What is the source of Quantum fields In the beginning of "Quantum Field Theory for the Gifted Amateur," there is the statement:

Every particle and every wave in the Universe is simply an excitation of a quantum field that is defined over all space and time.

To an naive (not gifted) self-studier, this came as quit an eye-opener. Over the course of a non-physics education, one tends to get so used to the existence of atoms, protons, electrons,etc., even subatomic particles, that it is easy to overlook where they came from.
So the above remark is a nice resolution. Then my question is, where do these quantum fields come from. 
Further, with a subsequent assertion that, e.g., all protons are perfectly alike, as mentioned on pdf page 9 of Prof. Tong's notes:
http://www.damtp.cam.ac.uk/user/tong/qft/qft.pdf
in that "there is a sea of proton stuff filling the universe," if this sea fills the universe, then where do the seas of other particles fit in - and how do they keep things straight amongst themselves.
Maybe this is too broad a question, or, more likely, I am inadequately versed in these matters. But I would appreciate any help or reference suggestions.
Thanks
 A: The "is simply an excitation" might be a bit overstated, as it if it were that simple you probably wouldn't have needed to ask this question.  It might be better stated as "can simply be modeled mathematically as an excitation".
The "fields" are part of a mathematical model that attempts to explain our observations.  Saying "where does a field come from" is a bit like saying "where does everything in the Universe come from" or "what happened before the Big Bang", which may seem intuitively sensible to humans, but are not necessarily well-founded questions.
Some "fields" may have emerged shortly after the Big Bang due to symmetry breaking, so it may be possible to unify some of the "fields" to a simpler state with fewer "fields", if that makes sense.  Evidence suggests (as well as a scientific bias toward simplicity) that the closer you get to the Big Bang, the simpler the models can be.  Unfortunately, this also makes the process of modeling things more complicated in part since we can't make direct observations of what the Universe might have looked like back then to test theory.
