to identify where plants are grown, because their tissues also have unique ratios. For example, ratios have revealed the geographical origin of poppies used to make heroin. The mass spectrometer, a chemical analysis instrument that detects isotopes, is fast becoming an important tool for biologists.
Future directions
Tracking the isotopes of oxygen and hydrogen in precipitation is useful in understanding patterns of climate change. Water evaporates in warmer regions at the tropical latitudes on Earth and moves toward the cooler poles. As an air mass moves from a warmer to a cooler region, water vapor condenses and is removed as precipitation. The heavy isotopes of H and O tend to fall as precipitation more readily than the lighter isotopes, so as the water vapor moves toward the poles, it becomes enriched in the lighter isotopes. The ratio of heavy to light isotopes that reach the poles depends on the climate—