If you cannot explain something simply, you don't understand it well enough. Baseline genetic variation coupled with environmental change cause fast adaptation via natural selection, followed by long periods of stability.
My summary of evolution:
1.) DNA is a hugely large and complex molecule. The mechanisms for copying DNA to create new cells are not perfect. Sometimes there are errors in one of the steps of duplication. When these errors result in a different strand of DNA (even if only the smallest part is affected), this is called a mutation. There are other ways that mutations can happen, such as chemical factors or radiation. When these DNA changes happen in the sex cells of an organism, they are passed to new generations. So step one of understanding how evolution actually works is to understand this constant state of change within the organism, and how it can be passed to the next generation.
2.) Genetic Variation within the species. Every individual is unique. Some crows have bigger feet than others, my penis is bigger than yours, and this is genetic. This is why we only share 99% of our DNA with each other. About that number, 99.9% of our DNA is generic human DNA, generic fish/mammal DNA, and/or vestigial DNA that simply isn't expressed anymore, or redundant DNA ensuring that even if one piece of the strand is corrupted, the cell line does not die.
You do have to understand that changes in DNA can sometimes (but not always) lead to changes in the physical traits of the individual. This is why I have blue eyes, and yours are the mud brown of the lesser human.
So there we have two examples of why there is a baseline rate of change within species. If you apply natural selection principles to this, what you would see is like Black Jesus said, a infinitely slow and gradual state of change. This would leave nice neat fossils which are all transitional between them and the species before and any species after. This is what Darwin thought, because his analogue was geological processes. Darwin was wrong here.
3.) Speciation. Speciation is the process of one species changing to another via a collection of mutations and genetic variation due to natural selection. This is the part most often ignored or least understood. I don't know why, for me this part just clicks right in. You see, this only happens when the environment changes in some way. The classic example is that you have a forest full of an extended family group of monkeys. These monkeys all share basically the same DNA except for the rare mutation here and the baseline genetic variation there. Now a volcano erupts from the ground, cutting one group of monkeys off from the other. The new group finds themself with northern exposure (africa or south america, norther exposure is the hot on), and their environment turns more arid and hot. Now, all of the variation actually has an effect. Those with long, thick, fur start to die of heat while those with short sparse hair thrive in this new environment. That idiot with the long neck (mutation) who everyone made fun of in the forest can now see further across the savannah to warn of impending lions. The NEEDS of the group change, and so natural selection CHANGES the species by selecting FOR those traits (already present within the forest group) which confer an advantage to survive.
This is also why there are not transitional species. Because Darwin was wrong. Evolution is NOT gradual. Evolution happens in a staggered way.
First the environment changes.
Second the individuals most fit to survive the new environment do, while those that aren't die.
Third, the living individuals pass on only their genes to the next generation, while those with unfavorable traits do not.
Fourth the species
adapts to their new environment, reducing the need for change, since now all the monkeys have long necks and thin hair.
Fifth, now that there is not a change in the environment, the species change reduces back to baseline, until again the environment changes.
So you see, "evolution happens" in leaps and bounds followed by long periods of stability. This is why there are no "transitional species fossils" (there are, we just usually don't realize it), because the transition only lasts a couple hundred years while the stability lasts much much longer than that (millions of years, possibly).
Ok, I'm done. I know y'all prolly trolling, but honestly I like explaining things to people so I look at this as a mental exercise more than anything. I prolly left something out, someone make sure please.
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05-09-2013, 04:31 PM
Linear Mode
