You don't have to go back to pre-history, passports for individuals didn't exist in the 19th century [0]. People were free to go to other countries whenever they wanted, and they did. There were travelers and migrations all over the place. Many cultures have traditions going back millennia of showing travellers generous hospitality.
Merchants activity was often regulated, with passports for commercial activity and other customs controls. But not people. The opposite of today.
I acknowledge that there would be concerns like you mention, like violent push-back from the natives, same as there are today. Some peoples are raised in insular cultures, some are welcoming, sometimes migrations cause understandable problems, etc.
I don't think the way we do things today is optimal. We've changed things so that money is given more freedom than people. And too many people are taught that foreigners are scary.
Merchants activity was often regulated, with passports for commercial activity and other customs controls. But not people. The opposite of today.
I acknowledge that there would be concerns like you mention, like violent push-back from the natives, same as there are today. Some peoples are raised in insular cultures, some are welcoming, sometimes migrations cause understandable problems, etc.
I don't think the way we do things today is optimal. We've changed things so that money is given more freedom than people. And too many people are taught that foreigners are scary.
[0] https://www.nationalgeographic.com/travel/article/a-history-...