Let's talk about the men who produced the story and screenplay for Space Seed.
The story was by Carey Wilber, who wrote for dozens of television series from the 1950s through the 1980s, and a decent mix of drama, action, western and science fiction.
Wilber received credit on the script that was written by long-time TOS producer/writer, Gene Coon. Coon was the showrunner for TOS until Bread and Circues. After that, and numerous disagreements with Roddenberry (Coon is sometimes called "The Forgotten Gene"), he passed that on to John Meredyth Lucas. (Apparently as he was leaving, and upset with the change in tone of the show, Coon said to Lucas, "Why the hell don't you take over? You produced The Fugitive
and Ben Casey
and that shite."
But, before he left, Coon gave us 8 pretty good TOS scripts -
"A Taste of Armageddon" (with Robert Hamner)
"Space Seed" (with Carey Wilber)
"The Devil in the Dark"
"Errand of Mercy"
"Bread and Circuses" (with Gene Roddenberry)
"A Piece of the Action" (with David P. Harmon)
...and roughly 1/2 of the TOS run, overall, as producer/showrunner (some would say the "good" half). It should be noted that Roddenberry often referred to TOS as "Wagon Train to the stars" and Coon was a veteran writer of Wagon Train
He died of cancer in 1973 at the age of 49.
Cheers to probably the best script by "The Forgotten Gene" and the man himself. Image: http://images2.wikia.nocookie.net/__cb20090427191806/memoryalpha/en/images/thumb/3/37/Gene_Coon.jpg/180px-Gene_Coon.jpg