None of these things is just like the others

In my previous post, I explored convergent evolution: when two different species, usually separated by distance, evolve a similar physical characteristic independently of each other. At the end of the post, I said that I would follow up with a post on the far more common divergent evolution.

Simply put, divergent evolution is when two groups of the same species evolve differently. The environments in which the groups live are the most common cause of divergent evolution – in other words, if two groups of the same species are separated into different environments, they will each evolve and adapt separately to fit the environment they’re in. Arguably the most famous example of divergent evolution is Darwin’s finches, which he described in On the Origin of Species:

“The inhabitants of the Cape de Verde Islands are related to those of Africa, like those of the Galapagos to America. I believe this grand fact can receive no sort of explanation on the ordinary view of independent creation; whereas on the view here maintained, it is obvious that the Galapagos Islands would be likely to receive colonists, whether by occasional means of transport or by formerly continuous land, from America; and the Cape de Verde Islands from Africa; and that such colonists would be liable to modification;—the principle of inheritance still betraying their original birthplace.”

- On the Origin of Species, Chapter XII: Geographical Distribution. Charles Darwin, 1859

The “inhabitants” Darwin refers to in the above passage are the variations of finches. (It’s interesting to note that, since Darwin was developing the very concept of evolution, he didn’t have a word for it to utilize – instead referring to it as “modification”.)

Divergent evolution can occur on both a morphological and a physiological scale. People believed that various shrimp located on either side of Panama were the same species – until the Panama Canal was opened. The groups of shrimp fought when they encountered each other, and refused to interbreed. It was discovered that although they looked the same, the groups of shrimp on either side had distinct genetic differences. It was theorized that the groups used to be part of the same group until roughly 3 million years ago, when the Isthmus of Panama rose from the ocean and separated them; they then evolved into separate species. (This is known as allopatric speciation.)

Evolution in animals is used widely in science fiction. There are countless future and near-future stories with animals very similar to, but slightly advanced from, an animal we use in present day. There are even many stories with animals that have evolved sentience and human-level intelligence (be it through natural selection or biological uplift). However, divergent evolution isn’t something we see written about much – not in animals, anyway. After all, why dwell on the differences of two groups of an animal when those same differences can be employed with regard to ourselves?

Thus, divergent evolution in humans is an extremely common trope in science fiction. There are three distinct ways this can be handled:

On-Earth: Groups of humans on Earth evolve into distinct species, each significantly different from Homo Sapien. It’s happening all around us – no reason it can’t happen to us!

Off-Earth: Humans colonize another planet or moon; they evolve in various ways to adapt to the new living environment, until there are at least two different types of humans surviving on the new world in unique ways.

On/Off-Earth: Some humans leave Earth while others remain. Humans on Earth continue to evolve, while those who left evolve to adapt to their new environment in space or on another planet. Eventually both are distinct from Homo Sapiens and from each other.

So I’m going to end this post with a fun “test”. Extrapolating from present-day, come up with one (new) idea for each of the above three types of human divergent evolution, and post them in the comments below. No re-stating something that’s already been posted either! Let’s see how many people can come up with.

Remember, this is a circumstance where we’re limited only by our imagination! The cause is usually environmental – what would a major environmental change like global warming cause? U.S. President Barack Obama stated recently that “I expect to be around to see” manned expeditions to Mars in his lifetime – how would that change us here on Earth, or the daring ones who go? There is endless potential in the ideas of what we might become!

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