Kerbal
Kerbals (possible Latin name - Kerbious sapiens amplus capitatus, "wise large headed kerbal") are the native denizens of the planet Kerbin. Kerbals appear to be bipedal primates. Mature kerbals range from 0.5 - 0.75 meters in height.
Kerbals have a massive head with respect to their bodies, being nearly 50% of an adult kerbal's body mass. This massive head and relatively small body likely means that more energy is devoted to the head, making kerbals capable of incredible feats of logic and scientific reasoning.
Diet
The greenish coloring of kerbal skin may not only be due to environmental or evolutionary factors but, also to massive amounts of green food coloring.
War
Unknown Similar to Human warfare based on limited observation of Kerbal technology.
Material culture and technology
Limited observation makes this difficult to determine. Kerbal technology and architecture appears to share many similarities with the modernized nations of Earth during the 1960-70's.