We have clearly derailed far too much, so I am going to put my dick on the table and say this:
Yes, people did masturbate in ancient times, the same way the did all sorts of stuff, from raping, killing, stealing to donating to charities, helping a friend, obeying laws. The question is, did people in Prehistoric times or Ancient Rome, Egypt, Greece masturbate, on average, more than the people of today? I personally do not think so, for a few reasons:
1. Men back then, had much easier access to a pussy to insert his penis in, from the slaves he would own, the women he would fuck while pillaging enemy territories, prostitutes(back then there wasn't really any scare of STD or AIDS), as well as his wife, though according to kikepedia, in ancient Greece, the man would marry at around 30, so he had to wait a while until then, but would get a 14-16 year old wife. Also if he was truly a degenerate, and had no other hole available, he could always go for his subordinate's boypussy, but again, this would mean that he had no prostitutes available, and wasn't in any war either, or his father didn't order a prostitute to satisfy his sexual urges.
2. Men nowadays, don't have access to female slaves or war concubines and some of the things listed above can be considered rape, which isn't really a bad thing, on the other hand he has much easier access to pornography, especially on the internet. With a few clicks of a mouse he is bombarded with hundreds of pictures of videos to satisfy his sexual curiosities all from the comfort of his bedroom.
Sure, there were nude pictures in the past, but between fucking a whore without worrying about any moral or health repercussions, and jacking to some badly drawn picture, I assert that the ancient man would rather go to the whorehouse. Again, there were people who engaged in masturbation, the same way there were eunuchs or voluntary celibates, all I am saying is that masturbation wasn't as common as it nowadays, instead people would just have sex, whether it would be a sex orgies, prostitution, slave, war trophy, wife and so on.