Evolution and health
This month marks the birth of the 19th century naturalist Charles Darwin, who launched the scientific study of evolution. While Darwin's theory laid the groundwork, ongoing studies have deepened our understanding of evolution, including how it relates to health. Research funded by the National Institutes of Health has helped answer many questions about evolution, health and medicine. Here's a sampling.
How is evolution relevant to health?
Considered by scientists as the central unifying concept of biology, evolution is a set of complex processes by which populations of organisms change over time. Evolution results in genetic adaptations that allow organisms to survive, be healthy and thrive. For example, humans have evolved digestive enzymes that break food into nutrients, immune systems that can both eliminate harmful microbes and co-exist with helpful ones, hormones that enable the "fight or flight" response, and traits that allow populations to live at high altitudes.
Can evolution help us understand why we get sick?
Yes. There are many reasons why we get sick, including being exposed to environmental hazards or having certain combinations of genetic variations that predispose us. But a key reason is that we're surrounded by other living — and evolving — creatures. For example, some strains of bacteria have genes that enable them to evade the antibiotics designed to kill them, allowing infections to continue. The flu virus also evolves, changing rapidly from year to year and helping to explain why new vaccines must be developed. Scientists carefully monitor this evolution to help ensure that each year's vaccines are effective against the most dominant strains in circulation.
Why do disease-causing mutations persist?
There are several reasons. Some mutations can have both beneficial and harmful effects, depending on the circumstances. Other mutations persist because they don't impair our ability to survive and reproduce. And finally, because evolution is an ongoing process, typically in response to environmental conditions, some mutations simply haven't yet been weeded out of our genomes.
How does knowing our evolutionary history advance biomedical research?
Because we and other organisms share common ancestors, our basic biology is similar. This means that researchers can learn about our biology by studying mice, fruit flies and even single-celled creatures that share part of our evolutionary history. Findings made in these and other so-called model organisms have taught us a tremendous amount about cell division, gene expression, embryonic development, metabolism and other fundamental processes that contribute to our health.
Can understanding evolution improve our health?
Studying evolution not only helps us understand why we're healthy, it can help us stay that way by guiding the development of approaches to prevent and treat many different types of diseases. For example, knowledge of bacterial evolution has led to the creation of a technique for tracking down the source of a foodborne illness outbreak. Learning how bacteria and viruses evolve can point to potential weaknesses that can be targeted in designing new drugs and vaccines. By understanding how our gut microorganisms adjust to the foods we eat and the medicines we take, we can explore new ways to promote the microbes' beneficial roles and reduce any harmful ones. Finally, studying the evolution of certain adaptations can help us understand how chronic conditions like diabetes and cardiovascular disease arise and persist, as well as identify ways to overcome them.
Also in this series: