What you say is very true, but keep in mind, it takes on a scale of 10,000 to 30,000 years for a species to change even slightly
WRONG! It is a FACT that humans today are a good deal taller then they were in the Middle Ages. And that was only Centuries ago. Tovashi mentioned this in her post. Apparently you must have skipped over that sentence.
In Medieval times, the average human was only around 4 feet tall. These days, it is not out of the ordinary to see a 6 foot tall human.
While this change is not as dramatic as, say, growing or loosing a tail. it is still evolution none-the-less.