Where did Hobbits come from?

[Morwen]

Hobbits are considered to have originated, if one can call it that, some time during the Third Age. Tolkien doesn't actually say that Giants are human. We tend to think that, but there's no indication that Giants are any more human than they are anything else.

Hobbits, however, are a different story. Their origin is shrouded in the mists of time, as Tolkien would say (and probably did), and they are believed to have had their start in the vales of the Anduin between the Misty mountains and Rhovanion (Mirkwood).

Off topic question - what does Tolkien actually say about Giants? They are mentioned once in "The Hobbit" but does he mention them elsewhere?

Hobbit origin
Though Hobbits first appear in records during the Third Age (TA 1050, Appendix B, LotR) Tolkien notes that they "had, in fact, lived quietly in Middle-earth for many long years before other folk became even aware of them" (LotR, Prologue). They didn't necessarily originate during the Third Age.