One expert, Dr. A.J. Stuart of the Norfolk Museums Service in Norwich, England, argues that climatic change did indeed reduce some populations of Eurasian megafauna to vulnerable levels, and that hunting pressure supplied the coup de grace. One set of extinctions took place roughly coincident with the arrival of modern humans in Europe about 40,000 years ago, but others did not take place until later. While these later extinctions did not coincide with the first arrival of humans, they did coincide with the climatic disruptions that occurred at the end of the ice age. Another possible factor is that big carnivores shifted their attention to more kinds of animals as humans killed their preferred prey, thereby helping to press the substitutes to extinction. Once their prey became extinct for whatever reason, it is widely thought, many of the predator species vanished as well.
Some scientists see the idea of multiple causes as a kind of intellectual cop-out.
But the day when that happens, or when it becomes clear that several causes are responsible, appears far off. Edwards, W. E. 1967. The late Pleistocene extinction and diminution in size of many mammalian species. Elias, S. A. 1997. The Ice-age History of Southwestern National Parks.