The Touched were a race of humans from P3X-797 affected by a disease that turned them into Neanderthals. Upon being struck with the disease, they were ultimately banished to the Land of Dark where they often lives in various groups, occasionally attacking each other.
After SG-1 and SG-3 had managed to heal everyone who was infected with the unknown disease, the affected all returned to normal. (SG1: "The Broca Divide")