Capable of swimming its entire life non-stop, one might wonder, how can a shark do this without rest? Sharks require water movement through their gills in order to breathe. This puts the animal in a precarious position because even if it could swim unconsciously, how could it know if it was heading towards danger? Sharks have the ability to rest half their brains while the other side remains active. Likewise, other marine animals such as whales, dolphins and porpoises have this same exact ability.

If there is a niche to be exploited, usually life will find a way to do it. Just as life originally sprung from the deep to take advantage of emerging opportunities on land, the same held true for animals that returned back to the sea. When food became scarce on riverbanks but appeared still plentiful in lakes, those that could exploit this new aquatic environment did.

Pakicetus, the earliest known ancestor of whales, was originally a land-based animal back in the early Eocene period. Like penguins and lizards today, this animal used its skills to swim and hold its breath underwater to exploit new food opportunities. Over the millennia, the fossil record shows the descendents of pakicetus (ambulocetus, rodhocetus and basilosaurus) gradually lost their limbs, grew flippers and became larger.

In the same family tree as whales, dolphins still show vestiges of these limbs in their flippers which contain finger-like bone structures. Occasionally, some dolphins are even born with an extra set of flippers that appear where their legs used to be.

The truth is there really is no perfect design in nature. All animals (including humans), continue to evolve. Even if our atmosphere became completely uninhabitable by every living organism's needs, the paleontological evidence clearly shows life is resilient and something will most likely evolve to survive the new environment. It may not be us, but it is unlikely all life will cease to exist until the sun reaches the end of its lifespan, becomes a red giant and scorches the last vestiges of life on the planet.

With the discovery of extremophiles that can survive in exceedingly inhospitable habitats, we now know that in at least one case, life can even flourish in arsenic. Likewise, the hot pools of water in Yellow Stone National Park and deep volcanic vents of the oceans have showed us that life can also survive in water heated to several hundred degrees. These strange developments may seem surreal but they are true. Where there is a niche that evolution presents, life will often exploit it no matter how bizarre or improbable it may seem.

View all Robert Haskell.'s articles

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About the Author:
Robert Haskell is a contributing author and manager of consumer affairs for Discount Office Supplies and www.worldatfocus.com.

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