You see all these old paintings of ancient Greeks and Romans wearing robes and togas. When did pants become a thing?
EDIT: Thank you for answering my burning question. This is something the world needs to know.
I can give a bit of information about the adoption of pants in the Roman Empire. Trousers were worn by many people on the borders of the Empire and it was often considered a Gallic or Germanic custom. Over time the Romans had more interactions with these people, and sometimes they adopted their style of dress. At first this annoyed the Romans, like this incident in the first century AD:
But Caecina seemed to have left behind the Alps his cruelty and licence, and now advanced through Italy in well-disciplined order. His manner of dress the towns and colonies interpreted as a mark of haughtiness, because he addressed civilians wearing a parti-coloured cloak and breeches.
Tacitus, Histories, II.20
Later more of these people were integrated into the Empire, and they also helped to spread the fashion. While Caecina may have worn trousers because it was the best clothing for the environment beyond the Alps, by the early third century the emperor Alexander Severus apparently wore them simply because he preferred them. (Historia Augusta, Severus Alexander, 40.)
Yet pants still didn’t completely catch on. As late as the early fifth century AD the emperor Honorius forbade them in the city of Rome. They were probably popular at that time – or else Honorius wouldn’t have made his law – but there must have been some opposition to trousers.
The oldest pair of pants found in archaeology is between 3,300 and 3,000 years old. They were found in the Yanghai graveyard in China’s Tarim Basin and belonged to a nomadic horse-riding culture from that area. It differs from Ötzi the Iceman in that these are true pants. Ötzi the Iceman had a combination of a loincloth and two individual leggings that were all separate from one another.
https://www.sciencenews.org/article/first-pants-worn-horse-riders-3000-years-ago