Evolution as a real-time phenomenon
December 1st 2007 13:09
Many people harbour the misconception that evolution is something that only happened in the very distant past, and that it can only be discerned from evidence pointing to its ancient occurrence. While there is much truth to the notion that evolution is inferential, it has actually been directly observed while it is taking place, not only in artificial breeding programs and experiments, but in observations of wild populations in which genetic and morphological changes can be tracked in real time or soon after they have taken place. The formation of incipient species can be tracked over a period of time by comparing samples from the population and looking at shifts in morphology, DNA composition, or both.
Another popular view of evolution is that it only happens extremely slowly, taking many, many generations for changes to accrue and eventually replace the previous forms (with the possible exception of antibiotic resistance in germs and antiviral resistance in viruses, which most people are somewhat familiar with). But given a strong enough selection pressure - like the one imposed by human interference in an organism's ecosystem - changes can spread through a population very quickly. This, too, has been directly observed, with many species adapting to the effects of humanity on their habitat in a host of interesting ways. This process of rapid evolution is well known in pest species, but it is increasingly been seen in native animals too, often in response to pests.
Here is a quick overview in Scientific American Magazine, December 2007, by Rob Dunn. Here is an excerpt from the article:
"Rats have developed smaller bodies when introduced to islands. Trophy fish have also adopted smaller body sizes in response to fishers’ preference for big fish (which, if killed, do not breed). Mayflies in streams where trout were released now forage at night to avoid the fast-swimming predators. Many hundreds of herbivorous species have switched to novel, sometimes toxic, food sources introduced by humans and have come to specialize in consuming those new resources. Various native species have evolved in response to newly arrived competitors. Cedar trees have begun making toxins to protect themselves from being eaten by deer now roaming in their formerly benign habitats. Mussels in New England have evolved the ability to detect invasive green crabs and produce thicker shells where the crabs are present."
Another popular view of evolution is that it only happens extremely slowly, taking many, many generations for changes to accrue and eventually replace the previous forms (with the possible exception of antibiotic resistance in germs and antiviral resistance in viruses, which most people are somewhat familiar with). But given a strong enough selection pressure - like the one imposed by human interference in an organism's ecosystem - changes can spread through a population very quickly. This, too, has been directly observed, with many species adapting to the effects of humanity on their habitat in a host of interesting ways. This process of rapid evolution is well known in pest species, but it is increasingly been seen in native animals too, often in response to pests.
Here is a quick overview in Scientific American Magazine, December 2007, by Rob Dunn. Here is an excerpt from the article:
"Rats have developed smaller bodies when introduced to islands. Trophy fish have also adopted smaller body sizes in response to fishers’ preference for big fish (which, if killed, do not breed). Mayflies in streams where trout were released now forage at night to avoid the fast-swimming predators. Many hundreds of herbivorous species have switched to novel, sometimes toxic, food sources introduced by humans and have come to specialize in consuming those new resources. Various native species have evolved in response to newly arrived competitors. Cedar trees have begun making toxins to protect themselves from being eaten by deer now roaming in their formerly benign habitats. Mussels in New England have evolved the ability to detect invasive green crabs and produce thicker shells where the crabs are present."
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