[full of spoilers, as usual]
So this section is basically a post-apocalyptic western. If Cormac McCarthy fused The Road and Blood Meridian together and decided to write the whole thing in a ridiculous made-up dialect, it might resemble "Sloosha's Crossin.'"
I'm not a particular fan of dialect (I tossed The Help aside pretty quickly because I couldn't bear the author attempting to appropriate those African-American voices). Mitchell, at least, is up to something sort of interesting with his use of dialect (annoying as it is). We're several hundred years beyond the Sonmi section at this point, long after some horrendous unspecified cataclysm known as "the Fall," and the remnants of civilization exist in various tribes. Our young hero, Zachry (the Brave!), speaks in a slangy ungrammatical fashion that is perhaps meant to suggest language evolving back into a more "civilized" form. Post-Fall civilization has forgotten its ancient gods, and now worships Sonmi (wow, she must have really Ascended!) and fears Old Georgie, a Satanic figure who will eat your soul with a spoon if you don't watch out! Most of the section concerns Zachry's relationship with a "Prescient," a group who live on an island somewhere and have preserved knowledge of the world as it once was. As Zachry says, early on, "This ain't a smilesome yarn," but despite some nasty, nasty brutality, it does work its way to an ending that's at least somewhat hopeful, seeming to reach out toward us as readers and invite us in: "Hold out your hands. Look." Presumably this is as far as we will proceed in chronological time (based on section headings) so, in a sense, we have reached not THE ending, but AN ending, reinforcing the novel's theme of interconnection and the cyclical nature of history.
Random observations and questions:
Obviously, we're meant to connect Zachry's tribe to the Moriori from the Adam Smith section (civilizations predicated on peace).
Storytelling is emphasized throughout, once again, with several stories embedded within the larger narrative, much of which (we are told) may well be unreliable (just a bunch of "musey duck fartin'").
Cloud Atlas, we know already, is a musical piece by Frobisher but it's also a description of the novel's themes: "Souls cross the skies o'time...like clouds crossin' skies o' the world" (302).
So what about this recurring birthmark? Are those characters all the same character, reincarnated?
I like the fact that Zachry's culture uses "horny" as a verb and a noun at various times: "We'd got a feverish horny'n for each other, see...". I will be employing this grammatical structure in my own vocabulary.