The Panama straights

WI North and South America had stayed divided by sea. One effect would probably be that at least until humans crossed the straits South America would have marsupials as the dominant mammal order.

I guess plant species might also be different.

How much of a Political difference would it now make?

There would have to be a very large gap to give South America completely different fauna; at the very least, rodents could swim the straits.

Some placentals made across the island chain before the Isthmus of Panama formed, but the main waves camme afterwards. Ironically, humans would probably have crossed easily, as they did to Australia. Also probably, with similar results to the native fauna.

Any changes to climates from changed ocean currents would depend on the width and depth of the straights. I recently read one argument that the crosing of the former straights caused. or at least helped, start the Pleistocene (Ice Age).

the Mayan were a ocean [or at least sea] going people, If they had been able to sail up or down the west coast....

If whe still have the Spainish take it, Whe wil not have the Straits of Magellan, or the Dutch seeking to by pass it, finding Cape Horn. the Patagonians may survive, longer.

We humans are very persistent. A strait would not stop or even considerably slow down our expansion into South America.

mortifiedpenguin said:

We humans are very persistent. A strait would not stop or even considerably slow down our expansion into South America.

Click to expand...

I would tend to agree with that.

Where it gets interesting is, as DQ said, when you factor in a greater opportunity for sea travel among the native states. What kind of technological leaps could they have made if they had the impetus to develop sea-worthy vessels?
Then you have to take into account the differing migration patterns into SA caused by a strait - what kind of empires arise there? Are there still Chimu, Inca, Aymara, or similar states, or something completely different?

And again like DQ said, think about how New World colonization is going to proceed with such a nice convenient passage to the Pacific. It's quickly going to become one of (if not THE) most hotly-contested piece of real estate in the world. All European colonization drives will focus on that area, and only when some power finally has an unshakeable claim and control of it, will colonization expand north and south, although certainly there will probably be small 'starter' colonies in other locations in the Americas.