Hi there! I have no clue which Greg you're referring to, but I can give you some points on a thesis statement.
As you hopefully know, a thesis statement gives the reader a main idea of what the body paragraphs will be about. It doesn't have to be long-- usually it's one sentence and just gets straight to the point.
Here's a starter;
By the end of "(title of the story)", Greg changes into a (what he changed into) because of (idea of 1st paragraph), (idea of 2nd paragraph), and (idea of 3rd paragraph).
Hope I helped!
Answer:the expert opinion that humans have always been carnivores
Explanation: