When it comes to mammals, how big is too big?
Mammals vary enormously in size, from weighing less than a penny to measuring more than three school buses in length. Some groups of mammals have become very large, such as elephants and whales, while others have always been small, like primates. A new theory provides an explanation for why and how certain groups of organisms are able to evolve gigantic sizes, whereas others are not.<img src="http://feeds.feedburner.com/~r/sciencedaily/~4/G0c-WpDda_E" height="1" width="1"/>
