Fulson Miller was considered a genius when he completed his doctorate by the age of 16, signing up to join Starfleet seemed a no brainer however he was surprised to find his lack of what some would describe as common sense held him back. Despite feeling he was ready it took him a further 3 years to be accepted to the academy.
When he finally arrived he moved through the curriculum at a rate of knots completing many modules of study far in advance of when they were needed. Noticing how quickly he was churning through Starfleet Academy the Admiral in charge reached out to other areas of Starfleet to see if there was something they could give Fulson to keep him busy. Utopia Planitia answered the call, for the next 2 years they took Fulson as a cadet and had him get involved in several ongoing projects they needed his brain for.
When he returned to Starfleet Academy he did so with two admirals commendations, whenever the Starfleet Comendant tried to find out what these commendations were for he found himself blocked by layers of Starfleet bureaucracy. Despite this those commendations went a long way to helping Fulson complete the academy and attain the rank of Ensign.
Unfortunately for Fulson both his incredible lack of ability to act human, and the knowledge swimming around in his brain means he is unlikely to ever advance beyond the rank of Ensign. As one of his fitness reports said he is a man who knows just enough about everything to get himself killed twice when once would do the job.
When the position of Chief Engineer aboard the USS Aquarius came up his name was put forward by Starfleet Command as it provided a relatively safe position for Fulson to occupy whilst he learned how to sink or swim as a Starfleet Officer. The knowledge he possesses about Aquarius’ core systems comes as a boon too as he was involved in several elements of the research and development that went into the ship.