sentence2_structure: Woolly mammoths<>began<>because of hunting by humans
sentence1: at the dawn of human history, clumsy man-apes capered around the savannah in the hunt for berries, nuts, woolly mammoth and so on.
sentence2: Woolly mammoths began to go extinct thousands of years ago because of hunting by humans.
question: Why did woolly mammoths began to go extinct thousands of years ago?