A Mammoths were characterised by long and curved tusks and the northern species were covered by long hair.1These species belonged to the Elephantidae family which also included the two classes of the current elephant species and their antecedents. Similar to their close relatives, mammoths had a reputation for being huge. The largest of these species got to as high as four metres at the shoulder level and used to weigh up to eight tonnes. Male mammoths that were extraordinarily large would reach more than twelve tonnes. In most cases, however, mammoth species would only reach the size of current Asian elephants. At about six months of age, a small set of tusks first appeared and they were later replaced by a long-lasting set. The new set of tusks grew at approximately one to six inches per year. 2Studies conducted on the current elephant species indicated that mammoths most likely had twenty-two months of gestation before culminating in the birth of one calf. These mammoth species almost certainly had social structures resembling the current Asian and African elephants which are comprised of an all-female herd and a matriarch leader, while the males had solitary lives or formed lax groups after they reached maturity.
B It is hard to fathom in the current age of modernisation, urbanisation and automobiles, North America was once the home of mammoths, cow-size ground sloths, bear-size beavers, camels, and other strong beasts. About 11,000 years ago, these huge mammals, approximately 70 species in total, became extinct. The extinction of the species nearly corresponded with the arrival of the human species in the New World and dramatic climatic change factors that bore theories concerning perishing. Despite years of scientific research, the precise cause is still unknown. There are recent findings that support the contentious hypothesis that human beings were responsible for hunting that resulted in the extinction of the megafauna. The overkill model came about in the 1960s when Paul S. Martin brought the agenda at Arizona University. From that point, critics of the model have proposed that there is no evidence to sustain the argument that early Americans hunted the animals to the level of extinction. However, John Alroy, a paleoecologist at the University of California, argued in an annual meeting of the vertebrate paleontology that extinction as a result of hunting was believable and inevitable. By using computer simulation, he demonstrated that even an ordinary volume of hunting was enough to wipe out the animals.
C 8Assuming there were 100 human beings at the beginning with a population growth of 2% per year, Alroy found that a group of 50 human beings was able to kill 15 to 20 mammals each year, so human beings could wipe out the entire animal populations within 1,000 years. In particular, 14large mammals are susceptible to pressure because their gestation period is longer as compared to the smaller mammals and their offspring need protracted care.
D 3The assessment by Alroy does not have universal consensus though. To start with, the outcome is subject, in part, to the estimated population size of extinct animals and the estimates are not reliable. 4Ross MacPhee, a mammologist from New York City's Natural History Museum, presents a deeply pointed criticism of Alroy's findings by calling attention to pertinent archaeological records that only contain a handful of stone tools embedded in the bones of mammoths and none of them are recognised as coming from other megafaunal corpses. 11This is contrary to the expectation that hunting drove these mammals to their extinction. Certain animal species had vast ranges and an example is the humongous ground sloth that lived in the far north region up to Yukon and far south down to Mexico. The range itself would make it improbable to slaughter the animals to the extent of causing extinction.
E MacPhee agrees that human beings were most likely responsible for the extinction of the mammoths and other species that existed at the same time, but not in a direct way. 13His suggestion is that people likely initiated very lethal diseases, probably through parasites or the dogs, occasioning a widespread epidemic among species with poor immunity in the new biosphere. Similar to Paul Martin's overkill model, large mammal populations would find it hard to recover. The recurrent lethal disease outbreaks would quickly lead to extinction. 5MacPhee does not present any empirical evidence to support his hypothesis. Also, it can be difficult to find the evidence since lethal disease would have killed these animals far too quickly to leave signature on the bones. However, 9MacPhee is confident that DNA and tissue analyses from the last species of mammoths would reveal the deadly microbes.
F Another proposition on what caused the extinction of North American mammoths has nothing to do with human beings. Supporters of the new proposition blame the weather for the loss. 6-10Pleistocene epoch era was characterised by significant climatic instability as Russell Graham, a paleontologist, explains.The harsh weather caused the disappearance of some habitats and some of the species that had formed communities were driven apart. Some animals seized the opportunities and flourished.7However, the intensifying harsh environment may have been too much for megafauna and caused their geographic range to diminish. This spelled doom for the huge animals which needed larger spaces to survive. As Graham stated, although sizeable populations survived the Pleistocene, the Younger Dryas occurrence was too much for them. Alroy is certain that the demise of the titans can be traced to human hunters in the period of extreme cold, the Ice Age. 12However, Graham believes that changing climate scenarios could predict with accuracy that these species would still become extinct eventually.
