They are the earliest (speculators of nature, essence and existence of man and his surroundings) philosophers who had a great works in different fields of speculation about nature based on reasons. Forinstance, in sixty century BC, Socretes and Sophists, seafarers by then, discovered that there were tribes living in other parts of the world so they questioned whether their ways of living were better than those tribes vice versa. It is from here Sophists and Socrets began speculating human conduct as called 'ethos' i.e, custom or conduct and it's from here where ethics as a part of philosophy began.
But this is just the little light, for the full light, make sure you honestly do your assignment without treachery.