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Have opossums stumbled upon the Fountain of Youth?
Kaelin Callow and Lauren Eekhoff
This article was based on the paper titled “Retarded senescence in an insular population of Virginia opossums (didelphis virginiana),” written by Steven N. Austad who is affiliated with Harvard University’s Department of Organismic & Evolutionary Biology. It was published in The Zoological Society of London in 1993.
Researchers have found that populations of opossums have accomplished what no skin care routine or amount of cosmetic procedures has been able to achieve: slowed physiological aging.
Roughly thirty years ago, a Harvard professor named Steven N. Austad published a study regarding populations of opossums, and specifically their differences in aging. This study looked at two populations of opossums that were genetically isolated, meaning that they were not able to breed with one another. One population was insular, or found on an island, and the other was found on the mainland. These two opossum populations supported a fundamental theory of evolution: the evolutionary senescence theory.
The evolutionary senescence theory was an idea developed by scientists in the 1960s. Senescence, the central point of the theory, is a word that is used to describe the biological changes that take place as an organism grows older. This theory is based on the idea of natural selection, which can be defined as the natural elimination of negative traits and the natural continuation of positive traits. This happens because organisms that are more fit for their environment are more likely to reproduce and pass their traits to the next generation. The theory states that the biological effects of aging are due to the fact that after an organism is done reproducing, they may no longer pass their genes (in the form of offspring) into the next generation. For this reason, if an organism has some kind of negative trait that occurs post-reproduction, they will pass this trait to their offspring, creating a buildup of traits that lead to death later in life.
Less stress, less wrinkles?
Virginia Opossum (Didelphis virginiana); cc Liam Wolff
Because of the fewer environmental threats found in the insular populations, Austad hypothesized that these insular opossums would have adapted to a more laid back style of reproduction, taking more time to produce high quality offspring because they have the time and resources. On the other hand, mainland populations experience greater pressures, causing them to produce more numerous offspring of lower quality because this increases their likelihood of spreading their genes into the next generation. Therefore, the opossums on the island ultimately provide strong support for the idea of evolutionary senescence.
As expected, Austad found that the insular opossums had lower mortality rates and survived longer than the mainland opossums. In fact, 50% of the insular opossum population survived into a second year, and 9% into a third year; whereas only 25% of the mainland opossums survived into a second year, and no opossums survived into a third year.
As any great researcher would, Austad investigated potential variables that may have caused these differences, such as differences in climate, parasites, food shortages, and disease between the two populations; however, he determined that there were no environmental differences between the two groups of opossums in any of these categories; therefore, he concluded natural selection has led opossums to adapt to their environments. By surviving longer, insular opossums support the evolutionary theory of senescence. Do these small creatures serve as proof that the secret to continued youth is escaping all your troubles and moving to a private island paradise?
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