Simplify the following text for a Grade 11 native English-speaking person.
Original: Many of those whom subsequent centuries term evolutionary biologists read him , notably Charles Darwin and Alfred Russel Wallace , for each of whom Malthusianism became an intellectual stepping-stone to the idea of natural selection .
Simplified: Many evolutionary biologists read him , especially Charles Darwin and Alfred Russel Wallace . For both of them , Malthusianism became a stepping-stone to the idea of natural selection .