Humans Did Not Kill Off Megafauna
During the Middle-Late Pleistocene, one million to 10,000 years ago, more than 50 species of animal disappeared, the last to do so 46.4 thousand years from the present. The reason for the demise of the giant creatures is hotly debated. Some scientists claim that the spread of Man across the globe was the cause. This is suspect, however, because there were so few of them. Killing the odd animal would not have made a significant impact.
Many believe that the end date for megafauna is incorrect. As stated above, the theory that humans killed them off by definition means that people and animals lived side-by-side for a considerable time. Evidence in Australia certainly points to this - 13 species of large animals were here on human arrival. Moreover, the people mainly relied on subsistence strategies for food. Their weapons were not very efficient. A boomerang is highly inaccurate and the range of a spear is limited.
Megafauna died out over a long period of time, not all at a specific date. Species lingered on in many regions. Just assuming that humans killed them is a mistake and diverts from the discovery of why the large animals became extinct. This was a time of extremes in climate. Perhaps a series of wild swings in climate gradually reduced their number to the tipping point where reproduction did not take place.