In my world, humans didn't realize there was life beyond Earth until they discovered the Charon Relay and started traveling the galaxy. In... six years from now, actually. 2157. The Turians got mad at them for being nosy. I'm Quarian, they didn't discover we existed until later than that, since we're on the edge of the galaxy rather than a big part of the Council.
Everyone does the borrowing thing. Hell, our ship was based off a ship originally made by Turians and then the bosh'tet Illusive Man copied it. ... but she's too pretty for me to complain.