History as social science was basically invented between 19th and 20th century. Ancient writers generally had agenda and they happily filled missing pieces with ideologically-fueled speculation.
but, intelligence is not new. There were astute readers at that time, too. So there must have been a spectrum, and reading people knew something about that spectrum.. from fawning sycophants of the current despot, to tellers of tall tales, to scholars, and those close to traders and travelers.