Image via iStock.com/Stefan Rotter
A new book examining the evolutionary biology of city-dwelling animals has come to an interesting conclusion. Evolutionary biologist Dr. Menno Schilthuizen argues in his book, “Darwin Comes to Town: How the Urban Jungle Drives Evolution,” that in city and urban environments, the evolutionary process is occurring at a much more rapid pace than anyone expected.
According to ABC News Online of Australia, Dr. Schilthuizen explains, “But at the same time we see in cities and other manmade environments that evolution really proceeds much faster than Darwin himself thought, at that time.”
One example he uses to support his argument is the mummichog, which is a small brackish water fish that lives off the east coast of North America. Dr. Schilthuizen explains in a quote from ABC News Online, “The mummichog lives in estuaries and ports and areas that sometimes are very heavily polluted by PCBs (Polychlorinated Biphenyls), which are chemical compounds that are lethal to most fish and probably also these mummichog fish.” He goes on to explain that in a span of around 10-15 years, the mummichog has been able to adapt and thrive in the highly polluted ports.
One reason their evolutionary biology has been able to adapt so quickly is because of their shorter generation times. In other words, animals that procreate more quickly are able to go through the “survival of the fittest” process more quickly.
Dr. Schilthuizen explains, “This is sort of like evolutionary clock speed, because [with] every generation you see the effect of natural selection in the previous generation. So the shorter that time period, the faster these changes can take place.”
Dr. Schilthuizen also explains that fish are not the only animals that are adapting faster than expected. Blackbirds are also evolving and adapting to city living as well. He explains, “They have gone quite far in their evolution, including the shape of their beaks, which are shorter in cities.”
He goes on to say that the blackbird is unique because there are observable biological and behavioral differences between forest blackbirds and urban blackbirds. He says that they are seeing less and less reproduction between the two blackbird populations, which could eventually lead to separate species.
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