>>12512912If you're asking why these animals were so big, it's because hunting shrinks animals permanently in size and humans have hunted almost every large animal on this planet to extinction. The American Bison is a perfect example of this. It descends from the Ancient Bison which was much larger. The American Bison has only existed for about 8,000 years, far too recent for any kind of natural effect to have given rise to it. Not only that but smaller animals generally breed faster and so can tolerate hunting pressures better. Elephants are more intolerant of hunting then deer, for example. That's why there are still many deer species left on Earth but only two or possibly three elephants depending on how they're classified, when North America alone had five only 10,000 years ago.
