To be brutally honest, whomever installed that floor is an idiot. Those who know what I'm talking about will see it right off. Looks like it was installed in sheets. Unless it is supposed to look like that, then I suppose I'm the idiot.
I'm not a pro, but my Pa was and he showed me lots of things, including how to install hardwood flooring.
We once ripped up an old gymnasium and used the hardwood to redo the upstairs (pop-top) in our house. It was a long, arduous summer.