Evolution in Action: Corn

Evolution is one of the greatest scientific theories of all time. Note 'theory' in the previous sentence is not 'theory: I have an idea about how this works' but 'Theory: this is how it works, because we've tried to falsify it thousands of times and can't'. As a bonus, Evolution is also simple to understand.

1. Occasionally, DNA makes a mistake when it creates a copy of itself. This mistake is a small change to the genetic code that may lead to a detrimental or beneficial change in the host organism. Detrimental changes often lead to the death of the host organism. Beneficial changes may give it a slight advantage depending on the selection pressures that it faces in its environment.

2. An environment applies a variety of "selection pressures" to the organisms that live within it. These pressures are termed 'natural selection'. Some organisms have genetic variations that give them a slight advantage with respect to these pressures. Other organisms of the same species without those genetic variations have a slight disadvantage with respect to those same pressures. If this disadvantage leads to the death of those organisms before they are able to reproduce, then those organisms will die out and only the children of the organisms with the beneficial advantage will survive. At some point the entire species of the organism will consist only of the offspring of the organisms with the beneficial advantage and the species will have evolved to be well adapted to the selection pressures it faces.

I am currently conducting an experiment with evolution in my own backyard. Each Spring I am ruthlessly killing any dandelions that dare to poke their heads above the level of the grass in my yard. Ignoring for the moment that I'm not doing anything to prevent seeds of dandelions from my neighbors yards to infiltrate my yard (by, for example, being carried by the wind into my yard), my policy of killing any dandelion the moment I see it is applying a selection pressure to the dandelions in my yard that give "tall" dandelions a distinct disadvantage and "short" dandelions a distinct advantage. Note: there are a mixture of tall and short dandelions in my yard due to the fact that a random mutation of the dandelions' genetic code at some point in the past gave rise to dandelions that grow tall and dandelions that don't grow as tall. Now, the tall dandelions are facing a selection pressure that is causing them to be wiped out before they can produce any seeds. And, thus, as we now mosey into Winter, the majority of the dandelion seeds in my backyard came from the "short" dandelions.

My prediction is that in a few years time, I will have eliminated "tall" dandelions from my yard, except for the few stragglers that made it from seeds that were blown into my yard from my neighbors yards.

See how simple evolution is?

But, for a much better example, take a look at this entry from Stephen Matheson's blog entitled "They selected teosinte...and got corn. Excellent!" which provides a lot of detail on how corn, which is a type of grass believe it or not, has evolved from a grass that still exists called teosinte.

Enjoy!

Ken