FWIW, the etymology of 'human' links back to the old French 'humain(e)', the 'man' bit having nothing to do with man... it's actually the 'hum' bit that is the male part (cf 'homo') and the 'ain(e)' bit comes from the suffix '-anus' (fnarr, fnarr) as in 'humanus'.
Re actress/actor - because the sexist nature of society meant that an actress was looked down at as being a 'lesser calling' than an actor.
If you read up on the contortions that French people go through because of the ridiculous gendered language trap (e.g. 'madame le maire', because a 'maire' is masculine, but women are allowed to be mayors too), you'd be very grateful that most English is ungendered.