> Is Apocalypto anything like Danny Elfman's Planet of the Apes?

Not really, no. Both scores are very primordial and unsettling, but Planet of the Apes is orchestral, this is not. If you want a reference it sounds a bit like the Four Feathers meets The New World meets the action music from Braveheart. However, aside from a string figure in the first and last tracks, it really is something unique in Horner's canon. I think the closest score to this actually is Howard Shore's The Cell, since both use ethnic music to very unsettling effect. I think it's fantastic, but it's not for everybody.