The first known members of the genus Mammuthus are the African species M. subplanifrons from the Pliocene , and M. africanavus from the Pleistocene . The former is thought to be the ancestor of later forms. Mammoths entered Europe around 3 million years ago. The earliest European mammoth has been named M. rumanus ; it spread across Europe and China. Only its molars are known, which show that it had 8–10 enamel ridges. A population evolved 12–14 ridges, splitting off from and replacing the earlier type, becoming M. meridionalis about 2– million years ago. In turn, this species was replaced by the steppe mammoth ( M. trogontherii ) with 18–20 ridges, which evolved in eastern Asia around 1 million years ago.  The Columbian mammoth evolved from a population of M. trogontherii that had crossed the Bering Strait and entered North America about million years ago; it retained a similar number of molar ridges. Mammoths derived from M. trogontherii evolved molars with 26 ridges 400,000 years ago in Siberia and became the woolly mammoth. Woolly mammoths entered North America about 100,000 years ago. 
Human cloning would not be good idea because the reproductive cloning is not yet a fool-proof method. It took 272 attempts before Dolly the sheep was produced. This means 272 embryos either failed to develop properly or were discarded as defective. Also in other cases there were a large percentage of the animals born showed a high degree of abnormality and died quickly or had to be euthanized. And those that have successfully cloned have showed many health problems and none have lived to a ripe old age so far. And also there is no way of predicting what the intelligence level and capabilities of a human clone would be. What would be the psychological and societal implications for it as an individual? What kind of a life or future would it have? Since we don't know, many people consider it unethical to go ahead and clone.
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