About altitude sickness. According to wikipedia:
I took the liberty to check Greece and Italy for their highest mountains. They had a few above that height. The reason I checked those two countries is because ancient Greece and the Roman empire has had a huge impact on the world, and both are older then 1400 years. If they knew about altitude sickness, its likely it was known throughout the world.It commonly occurs above 2,400 metres (8,000 feet)