Origin of the domestic dog that was the most divergent group. The study found that the skulls of the "Goyet dog" and the "Altai dog" had some dog-like characteristics and proposed that the may have represented an aborted domestication episode. If so, there may have been originally more than one ancient domestication event for dogs as there was for domestic pigs. One theory is that domestication occurred during one of the five cold Heinrich events that occurred after the arrival of humans in West Europe 37 000, 29 000, 23 000, 16 500 and 12 000 YBP. The theory is that the extreme cold during
Endangered Species Act of 1973 was a substantial cause of Congress instituting the ban and many non-DDT oriented actions were taken on their behalf under the Endangered Species Act (i.e. captive breeding, habitat protection, and protection from disturbance). As of October 28, 2012, there are 2,052 total (foreign and domestic) species on the threatened and endangered lists. However, many species have become extinct while on the candidate list or otherwise under consideration for listing. Species which increased in population size since being placed on the endangered list include: Opponents of the Endangered Species Act argue that with over 2,000 endangered species listed, and only 28