KATHMANDU: The theory of evolution is overshadowed by various misconceptions, making it one of the most controversial among various scientific theories. Ever since the dawn of early days, the theory has been difficult to comprehend even though the facts present a diversity of beautifully painted evidences on a perfect canvas of nature.
Scientists and philosophers have wondered about the vast diversity of plants and animals around us from the beginning of ‘human understanding’. But it took one scientist to connect the dots, and it did not come easy. It took him daunting circumnavigation, all the way to South America and surrounding islands, especially the Galapagos. That person to was Charles Robert Darwin, born 211 years ago on this very day. His voyage of the HMS beagle changed the course of human understanding and scientific realms. It was in those islands where the poetry of Evolutionary history unfolded in Darwin’s beautiful mind.
Before getting into what Darwinism is, I think I need to layout ideas of evolution. Evolution is a gradual change in different characteristics of a species over a long period of time. The long period of time portion comes in handy when explaining the theory of evolution. One question that you constantly face is, why can’t we see evolution happening in front of us? The answer to that, however is – we can! I’ll get to that part later.
Let’s get Darwinism rolling
The key component of Darwin’s theory of Evolution is Natural selection, often termed as Evolution by natural selection. In the simplest of context natural selection is the process whereby the “fittest” (to be defined later) survive and reproduce while the unfit ones die out. We’ve all heard about “Survival of the fittest” or “Struggle for existence”. Both of these things interplay in the game of survival which basically ensures reproduction.
Let’s dive into an example of natural selection.
The idea of Evolution by natural selection was not well received during Darwin’s time, neither did it cope well after his death. But at the peak of the industrial revolution, something happened that kind of helped Darwin’s idea of evolution by natural selection resurface on the scientific world. A lighter color version of a moth called the Peppered Moth (White) (Biston betularia) was prominent in the area before the onset of industrial revolution. The moths used the white lichens on the barks of trees for shelter and camouflage. But with increasing air pollution, the lichens died, and exposed the white version of the moth against the dark background of the tree. Shortly after the plunge in the white moth’s population, a darker version of moth, Black peppered moth started appearing in the area. Eventually the white peppered moths were replaced by black peppered moths, almost 98% of moths were black during 1895. White version of the peppered moths in a dark background on the tree bark were easy prey for the birds or other predators. Hence they got selected against and weren’t “fit” for that particular habitat. Later on when the pollution decreased in the area, the white peppered moth resurfaced again. This is a perfect example of how natural selection works.
There are numerous examples of such selections occuring in nature and among us. A classical example in respect to Darwin’s finding would be to look at Darwin’s finches. During his voyage to the Galapagos, he saw different finches that looked similar but had different beaks. He collected tons of specimens of the birds and took them back to England. Upon further inspection and investigation, he realized that all of those birds had a common ancestor from a mainland or some island. That radiated depending upon the different type of food availability in the different islands they lived in. Depending upon what they were feeding on, they needed a special type of beak– if you have a specific beak for seeds then you’d do well on that island, but if you are a short beaked bird and if you’re in island with larger seeds, you’d not survive- meaning you won’t get to reproduce and pass down your genes. As nature selects for the more fit individual among the various individuals with different set of traits, the fit ones get sieved out.
Making sense of Evolution
One more example may be? There’s a fish called the Mexican blind fish which doesn’t have eyes anymore, yes! ‘Anymore’. It used to have eyes but then the fish started living in dark caves, which meant they’d rather do good without eyes, since investment in vision takes lots of energy and in places with less amount of food that could be very costly. And then, there is a member of the same fish family that lives in a river which still has eyes. Just the ones that live in the dark caves lost their eyes.
The “getting out of the species” portion takes a long time. By that I mean speciation or formation of a completely new species. Which seems far-fetched, but that’s how we have all the diversity of animals. You might have seen different types of pigeons, almost all of those pigeons came from the Rock pigeon that we see around Basantapur. Hard to believe? How about this? Cabbage, Cauliflower, Broccoli, Kale and Brussel sprouts all come from a wild variety of Mustard. Over a longer period of time people bred for specific traits and ended up with varieties of plants, all of which tie back to the wild mustard plant (Brassica oleracea). Or look at dogs, bred from a category of wolf to modern day dogs from Huskies (similar looking to wolves) versus the Dachshund, which look nothing like wolves or any dogs of bigger breed. This is a case of artificial selection by us humans, in a similar way nature selects for traits like that and ends up producing different types of animal in the long term. The question about not observing evolution happening in real time might have been partly answered by now, with the plant and dog example.
The main idea of evolution lies in the transfer of gene for that particular traits over multiple generations, which makes it impossible to see such events live in front of our eyes in real time. I
you’ve ever been asked by your doctor to complete the antibiotic dose, that is because of, you guessed it- Evolution. Ever thought about why they ask you to complete the dose? The reason is, if you start an antibiotic, which obviously doesn’t kill all the bacteria at once, by stopping the dose, you’d assist them to evolve into a resistant version of bacteria which means you’d have to get stronger version of antibiotic and at point you’d run out of choices. It’s easier to see evolution happening in microbes because of the rapid reproduction cycle.
It’s not just the microbes though, there are faster evolving vertebrates too. Some species of lizards are losing their legs at a very fast rate (in only 15 years). If they continue to lose the legs at that rate, what would they look like? So, I guess evolution of Snakes from lizards doesn’t sound too cryptic now? Similarly, the evolution of a bird from Dinosaur should feel normal too.
Evolution does make sense doesn’t it?