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evolution and complex organisms

From: 
Mike
Question: 

I have study about entropy, and as you say, life is not a closed system. Life does the opposite of entropy. It creates complex ordering of chemicals and store energy in such a way that it can easily be used. My question is why does evolution seem to favor complexity? in other words as evolution goes on, organism become more and more complex. We finally end up with Man. He is contentious, he has developed spoken and written languages. He can pass his knowledge on to future generations. He does if fact now probable posses all the skills to make the entire earth uninhabitable by any form of life!(nuclear war). What factors in nature would have favored the developmental of such an organism? It seems the world could have function fine without man.

Response: 

I wouldn't say that Evolution favors complexity.  Evolution only "favors" the minimum amount of work required to keep a species from going extinct.  Usually, this means adding new adaptations, rather than getting rid of old ones.  It simply takes less time and energy to progress this way.  As a result, organisms sometimes seem to become more superficially complex.

However, this is not always the case.  Look at the snake.  It began as a lizard-like creature, but its legs slowly disappeared as its body simplified.  Though snakes still have shoulders and pelvises, their bodies are superficially LESS complex than lizards.

There is no reason to assume that organisms must become more complex as they evolve.  They evolve only to prevent extinction; that is all.  For humans, this meant developing intelligence, but for bats it means developing echo-location and a good sense of smell.  Bats are just as evolved as human beings!  They have been evolving just as long as we have, and are just as modern and just as adapted to their environment.

As far as human beings destroying the world, that's certainly true, but there are plenty of other organisms which destroy the environment.  For example, beavers.  Beavers cut down trees and dam rivers.  If the beaver population were as numerous as humans, certain types of trees would almost certainly be extinct, as well as the fish which live in the rivers which had been dammed.

Another notable example comes to mind: there was a massive extinction event many millions of years ago, before the dinosaurs, where over 90% of live on Earth went extinct!  There is now enough evidence to conclude that it was the result of an over-population of single-celled life forms which emit toxic gas in small amounts.  The toxic gas built up and eventually killed almost everything on Earth!

So, humans are not the only creatures capable of destroying the planet ;)

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