sentence2_structure: Woolly mammoths<>began<>because of hunting by humans
sentence1: 2) Mammoths became extinct on the Plains by 11,000 years ago, and although paleo-ecological conditions were worsening, the demise of mammoths may have been hastened by human predation.
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?