Final answer:
In the past million years, only a handful of animals over 100 pounds have been domesticated, with success more prevalent among certain species such as cows and horses. Dogs, while common domestic animals, do not typically meet the weight criterion. Domestication and hunting practices by humans have played a role in past and ongoing mass extinctions.
Step-by-step explanation:
During the past million years, only a few animals over 100 pounds have been domesticated. Evidence from history and biology shows that domestication of animals occurred as human societies transitioned from hunting and gathering to more pastoral lifestyles. The domestication process often selected animals based on traits beneficial to humans such as docility, strength, the ability to survive on readily available foods, and rapid growth and reproduction.
The success rate for domesticating large animals, however, was not very high. This is partly due to the complex social structures, mating rituals, and dietary requirements of many large species that made them unsuitable for domestication. Among those few successfully domesticated large animals are cows, which have over 800 breeds recognized worldwide, and horses, domesticated in central Asia around six thousand years ago. Other domesticated animals include goats, sheep, pigs, and chickens, with the majority of them originating in Europe and Asia.
Although dogs are a prominent example of domesticated animals, with over 300 distinct breeds, they generally do not meet the criterion of weighing over 100 pounds, which is the focus of this question. While some individual dog breeds can exceed this weight, the domestication of larger animals is far less common. The domestication of animals such as llamas in Peru dates back to similar times as the domestication of horses.