Suppose you were asked what the science of chemistry had contributed to the world. You might come up with important products such as disinfectants, herbicides, pesticides, cleansers, and shampoos. How about the contributions of pharmaceutical science? Obviously, the design and manufacture of drugs. Genetics? The ability to treat disease and improve agriculture.
But what about evolutionary science? How do people see it as being important in their daily lives? Some might propose that it helps us understand the past and where we came from: "Our place in nature" is a common phrase. But most people would be hard-pressed to come up with concrete applications that benefit us daily. Why is this the case? The simplest answer is that as scientists and teachers we aren't doing a good enough job of explaining the importance of evolution, which is one reason so many people distrust or misunderstand the importance of teaching it. Understanding some of the many ways that evolutionary science—including tree-thinking, molecular evolution, population genetics, and studies of natural and artificial selection—contributes to our individual and collective well-being is an important first step. Here are some examples.

Phylogeny, tree-thinking, and solving problems

Identifying emerging viruses

West Nile Virus
Phylogenetic analysis of the virus that appeared in New York in 1999 showed it was West Nile Virus and related to strains in the Middle East and Europe.
© AMNH

Phylogenetic trees are predictive tools. They represent the expectation that close relatives share characteristics not found in more distant relatives. If we plot similarities and differences on a tree, we have a hypothesis of how these characters change across evolutionary time. Understanding this change—whether in anatomical, behavioral, or molecular characters—has many applications. For example, studying the change in influenza genes are important for designing vaccines and tracing the spread of disease.
Trees are also useful identification tools. Typically, when an organism is discovered, scientists compare its features with those of specimens in collections to identify whether it is already known or establish it as new. For example, because genetic data on viruses, bacteria, and other microbes can be obtained quickly and compared to large sequence databases such as GenBank, DNA sequences are commonly used to identify them. As a consequence, the health sciences, forensics, and bioprospecting industries all rely on phylogenetic sequence analysis. Here are several examples of this powerful approach at work.
In the summer of 1999 a small number of elderly residents of Queens, New York, were fatally stricken by an infection that doctors initially diagnosed as St. Louis encephalitis, a mosquito-borne virus. At the same time wild crows began to die in startling numbers, along with captive birds in New York-area zoos. The two events were linked when phylogenetic analysis of the viral sequences revealed a new strain of West Nile virus, a mosquito-borne disease rarely seen outside Africa, the Middle East, and Europe. The virus circulates between birds and mosquitoes but can be transmitted to humans and other mammals. Since 1999 West Nile has spread to every state, killing small numbers of people and causing major bird mortality. Phylogenetic analysis has proved invaluable in understanding the timing and direction of spread of this disease and in providing health officials with knowledge that has lessened its impact.
Phylogenetic analysis also identified a more virulent, encephalitis-like virus in Southeast Asia that killed more than 100 Malaysians in 1998 and 1999. It turned out to be Nipah, a new virus that had jumped from pigs to humans, and more than 1 million pigs had to be slaughtered to get the disease under control. Interestingly, Nipah is closely related to—but distinct from—yet another recently discovered virus called Hendra, which likewise circulates among swine and has jumped to humans, causing a number of deaths.

Predicting outbreaks: Hantavirus

One of the best examples of the power of applied evolution is the story of a virus that cropped up in the spring of 1993, when 10 people died mysteriously in the Four Corners area of the American Southwest. The disease agent was entirely unknown, but with the help of phylogenetic analysis it was soon identified as a "new" viral strain related to Hantaviruses of the Old World. Epidemiologists (scientists who study the causes and distributions of diseases within a population) figured out that the natural viral host was deer mice, and that humans caught the disease when they breathed in dried feces and urine in old dwellings.
Subsequent analysis showed that the Hantavirus was not actually invasive, and that many Western Hemisphere rodents carry various strains of it. Phylogenetic analysis of both the rodent hosts and the viral strains revealed remarkable co-evolutionary patterns all across the Americas. This discovery is being used to identify the hosts of new outbreaks and to predict the geographic areas where new outbreaks might be expected. This research strategy is also being applied to the host-viral systems implicated in hemorrhagic fevers (a group of illnesses caused by distinct families of viruses).
Hantavirus
No one suspected that when a virulent new virus "emerged" in the American Southwest it would eventually be shown to be an old, naturally existing virus. Since then phylogenetic studies have shown it has been in the Americas probably for several million years. © AMNH

Saving people from snakebite

No other continent has as many poisonous snakes as Australia. Most are neurotoxic, and some cause many deaths each year, a good reason why developing antivenins is a high priority. Unfortunately, we know little about the venoms of many species. But since known venom properties correlate highly with a snake's evolutionary history, phylogenetic analysis can establish a predictive framework that helps identify the best antivenin in the event of a snake bite. For example, the Bardick snake and the chemical properties of its venom are poorly known, but phylogenetic analysis shows it to be closely related to the death adder. It turns out that death adder antivenin, which is easily obtainable, works against the bites of Bardick snakes as well.

Discovering species

Antivenin and snakebites
Although the relationships of Australian snakes are still insufficiently understood, current evidence indicates that related species have similar venoms. Therefore, relationships can predict the antivenenes (shown in color) that should be used following snakebite.
© AMNH
Earth's ecosystems abound with microbial life, but since most cannot be cultured in a lab environment, identifying and studying them is extremely difficult. However, the new tool of metagenomics, the study of DNA extracted from environmental samples like soils or water, offers great promise for increasing life's inventory. Metagenomic samples contain the DNA of thousands of organisms, mostly forms of bacteria. Comparing their gene sequences to those of known organisms using phylogenetic analysis often reveals new life forms.
Many of these new species are potential sources of bioproducts. Perhaps the very best example is a bacterium called Thermus aquaticus that was discovered in the thermal hot springs of Yellowstone National Park. As its name implies, it lives in near-boiling waters, which is possible because its DNA polymerase, an enzyme that helps DNA to replicate, functions at very high temperatures. Scientists went on to develop a process called polymerase chain reaction (PCR) that uses this enzyme to make millions of copies of a DNA strand (a process that requires heating the DNA) so that it can be sequenced easily. This single technology has enabled a revolution in the biomedical and genome sciences, including evolutionary biology, and has saved countless lives through diagnostic tests.
This discovery is just the tip of the iceberg. Applying phylogenetics and the principles of molecular evolution to the search for new life will almost certainly lead to numerous other discoveries with important applications across the life sciences.

Improving agriculture

Identifying Bacteria
Microbiologists are sampling environments (water, soils) by isolating and sequencing DNA. Those sequences are then compared to sequences from known species, thus allowing recognition of potentially new species. This phylogeny shows new Bacteria and Archaea (identified by "pJP") found in a Yellowstone hotsprings water sample.
© AMNH

Feeding the world's people is one of humanity's greatest challenges, and that task is becoming more difficult as the climate changes, soils are increasingly depleted, and humans continue to stress our ecological support systems. For thousands of years, as humans moved around the world, they met the challenges of changing environments by modifying domesticated crops and animals through interbreeding. Identifying the closest wild relatives of these domesticates is extremely important, for often they live in novel or marginal environments and possess genetic adaptations not found in domesticates. Interbreeding domesticates with close wild relatives interjects genetic architectures that often improve crop yields or protect from disease.
A good example is cultivated corn. Phylogenetic analysis has identified the wild relatives of corn to be the "teosintes" of Mexico and Guatemala, and has traced domestication back 9,000 years. A new species of teosinte, Zea diploperennis, found only on a single Mexican mountaintop, was discovered in the late 1970s. It turned out to be resistant to numerous pathogens that damage domesticated corn. Interbreeding Zea diploperennis with domestic corn has improved disease resistance, preventing billions of dollars of crop loss.

Evolution, invasive species, and resource management

Invasive exotic species are a major global problem. Each year the United States spends about $150 billion addressing the environmental impacts of these species, so quick identification and discovery of the origin of invasives are major priorities. A particularly nasty species, a marine green alga called Caulerpa taxifolia, escaped from an Italian aquarium around 1984 and rapidly blanketed much of the coastal Mediterranean. The native strain, found in the Caribbean, the Indo-Pacific, and the Red Sea, grows in small patches and is genetically distinct from the aquarium strain. In 2000 C. taxifolia was discovered in several bays along the southern California coast. Was it the aggressive Mediterranean strain, or the less aggressive native one? Phylogenetic analysis of DNA sequences identified it as the former, catalyzing an immediate effort to eradicate the alga.

How do we know that evolution—or any science—is important?

Try a thought experiment. Imagine that the process of accumulating scientific knowledge within a given disciple—say, evolutionary biology—had stopped 20 years ago. None of the important discoveries mentioned above would have taken place. Neither would the identity of numerous other disease agents or invasive species be known. Nor would we have discovered, described, or determined the relationships of countless beneficial organisms that are critical for many industries. We would not have knowledge derived from advances in population genetics over the past 20 years, nor would we know much about molecular evolution, which has become so central to understanding diseases, including their origins and spread.
The bottom line is that evolutionary knowledge about life on Earth affects our well-being every day, in ways perhaps less apparent but no less important than any of the other sciences. Teaching this dynamic science is crucial for understanding the history of our planet and our role in its future.
By Dr. Joel Cracraft, Curator, American Museum of Natural History
This essay was developed for the AMNH online course Evolution, part of Seminars on Science, a program of online professional development courses for educators.
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