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 were extinct. Previous archaeological findings have suggested that early humans general

The argument indicates that the colossal mammals extinct within 3,000 years after the advent humans. According to the finding by the researchers, the author concludes that the human hunt the different giant mammals so excessively that they stopping exist in the earth. However, there could have been other explanations for the death of giant mammals, such as climate change, resource competition, and the changes in habitat.

First of all, the writer mentions that the huge mammals disappeared in 3,000 years after the coming of the human beings. Nevertheless, 3,000 years is a long time which is long enough to have climate changes. When climate changes, many species cannot adapt well and then disappear from the world. It is possible that the climate changed in Kaliko Islands and the new climate does not favor the gigantic mammals. In this way, sole the huge mammal species would disappear and other species left. Therefore, the climate factor could also lead to the extinction of huge mammals.

Secondly, the argument mentions that the researchers fund the bones of fish and simple tools for hunting. Probably, the humans might hunt the same targets as the huge mammals. Both human beings and gigantic mammals might take the same prey as their staple food. For instance, the enormous mammals also needed fish to maintain their lives, but was taken away by the people lived there. Thus, the competition of food resources between the human beings and enormous mammals might also cause the wiped out of the giant mammals.

Finally, the coming of humans could affect the environment of the Kaliko Island and then affect the habitat for huge mammals. In other words, the people there might change the huge mammals’ habitat. As a result, it would cause a harmful effect on the giant mammals. For example, the people in Kaliko might use their knives to cut down many trees and then might destroy the shelters for gigantic mammals. Hence, the gigantic mammals could not sustain their life so well as before when they lost their habitat and then died out as a repercussion.

To sum up, all the three alternatives could offer the valid explanation for the extinction of the enormous mammals in Kaliko after the human beings' arrival. Therefore, the conclusion in the argument, humans hunt giant mammals to death, would be challenge by the above introduced factors.