The Rate of Evolution: A Well (Time) Travelled Whale

Approximately 3.7 billion years; that’s how long life has existed on Earth. Over such a long time, the appearance of life has changed drastically. Thanks to the genius of Charles Darwin, we have a pretty good idea as to why this change occurs. His theory of evolution through natural selection states that an organism will adapt to better suit its environment, enabling it to thrive and reproduce. Conversely, organisms that fail to adapt are wiped out by the changed environment. Ultimately, this gives the world a ‘survival of the fittest’ dynamic. Humans are inherently curious, often seeking to understand what life before us looked like. For me, this poses two reasonable methods: The first option is to examine fossils to determine the characteristics of life that were present in the fossil’s own time. Alternatively, you could imagine that you have a time machine at hand which can de-age life back to a desired year. I’ll opt for the latter method. A great example of a subject to place in our time machine is a whale. For the sake of ease, let’s just assume that the time machine has the required capacity. If we rewind 50 million years, what steps out of the machine might be quite surprising to most people. Picture a large dog – four well-developed legs, a long tail, fur, and sharp teeth. This animal is the Pakicetus (Greek for “Pakistan Whale”). Not what you would have expected, right? Although specific details are hard to come by, we can propose a plausible explanation for this substantial change in a whale’s development. 50 million years ago during the Eocene epoch, this creature lived on land and fed on fish and other small animals that dwelled in shallow waters. However, on land, there was more competition for food and more predators and thus more danger to the species’ survival. This explains the need to shift from land to water. As a result, over the following few million years, the invisible hand of natural selection favoured Pakicetus individuals who spent more time in aquatic environments. If we were to turn the dial on the time machine forward slightly to around 48 million years in the past, we would be looking at a crocodile-like figure with a streamlined, elongated body and webbed feet which aided in swift movement through the water. This is referred to as the Ambulocetus (“walking whale”). Its legs were also stronger than those of the Pakicetus, supporting the creature’s body both on land and in the water. Moreover, its nostrils were relocated to the top of the head for easier breathing when submerged. Just 2 million years and look how much the animal evolved! Further turning the dial to any time between 35 million years ago and today will show the modern whale. This means that all major changes that have occurred so far in the whale’s evolution happened in about 15 million years. To put that into perspective, the whale evolved from a dog-like land mammal into the whale that we know in 0.41% of the time that life has existed on Earth. Evolution occurs more rapidly than is usually appreciated – but what does this mean? With the rise of climate change, the world is changing at an exponentially increasing rate, which in turn accelerates the rate of evolution. What about humans, are we still evolving? Although it is tricky to reach a settled conclusion, the likely answer is yes. Our evolution will be partially dependent on the environmental evolution around us, and, as of now, we are encouraging this change through means like Global Warming. Genetic studies suggest that we are still evolving and will continue doing so for the foreseeable future – although humanity has an impact on our own evolution, we are still trumped by the hand of natural selection (yet again). What our evolution will look like is another matter. Will we be thinner, fatter, taller, shorter or more muscular? Will we grow an extra limb, or will we be able to breathe underwater? Currently, we don’t have the answers; only time will tell – unless someone has a time machine lying around, anyone?