What if?...Island California?

What if California, including Baja California, had broken completely off of North America back in say the Eocene or Oligocene. It heads south and west a little bit, carrying a full range of North American mammals of the era with it. That would include Tarsier and Lemur-type primitive primates, primitive carnivores like Creodonts, the extinct North American branch of the marsupials, lots of unique herbivores, and maybe even some real exotics like land-going crocodiles, the primitive rodent-like (and possibly egg-laying) Multituberculates, and a side-branch of the primates which developed rodent-type teeth.


It provides a Madagascar-style refuge for those primates, along with other North American mammals of the era. The primates develop into a full ecological range, sort of like the lemurs of Madagascar. You could have all kinds of unique animals, given millions of years and a fairly large island like that. Again, there would be an upper limit to the size of the animals that could survive, especially carnivores. The animals would survive in isolation until Indians developed good watercraft, or until the Polynesians discovered and colonized the island.

I'm not sure which would happen first, but whenever humans landed, they would wipe out the larger and more exotic mammals. I'm not sure whether that should happen early or late. Early--as in 20,000+ year isn't as plausible, but it opens up some interesting possibilities in terms of a very primitive human society surviving there.
The ice age would reduce the ocean distance to be covered, and one minority school of thought says that the first wave of people to North America were ocean-oriented and came in along the coast twenty to thirty thousand years ago. I suppose I could buy into that school of thought, then add in a chain of intermediate islands that are available as stepping stones during the ice ages and are submerged when the glaciers melt. That could give us a human society essentially totally isolated for over 20,000 years. That could make for some interesting genetic impacts and probably for some interesting social consequences. I can't think of any human group that has been totally isolated that long. The Tasmanians were isolated for about ten thousand years.


If I go that route, I may still have Polynesians or more modern Indians discover the island, but recently enough that they wouldn't have displaced the original islanders-maybe as late as 1000 AD. That would give them time to form a colony, but not to take over the entire island. It might be better to have them visit the island but not settle. I suppose it would be possible that neither one would discover Island California. In that case the Spanish would find the island, figure out that it was inhabited by primitive savages, then ignore it or treat it as an obstacle until English privateers tried to use it as a base in the 1580's. After that it could have a really neat and colourful history, or maybe get ignored again for nearly a hundred years like Australia was after the Dutch discoveries. I haven't worked that out yet. In any case, enough animals would survive that the island might become a natural laboratory for European scientists like Darwin.


Of course there is the question of whether the Spanish or English or Darwin would really have existed given this alternative. The real, but not very fun answer to that is almost certainly no. Over forty or fifty million years, enough changes would almost certainly propagate across to Europe and Asia to make them unrecognizable. I even suspect that if humans existed they would at least be a different species than us.


If that's true, why pursue this as if unchanged Europeans could discover and interact with this island? Because it's fun and it also may give me insights into real history. There is a whole field of interesting speculations as to what might have happened if the Europeans had gone out and discovered something very different or subtly different from what they actually did. Why ignore those possibilities?

This kind of scenario gives me a great deal of freedom in terms of designing the island. I can control how much broke off-I think I'll make Island California about the size of New Guinea. I may also have a couple of smaller outlying islands which are connected to the main island during the ice ages and become isolated but not completely submerged during the interglacial periods. That would allow for some competition for island animals. New species might have time to develop during the longer periods of isolation, then they would compete with each other when the islands rejoined as the sea level went down. The islands would also be natural laboratories to look at the impact of isolation on small groups of humans.

I can control the climate of the island(s) by moving them further south or not as far south. I think I'll give them a mix of vegetation. There'll be a large area suitable for rain forests. In the north, especially in the mountains, there'll be smaller areas of temperate forests more like the California forests of our time-line. To the south, I'll add in smaller areas of savanna and even a small desert. One of the outlying islands will be mostly covered with tropical forests. The other one will be open plains with some desert.

This is one i found, which i found to be very interesting and a bizarre twist on evolution.

Thoughts and comments?