How does Martel user the three-toed sloth to introduce one of the major these of the novel?

I think the theme here is the calm introspection that sloths seem to possess. This sense of reflection and harmony with the surroundings become a theme in the book.

I am not one given to projecting human traits and emotions onto animals, but many a time during that month in Brazil, looking up at sloths in repose, I felt I was in the presence of upside-down yogis deep in meditation or hermits deep in prayer, wise beings whose intense imaginative lives were beyond the reach of my scientific probing. ch 1