Megafauna (latin for "large animals") like this mammoth used to roam around on the same ground that we walk on over 2 million years ago. I found this guy Baz (a canadian) who wrote a book about the megafauna that is available free online through creative commons. He argues that the megafauna might have been the first human-caused extinction to occur on earth (by over hunting). Others claim it was climate change, the Ice Age. In the end, it feels like a simple reminder that life on earth is anything but predictable. Especially when you take into consideration the larger span of time that Earth has been around, 4.5 billion years. Neanderthals date to 350-500 thousand years ago and homo sapiens have only been around for about 250-400 thousand.