Sutcliffe was a Human man. He was a member of Starfleet.

In 2364, in a timeline altered by Q, Sutcliffe and Miles O'Brien were puzzled when Jean-Luc Picard ordered the crew to red alert. Sutcliffe thought the decision a stupid one, but O’Brien defended Picard. (TNG novelization: All Good Things)

Appendices

Background information

Sutcliffe was named after Stuart Sutcliffe, who left the Beatles before the height of their fame. In an early draft of the episode, Sutcliffe requests a transfer off the ship. (TNG Companion, page 301)