system
Given the following post, respond as if you're commenting on Reddit:
human
How was it possible for people to train pigeons to take messages between places?

Wouldn't they just fly away?
gpt
Carrier pigeons aren't exactly trained to take messages between places. For one thing, they only take messages one way. For another, they're more bred than trained.

A long time ago (probably around the time of the ancient Egyptians, from what historians can tell), people realized that there was something kind of special about pigeons. Most pigeons spent a lot of their time around there "home area" where their nests and their mates were. And, when they went somewhere else, they were really good at finding their way back home.

When people realized that these birds were inclined to return home and also good at it, they realized they could use these wild birds if they domesticated them. So they started selectively breeding them. They picked the birds that were the best at finding their way home and bred them so their babies would be even better at it. They also bred them to be comfortable around humans. What they ended up with is what we call a homing pigeon.

A homing pigeon can find its way home from a way further distance than a wild pigeon can, and it does it pretty much any time it's free and it's not at its home.

So what people can do is raise a bunch of homing pigeons in one place, and then anybody who might need to send messages to that place in the future could take some of the homing pigeons with them wherever they were going. They keep the pigeons in cages, and when it's time to send a message, they tie the message to the pigeon's leg and let it free. It flies home, delivering the message in the process.

So, as you see, for someone to send you a message by pigeon they need to have one of your pigeons in captivity first, because your pigeons always want to fly back to your house.

When homing pigeons are used this way they're called carrier pigeons. Homing pigeons are also used for other purposes -- pigeon racing, dove-release ceremonies, stuff like that.