One of the most important scientific theories to emerge in the mid 19th Century was the theory of evolution by natural selection, which is usually attributed to Charles Darwin, although Alfred Russel Wallace also played an important part in its development. The basic idea of evolution is that living organisms change over successive generations, mainly through random mutations in the copying of the genetic code. If some of these changes create an advantage to that organism in terms of its ability to survive, then those mutated organisms will become more numerous compared to the ones whose mutations have led to no advantage.
For some reason, particularly in the USA, there seems to be a lot of controversy about the teaching of evolution. Opponents, usually motivated by religion, argue that evolution is just a theory, and therefore should not be taught in science classes. Or, if it is, that alongside it should be taught the idea of “intelligent design”, the idea that the change in species is driven by a Creator. Of course evolution is a theory, but it is a theory with a lot of supporting evidence. That is why it is the best theory we have to explain the diversity of life on Earth, and the way that, even within a given species, different characteristics can arise in adaptation to differing environments.
With that by way of an introduction, I heard this story recently on the radio and thought it was pretty interesting, so I hunted down an article about it to share here.
Scientists in the USA have found that cockroaches have actually reorganised their taste receptors so that they now find the glucose used to coat poisoned bait to taste bitter.
According to the story, scientists noticed about 20 years ago that cockroaches were starting to avoid the glucose covered bait, which of course was leading to our methods to kill them proving to be less and less effective. This was believed to be due to a reduction in the cockroaches’ sensitivity to the glucose, essentially meaning they were finding the glucose less attractive and hence were not so attracted to the sweet bait.
But what scientists have now found is far more interesting. The cockroaches’ taste receptors (their equivalent to our taste buds) have actually been re-wired so that the receptor which used to tell the cockroach it was tasting something sweet and pleasant now tells the cockroach that it is tasting something bitter and undesirable! As a consequence they actually recoil with displeasure when they taste the glucose covering the poisoned bate!
As Dr. Elli Leadbeater says in the article
Usually natural selection makes animals more or less sensitive to certain tastes….
…In the cockroach case, sugar actually tastes bitter – an effective way for natural selection to quickly produce cockroaches that won’t accept the sugar baits that hide poision.
So the next time you are cursing the fact that cockroaches and other pests seem to be more immune to the poisons we use to kill them than they used to be, blame evolution!