Thanks -- soon the allies (or sometimes enemies) of the cavemen, the apemen, will be released as well. They are different from the 2001 style hominids we've had available for some years, and are more like a cross between a sasquatch and a gorilla. Their subtle tactics are to barrel straight across the battlefield and brain the enemy with their bare hands!
When the cavemen are opposed by THOSE guys, the headhunters are best kept tucked away in the rear of the caveman force. Better to try to squash them with the mammoth, run them over with rhino riders (which might be rather difficult) or skirmish with them with the caveman youths, and then deploy a spear phalanx of the married adults to (hopefully) resist their depleted charge.