Many changes in humans and in earth both take time to show up.
Explanation:
When earth came into its existence it was not in of today's condition. It takes millions of years to shape and form to look like now. Go through a very slow evolution human being has come into existence. Geophysicist and astronauts suggested that earth was in a form of fire ball. It was revolved in the space very fast and suddenly get detached from ring of fire and cooled down took the form of a planet.
Likewise humans also undergone many evolution. Humans were not used to stand on two feet. They crawled like baby. Thereafter, evolution of species and today's homo sapiens came into existence.
