Just so its on the record. I reserve the right to contradict myself.
Ahem....
So, if we get to the point of establishing a Macaronesian cultural/economic/sailing complex, centered around the Canary Islands as metropolis, and with the remainder of the Islands and some part of coastal Africa as a hinterland, with the most likely configuration being a former Carthage/Cadiz colony, most likely following the 2nd Punic war as either an extremely far flung minor roman province, or a roman oriented tribute state.
Well, that gives us a sailing culture which could conceivably make it to the Coast of Brazil. The big nut to crack, as I keep saying, is getting back. The return voyage is extravagantly difficult and improbable, and almost certainly not economic.
Is there any way we can push this a little bit further? If economics don't work, what about cultural factors?
One thing that strikes me that might be at work, particularly during and lingering after the discovery phase, is 'gamblers fever.' I'm sure that there's another term for it - intermittent reinforcement. The fact that a chance pays off once in a while, or might pay off persuades people to keep playing. This is why people buy lottery tickets or throw their life savings away at a casino (well, there's also the doubling down phenomena - basically, when someone's made the mistake of throwing a lot of money down the well there's a strong impulse to keep throwing down money, otherwise you have to admit that all your time and money and effort up to that time has been for nothing).
So the continuing discovery of a handful of Macaronesian archipelagos, about 30 islands, and the potential wealth that comes from a virgin new Coffee Island probably inspires a lot of fortune seekers.
There's soothsayers giving the locations of new Islands and new fortunes, smugglers and pirates claiming that their coffee comes from previously unknown and still mysterious islands, learned men of letters proving to each other that there must be more islands out there. There's dreams, dreamers and half ass lunkheads. There's the desperate, gambling on that incredibly long shot. The ambitious seeking to make their fortune, etc.
So, during the period of exploration, they keep setting out to sea... and it works to some extent, they find the Azores and Cape Verdes.
Mostly, they just die at sea. They die a lot. Their ships founder in bad weather, they spring a leak and sink, the crew mutinies, they get lost. Basically, they die in profusion, in numbers. Many of the ships that go out don't come back. Of those that do, many come back empty handed. And a favoured few, the ones who find the Azores or Cape Verdes, might come back with something. But after that, it's a lot of dying at sea or coming back busted.
Now under those circumstances, I expect two things to happen.
Some of those who don't come back will make it to the coast of Brazil. The currents are right, the winds are right, and presumably they've brought a modicum of skill and preparation. And mostly, they die there. It's really really hard to get back.
I suppose that there's some possibility of a Phoenician settler colony composed of stranded sailors, that merges with the locals. It might last fifty or a hundred years, unless its very lucky. But I'm not going to worry about that for now.
The second thing is that the seamen who come back empty handed will come back rich in knowledge. Mostly that knowledge will be that spending three weeks bopping around the empty ocean really sucks. But there'll be a modicum of accumulated awareness of winds and currents. So it's likely that they'll figure out the Volta, and perhaps develop that as an institutional knowledge - ie, the traditions and insights that everyone defaults too.
At that point, late, very late in the age of exploration and consolidation, you might have, a really gifted and unlucky fool who ends up in Brazil, and in one of those 'Incredible Voyages' which we usually associate with team ups of wily cats and broken down dogs travelling thousands of miles to find their absent minded owners, he has the combination of hunch, competence and foolhardiness to assume that there's a way to get back into the Volta and get home... all he has to do is follow the coast far enough north...
Aaaand..... he makes it home.
Aaaaaannndddd..... nothing comes of it. It's like the circumnavigation of Africa, or putting a man on the moon. Impressive, dramatic, thought provoking, awesome... and futile.
Now, I imagine anyone who makes a journey like this is going to talk it up the wazzoo, so the stories will be amazing and epic and all that, extravagant as hell.
But he's probably not come back with his cargo hold full of trade goods. That's not sensible. Sailing in unknown territory, crossing indefinite expanses of water. Priority will go to provisions for survival, not booty to impress the hometown folk. You want to get there alive, not die in the middle of the atlantic with a hold full of gold.
There's probably a few barrels of trinkets, perhaps a small supply of chocolate as proof, things like that. But not big.
There might be some talk about more voyages, now that it's been done. The second time is easier. And there might even be visions of wealth - gold and silver, chocolate or tobacco or coca leaves as hot commodity, perhaps the rumour that the far land is the source of coffee and there's a bonanza waiting to be claimed.
And at that point, it should go nowhere. The talk will be just talk. No matter how much hypothetical wealth is out there, the difficulties of getting it back, and the exponential costs of setting up a trade network would be outside the economic capacity of the Canary metropolis. There's just not enough wealth to make that kind of investment and no real motivation to do so. In particular, the Canary metropolis might want to have a whole new supply of coffee... but on the other hand, it doesn't want competitors, or the price to collapse.
The only state that might have the resources to set up such a trade network - including posts and resupply stations, would be Rome. And there's no military or political reason to do so. It's certainly not a paying proposition. So what it comes down to is boondoggle, the senseless whim of a some crazed emperor, pouring the wealth of the state into such a venture. You'd need a lot of money, a lot of wealth and input, for very little to show for it. So the only reason it would happen would be misinformation, skewed assessments, really bad decision making and an immense fortune disposed of recklessly.
So you could, hypothetically see a Roman presence and a series of Roman outposts, way stations, trading stations and resupply depots from the coast of Brazil to the Caribbean and beyond, established and maintained at ruinous expense, so some goof of an emperor can impress his friends with chocolate malt.
That will probably last until the change of Emperors.
And its unlikely to have much of a meaningful effect. After all, Rome and China knew of each other, and there was some limited exchange through the silk road. There was some contact between Meso-American and Andean cultures. But in each case, the contact was mostly insignificant. This would be the same... only more so.
Archeologists would find a few roman trade goods in American sites. But that's about it.
I give the Achaemenid Persians and the Kushans props for being probably the most cosmopolitan cultures of the ancient world.
