Humans who arrived on Kaliko islands 7000 years ago are being held responsible for the extinction of the mammals on the island. And the assumption for this arguement is that if the humans used to hunt fishes , then they are likely to hunt mammals as well. To deduce whether humans were truly responsible for the extiction or not we'll have to get rid of conclusions that are based on false assumptions .
It is mentioned that the human on Kaiko island used to hunt fish for a living on the basis of the fish bones that were found .And this evidence is being used to infer that since humans hunted fishes they are equally likely to hunt mammals as well.But such an inference is rather unfounded as there have no profound evidence that these humans hunted mammals. Similarly the assumption that the hunting of mammals is what led to their extinction is also unfounded , it could have been due to a variety of other reasons like lack of food , a catastrophe like a hurricane .
Also the stone tools that were found have been presumed to be the tools that were used to kill these mammals , while there has been no evidence of the same.If a tool would have been found embedded in the remains of a mammals , then one could then infer that mammals were indeed hunted using the weapons.But there has been no such evidence that has been found.
Thus from all the lack of evidence we cannot be sure as to whether humans were indeed responsible for the extinction of the mammals or was it due to other causes.