Why believe in evolution? Only 40% of Americans do and yet there is so much evidence to support the theory. The theory of Evolution states that we all evolved from a common ancestor and that changes in our population genetics over time has led to speciation.
The fact that we share 98.6% of our DNA with chimpanzees and 85% with mice, is proof of a common ancestor, and proof we are more closely related to chimps than mice.
We have directly observed evolution in our lifetimes, in a year, the resistance of mosquitoes DDT went from 95% being killed to only 49% being affected, they had evolved over generations, if seeing is believing then what more could you ask for?
From Crash Course: Biology on YouTube by Hank Green.