We often hear much made of the Great American Interchange, where North and South America colllided and species from previously separated ecosystems became intermingled. This makes sense - it was a dramatic story, it happened recently (so we have lots of evidence for it), and it involves lots of our favorite charismatic megafauna. Sabertooth cats, mammoths, giant sloths, and car-sized armadillos with mace-like tails. The Interchange also answers some questions - where did strange creatures like armadillos, sloths, and anteaters come from, not to mention a marsupial like the opossum? Where did llamas and jaguars come from?
Other interchanges don’t get nearly as much attention (aside from, perhaps, the crossing from Asia to North America, which features heavily in our own story). But there’s another Interchange that I find fascinating. It also saw an order of mammals that had evolved in isolation thrust into the larger world - an order whose few surviving members are quite weird and wonderful, and exceedingly varied. I am speaking of course of Africa.
So what was a pre-interchange Africa like? What did afrotheres look like 20 million years ago, and what did an eentire ecosystem dominated by them look like? And is there any media that explores this era?
Proboscideans (elephants, mammoths, mastodons) evolved in Africa and moved to Asia after the collision. Later, some of them moved to North America.
Felidae (cats) evolved in Asia and moved to other continents in multiple waves. Wikipedia says that Pseudaelurus (Pseudaelurus - Wikipedia) moved to Africa about the time of the collision.
BTW, there were other notable exchanges between Asia and N America. Wolves went east and horses went west, to give the two best known examples.
As I understand it, wolves went west and then east. The first canines evolved in North America, and coyotes are the descendants of those canines who never left. But in an earlier land bridge, some of those canines crossed into Asia, and while in Asia evolved to be somewhat larger wolves. And then the larger wolves (some of which had by then been domesticated) came back to North America, at the same time that humans did.
So did camels (who originated in North America but made it to both South America and Asia/Africa); as noted by Chronos canids appear to have done some back and forth; bears came from Eurasia and reached both Americas.
Primates skipped the whole interchange deal, evplving in Eurasia but colonizing Africa while it was still and island, and South America from there.
I’m more interested in proto-Africa and what it was like, though. We know Afrotheria was widespread - are there whole swathes of Afrothere diversity that are gone now, or was it mostly relatives of modern kinds of animals filling in various niches?
From what I can tell, you had elephant-like beasts of varying sizes, some with large trunks and tusks (though not as large as more modern elephants) and some without.
Apparently there were hyaenodonts in Africa by this time? How is this possible if Africa was separated from Europe where they evolved?
Same goes for hippo ancestors. I guess the gap from Europe to Asia was manageable even for somewhat larger animals? Primates on vegetation rafts make sense, but I have a hard time understanding how hippos and hyaenas made the journey.
Rodents made it as well but like with monkeys, I get that.
You also had rhino-sized hyraxes, hippos with horns, and afrothere carnivores without much modern analogue.
That list of critters comes from a browse of Wikipedia, but I’m wondering where I can learn more about this fascinating period.
I have read that horses evolved in North America, then went to Asia and, eventually Europe and, meantime went extinct here until reintroduced after Columbus.