Simplify the following text for a Grade 9 native English-speaking person.
Original: Richard Wrangham of Harvard University argues that cooking of plant foods may have triggered brain expansion by allowing complex carbohydrates in starchy foods to become more digestible and in effect allow humans to absorb more calories .
Simplified: Richard Wrangham of Harvard University argues that cooking of plant foods may have caused the brain to get bigger , because it made complex carbohydrates in starchy foods easier to digest . This made humans absorb more calories .