Don't know if you noticed this... but there's a great resemblance between Sweat and "the Old Man and the Sea" by Ernest Hemingway. Just wanted to share that with you.
Just a quick theory, it's the whole evolution thingy, with Tool, the very first song I'm the hunter and the fisherman symbolizes early man, hunter gatherer type. Then shoot straight to Lateralus which symbolizes growth, maturity and all that shit. In a sense Tool has put the history of evolution onto 4 cds over 9-10 years.