comparison between early man & modern man s

 Depends how early you mean. We are less violent, on a day-to-day basis, than when we lived in a tribal setting. Our powers of communication has improved. 
As for early man living in harmony with nature, that is laughable. Early man, like other animals, ate what was around, which may have been hunted to extinction if necessary. They burned forests for wood and as a hunting technique, died young from diseases which were the result of poor hygiene and parasites, and lived a life which involved protecting your assets with violence or threats of violence. Nature was exploited as much as possible, the only difference is the scale due to our population. For example - Early Australian Aboriginals arrived and hunted the mega fauna of Australia to extinction, they brought dogs from Asia which replaced, by competition, native carnivores on the mainland, if they had the technology, they would have exploited it more. There was no thought to preserving animals so that they would breed more and be there for future generations. They seemed to be "in tune" with nature, because they were more prone to nature's whims, like cold and natural disasters. 
So the difference between early and modern man is technology. Our inherent "Human Nature" has not changed

 Early men were nature-friendly.
Modern men are destroying nature and causing pollution.

Modern men are smarter than early men

Early men were healthy and physically strong because at that time there wasn't any technological gadget that helped them to 1) travel miles just in few minutes, 2) carry heavy stuff easily and put it where it needed to be so they did all their work on their own.

 Early man, had fear in god and social norms and patterns which had to be folllowed strictly. Also he often believed that his life was predestined by god.

Modern man, doesnt believe in god, and tend to take responsibility for his life, also Modern Man is more focused on money.

 early man eat raw food like lion ,tigers but now we are eating vegetables.early man lives in caves but now we are liveing in m odenr buildings.early man wear animals skin like clothes but now we are wearing silk,cotton and wool.