The Kismet modification was a genetic modification that was supposed to make humans more suitable for life on a high-gravity planet in the Kismet System.
Charles Townsend and his parents possessed the modification, which resulted in a stout build and great physical strength, but also required a larger-than-average food intake due to the super-active metabolism. (MA1)
It was one of the modifications Allison Benton-Ramirez y Chou suspected Alfred Harrington might have – he actually had the Meyerdahl First Wave. (HHA6.3: BATB)