Ever read Kipling's "Just So Stories"? In there is the story of how the elephant got its long nose. In brief, elephants didn't used to have long trunks. They used to have little noses until a little young elephant was tricked by a monkey to get close to a river. A crocodile popped up out of the water and grabbed the little elephant's nose. He cried out and tried keeping the croc from dragging him in the water, his mom ran over and started pulling him back harder and harder. The more she and the croc pulled, the longer and longer his nose got. Finally she pulled him free and he had this big long nose that stretched to the ground. Ever since then, elephants have had a long trunk.
This is how many people view evolution - a change happens to an individual and it is passed down from then on.
Instead, early elephants with slightly elongated trunks had a better chance of surviving and reproducing. These then produced elephants with longer trunks, which survived even better, producing elephants with even longer trunks. The genetic combination from generation to generation made for a greater chance of longer and longer trunks.
So the individual doesn't change - cutting off a dogs tail, like they do with some breeds, does not produce short tail dogs in the future. If dogs with genetically short tails (if this were a survival trait), would mate - with a greater likelihood of even shorter tails resulting.
Thus the statement individuals do not evolve, populations do.
This is an ASSUMPTION (or opinion) by those with an "E" worldview.