Humans arrived in the Kaliko Islands about 7,000 years ago, and within 3,000 years most of the large mammal species that had lived in the forests of the Kaliko Islands had become extinct. Yet humans cannot have been a factor in the species' extinctions, b

The aforementioned argument above is well-presented and appears to be relatively sound at first glance. Since there is no specific evidence on the human impacts on the large mammal extinction, the author’s assertion that these extinctions were resulted from other factors seems logical. However, more light is shed on the issue and more detailed facts are concerned, the unsubstantiated assumptions lead me to question the validity of the argument.

First, the author assumes that lack of evidence on the relationship between human and the large mammal species proves that human did not influence the extinctions. With the absence of evidence that humans did not have any significant contact with mammals, the author hastily believes that extinctions were caused by other factors. However, he/she should take account of the fact that human can indirectly endangered mammals. For example, human could possibly consume plants or animals that were primary food resources for the larger mammals. In such a case, although humans did not directly contact with mammals, their actions could definitely yielded extinction of the larger mammal species. Therefore, more information is needed to verify the credibility of the assumption.

Another assumption the author makes is that lack of bones of larger mammals in numerous archeological sites proves that human did not hunt these species. Since archaeologists did not discover bones of the larger mammals at numerous sites where the bones of fish had been discarded, the author rashly concludes that lives of mammals were not threatened by human. However, in all likelihood, bones of mammals were not discovered by archeologists yet, and they might find sites with mammals’ bones in the near future. Even if bones might not be discovered, it is possible that the mammals’ bones could be easily decomposed compared to bones of fishes. In such a case, the author’s argument that human did not cause extinctions of mammals can be weakened.

Lastly, the author assumes the soundness of the conclusion that other factors such as climate change or environmental factors must have caused the species’ extinctions. However, the author should consider that these factors could also be influenced by the human actions. To be more specific, ever since human arrived in the Kaliko Island, they may cut a plethora of trees to build houses and light fires. Consequently, the deforestation occurred, and it might engender the climate and environmental change in the region. If this were the case, human’s action was the primary cause that led to extinction of the larger mammals. Therefore, more detailed information regarding the relationship between human’s arrival and environmental change should be provided.

The argument is not cogent on many grounds. To bolster the argument, the author should corroborate the aforementioned assumptions.