I've been studying a bit of human history recently and as many of you have probably heard, the worldwide population count increased sharply in the last century or so. link
the world's population was between 250 million and 500 million throughout the entire medieval age (500 AD to 1500 AD), so i assumed 330 million people on average (which it was around 1000 AD). 330 million people for a thousand years makes 330 billion human-years.
In the time period since 1970, approximately 6 billion people lived on earth on average, so that makes 55 * 6 billion = 330 billion human-years.
so, roughly speaking, as many human-years happened since 1970 than in the entire medieval history.
that might do a part in explaining why technological and societal progress has been so fast in the last couple of decades.
i wonder too, and i actually wanted to calculate this using a libreoffice calc table but i fell asleep halfway through and then i forgot xD i'll probably look into it some day again :D