In Friendship is Magic the Cakes are shown to be mixed race when Ms. Cake (in a highly human-like situation in Hospital) gives birth to a Unicorn and a Pegasus. Mr. Cakes (although there is the Cheater Cake Theory) appears to ascribe this to his own mixed-race background.

Anyone writing the Ponies as different species is writing AU whether they know it or not.

I suggest if you want to learn about Mixed-Race People in real life read Trevor Noah's Born a Crime or other such literature from South Africa, despite the Government trying its best to keep the races divided, the reality is that sometimes whites would give birth to black or colored (colored is designation of between black and white) and coloreds and blacks would sometimes give birth to white children.

So despite the Cheater Cakes Theory, Pony Race appears similar to Human Race.

7957001 But will the cake tweens be able to reproduce themselves?

What if they're like mules (a result of shipping between a horse and a donkey), being born but not being able to add to the family lineage themselves?

Maybe this is what happened between G4 and G5. Twilight spread tolerance across Equestria. The barriers were broken and ponies chose their mates among other species. The result was a near extinction of all pony species. To combat that, Twilight introduced racism back into Equestria.

7957026
Dude then Mr Cake would have never been born !

7957256 He would if cheating was involved.

7957258
Ok?

Sometimes I think people over think this show and try to apply modern human circumstances to a cartoon show meant for kids.

But what does this have to do with G5?

7957326
G5 mostly goes over the same rules as G4 despite yes some differences.

7957001
This is the reason I refer to the pony groups as races; the fact they can interbreed with no difficulty strongly suggests a common genetic ancestor.

7957384
The scariest thing I'd say. Is that there's actually a reason why the pony races are scared of each other since they have different abilities. If we can imagine them living together in peace then of course humans can.

The problem though is in real life you actually need to wait for racism to die out before you can have your multicultural utopia and I mean literally die out. Those who lived in peak racism has to age out.

7957599
And I applaud G5 for avoiding easy evangalism-the ponies clearly still hold onto their negative attitudes towards one another.

7957604
Good.