The Betans are an offshoot of humanity from the planet Beta.
The Betan's are not so much different from humans, externally, however internally they are radically different. Thanks to the radiations of Beta's variant-G sun, its rays had produced changes in the population. Little things like tougher epidermis and depilation of body hair. According to Betan scientists, it wasn't long perhaps in a few millennia that the Betan system itself would be a closed enclave peopled by humans who had deviated too far from the basic stock to mingle with it in safely. However this trait allowed them to withstand highly level of radiations without harm.
Unlike many in the Brotherhood of Man, the Betan's didn't think that other species outside humanity were inferior, due to their own mutational background that separated them from base humans. In addition they doubted the accuracy of the test, believing it to be flawed and questioned it validity to categorize intelligent beings as animals were they possessed near-human intelligence. To keep their mutant status obscure, the Betans refrained from mixing with other humans. The Betans are renowned for their medical sciences in the Brotherhood.