In Gulliver's final voyage to the land of Houyhnhnm, Gulliver meets the Houyhnhnms who are horse-like in appearance but with better manners than most people. The other species that Gulliver meets in Houyhnhnm is the Yahoos: so called because they are cruel and nasty, and to Gulliver's horror, they look exactly like humans.
And so, after almost seventeen years at sea, Gulliver returns home to England preferring the company of horses to that of humans.
Although Gulliver's Travels is seen as a children's book, it is also a book about the politics of its time. Jonathan Swift wrote Gulliver's Travels with the ambition "to mend the world".