Posts Tagged ‘evolution’

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”.)

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Form Equals Form Equals Function

Why is it that the most enduring, recognized form for aliens to take in our stories is “humanoid”? Walking upright, two legs, two arms, two eyes, etc. The most stereotypical term to refer to visiting aliens is “little green men“. Why do we so often assume that aliens will be so similar to us?

Part of it is undoubtedly because there is a comfort in familiarity; if they look kind of like us, they must be like us, right? (Conversely, we feel more confident when the bad, violent aliens look nothing like us.) A certain lack of imagination on the part of those who craft the stories also plays a role. And let’s not discount the practicality of putting a human actor in a roughly human-shaped costume.

But there’s actually a reasonable scientific justification for an alien life form to have a similar form to ours. It’s called convergent evolution.
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