Mutation

SD, you might want a peek at
Understanding Evolution - Your one-stop source for information on evolutionHigh-school level stuff, and I'm sure there is plenty there on the role of mutations.

Milagros - mutations can be, and frequently are, changes in DNA that lead to no change in the amino acid that is coded for. Thus, they are "invisible" as far as the organism is concerned: only DNA sequencing can detect them.

A few that have shown up on this very forum before:
* two different mutations, one African and one West European, that appear to give near-immunity to AIDS
* a mutation in Italians in a village that make the mutants nearly immune to high-cholesterol problems
* a cluster of mutations which allow adults to continue to digest lactose and thereby drink milk
* the hemoglobin C mutation, which, like sickle-cell, give resistance to malaria, but which usually is otherwise symptomless.

Here's the error in this analogy: I don't have to win the lottery three times. Somebody here in the state does, in fact, win it nearly every week. If they don't piss all of that loot away, they pass some of the benefit on to their kids.A single organism doesn't need to "win" three times, or even once: it just has to leave progeny that wins, say, once in a thousand generations in order to pass down noticeable change. Our state lottery used to say, "$4 million ain't chicken feed!" Likewise, a lot can happen in a million years, and we know of nearly 500 millions of years just since the first vertebrates.

500,000,000 years is a "short time period"?
Wow.
Figure out what 500,000,000 seconds is in more manageable units, and then tell me again that 500,000,000 years isn't much time.