Originally, some of the first planets colonized were high-G rocky worlds and the settlers on those worlds were modified to handle the extreme environments. They tend to be short, stocky, but not very outgoing. As most of them were planet-based, the vast majority of colonists were wiped out during the Catastrophe. They are a close-knit bunch and are strongly motivated by revenge against the perpetrators of the Catastrophe. Sometimes derisively referred to as "landlubbers."
Colonists are very strong. They have somewhat better than average stamina, but are not very social.