How long has Portugal been in existence?

Genesis 37:18-36New Living Translation (NLT) Joseph Sold into Slavery

18 When Joseph’s brothers saw him coming, they recognized him in the distance. As he approached, they made plans to kill him. 19 “Here comes the dreamer!” they said. 20 “Come on, let’s kill him and throw him into one of these cisterns. We can tell our father, ‘A wild animal has eaten him.’ Then we’ll see what becomes of his dreams!”

21 But when Reuben heard of their scheme, he came to Joseph’s rescue. “Let’s not kill him,” he said. 22 “Why should we shed any blood? Let’s just throw him into this empty cistern here in the wilderness. Then he’ll die without our laying a hand on him.” Reuben was secretly planning to rescue Joseph and return him to his father.

23 So when Joseph arrived, his brothers ripped off the beautiful robe he was wearing. 24 Then they grabbed him and threw him into the cistern. Now the cistern was empty; there was no water in it. 25 Then, just as they were sitting down to eat, they looked up and saw a caravan of camels in the distance coming toward them. It was a group of Ishmaelite traders taking a load of gum, balm, and aromatic resin from Gilead down to Egypt.

26 Judah said to his brothers, “What will we gain by killing our brother? We’d have to cover up the crime.[a] 27 Instead of hurting him, let’s sell him to those Ishmaelite traders. After all, he is our brother—our own flesh and blood!” And his brothers agreed. 28 So when the Ishmaelites, who were Midianite traders, came by, Joseph’s brothers pulled him out of the cistern and sold him to them for twenty pieces[b] of silver. And the traders took him to Egypt.

Whether you agree with the traditional dating of Genesis or believe it to be later, I think we can both agree this predates Portugal by several centuries! And this isn't even the first reference to the slave trade, just an early, well-known example