In a recent article on National Geographic News, scientists discuss the clues an early whale left behind. Two of these ancient whales, or archaeocetes, were found in the deserts of Pakistan nine years ago. One was a male. The other, a female, was pregnant. Of the many things these whales can tell us, one was that the calf was to be born head-first, indicating that the species was still dwelling on land at that time. Whales nowadays are born tail first, allowing them to swim right away. Therefore, this new species -- Maiacetus inuus -- must have come before whales that lived predominantly in the oceans.
Fossils are like time machines. Here are these remnants, these amazing leftovers, that can be seen today without having to have lived at that time. Fossils allow us to take a trip back to a former time, and imagine what it may have been like.