Can cheetahs outrun their own genes?
You might know that cheetahs can run 70 miles per hour, but did you know that their hips and shoulders actually swivel on their flexible spine to stretch out their stride? And did you know that their beautiful spotted fur is as soft and smooth as Astroturf? Yup. That’s just one of the reasons why leopard skin is all the rage, but cheetah fur has yet to debut on the catwalk.
And how ’bout this: did you know that cheetahs aren’t doing so well-there are fewer and fewer of them. In fact, Scientists estimate that there are between 12,000 and 15,000 cheetahs in Africa today-that’s down from 100,000 across Asia and Africa just a hundred years ago.
This isn’t the first time cheetahs have gone through tough times. At the end of the last Ice Age-close to 10,000 years ago-three quarters of all mammals in North America died off (similar extinctions happened in Europe and Australia close to 40,000 years ago). This is called the Pleistocene-Holocene Extinction event, and researchers believe that cheetahs barely survived (unlike woolly mammoths and saber-toothed tigers that went extinct).
At one point in time, cheetahs ranged across North America, Europe, Asia and Africa. After the P-H Extinction event, the only ones left were in Africa and parts of Asia. Because so many cheetahs died off, the genetic diversity of cheetahs worldwide was reduced to the genes of only a few. This is referred to as a “genetic bottleneck,” where only the genes of a small number of individuals are passed on to the next generation. (Think of a big bottle filled with marbles. When the bottle is turned upside-down, only a few marbles make it out of the narrow neck.)
What is genetic diversity? It is a measure of how many different versions of the same gene exist in a population (just think of hair color and skin color for example). Not only can these different versions result in dramatically different physical appearance (like in the case of albinos), but they can account for differences between fast and slow metabolisms or even resistance to certain diseases as well. For instance, humans with two normal copies of the hemoglobin (red blood cell) gene are susceptible to malaria, whereas those with one normal copy and one “sickle” version of the gene are immune to the disease. Those unfortunate enough to have two copies of the “sickle” version of the gene often die of another disease called Sickle Cell Anemia.
A healthy population includes many versions of different genes (high diversity), which helps to ensure that some individuals of the species can adapt to new conditions. If a particular version imparts a benefit to an individual, he or she will have a better chance of surviving than other individuals with other versions of the gene. They will then be more likely to pass on that version to future generations. That’s how evolution works.
So when a population loses its genetic diversity it becomes increasingly vulnerable to change because all of the individuals have the same versions of genes. If a new disease crops up in a population with low genetic diversity, the chances that a particular version will be able to save the day are not good. So while modern-day cheetahs aren’t facing immediate threats (other than the standard habitat loss and random poaching events), they are one bad disease or one climate shift away from extinction, thanks to their low genetic diversity.