A study of dog remains indicates that these were selectively bred to be either as sled dogs or as hunting dogs, which implies that a sled dog standard and a hunting dog standard existed at that time. The optimal maximum size for a sled dog is 20–25 kg based on thermo-regulation, and the ancient sled dogs were between 16 and 25 kg. The same standard has been found in the remains of sled dogs from this region 2,000 YBP and in the modern Siberian husky breed standard. Other dogs were more massive at 30 kg and appear to be dogs that had been crossed with wolves and used for polar bear hunting. At death, the heads of the dogs had been carefully separated from their bodies by humans, probably for ceremonial reasons.