Air Date: Week of July 18, 1997
Scientists have long thought there is only one species of elephant in Africa. But earlier this year, DNA evidence suggested African elephants may well come from two separate and distinct species. For commentator Gwen Acton, that finding is just the latest example of a thorny problem. She says the lack of a clear way to define species creates a predicament not only for scientific research, but also for conservation efforts. Commentator Gwen Acton is a biologist at Harvard University's Museum of Comparative Zoology.
CURWOOD: Scientists have long thought there is only one species of elephant in Africa. But earlier this year DNA evidence suggested otherwise. African elephants may well come from 2 separate and distinct species. For commentator Gwen Acton, that finding is just the latest example of a thorny problem. She says the lack of a clear way to define species creates a predicament not only for scientific research, but for conservation efforts as well.
ACTON: One traditional approach to defining members of species states that if animals can mate and produce fertile offspring, then they are the same species. For example, horses and donkeys can breed, but their progeny, mules, are sterile. So horses and donkeys are considered members of separate species.
A difficulty with this type of classification is that there are many organisms, such as bacteria, that reproduce without mating. A second problem is that some organisms remarkably different from each other can interbreed. For example, wolves and coyotes can produce fertile pups with each other, but they are considered different species. Not to mention that practically speaking, biologists in the field cannot make 2 animals mate, then stand around waiting to see if they produce fertile offspring. While there are a number of other attempts at defining species that incorporate various factors, such as evolutionary history and geography, the truth is that a majority of the world's organisms have been classified simply by their appearance and body structures.
But here, too, there are problems. Recent DNA work shows that many microbes which look identical to humans under a microscope may be as different from each other genetically as maple trees and starfish. And the finding that savannah and forest elephants probably have been different species for at least the last 3.6 million years comes despite decades of intense research on elephants. One can only begin to imagine how many misclassifications there are in less well-studied creatures.
While new DNA technologies are aiding in classifications, scientists must find a less ambiguous definition of species, and fast. It will be important in measuring biodiversity throughout the world. In addition, many rare animals are protected by legislation or government treaties, such as the Endangered Species Act or bans on ivory hunting, that are vulnerable to change on the basis of species classifications. Unfortunately, given the current pace of research in this area, the organisms themselves may disappear before consensus is achieved.
CURWOOD: Commentator Gwen Acton is a biologist at Harvard's Museum of Comparative Zoology.
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