We share this planet with a host of other organisms each with its own survival strategy. Every one of them has their own niche carved out and evolution gives them the tools to survive. As I sit at home playing host to the Streptococcus variant of life, this idea of sharing the planet with others sounds like total crap to me.
When North America and South America collided and formed the land bridge we call Central America species from both continents met and exchanged habitats for the first time. Sadly, nearly all of the species from delicate, wet South America could not survive the tough life in the north. North America, however, sent a fleet of big hungry animals to thrive down south. Pumas, bears, deer, raccoons. It was a field day. Only one animal from the south thrived in the new world, the armadillo. Who said life had to be beautiful? The harsh, unforgiving cimate of the north produced strong, robust and adaptable species. The delicate, unique South American continent gave us fragile and isolated creations.
Survival of the fittest is a fine motto that life on this planet has adhered to since the first dawn on Earth. This is why humans now face threats to our immune system. Most bacteria and virii have been reduced to shambles by increased hygiene, vaccination and modern medicine in the western world. Globally, mankind declared war on smallpox, one of our most dreaded enemies. We won. I think it's amazing to defeat another species. Go team! We are unintentionally squeezing out hundreds of other species every passing. Some of them are probably useful but I'd be willing to be bet we're crushing as many harmful ones as we are beneficial ones.
There seems to be only one front left to attack us and evolution dictates that we must be challenged on our weakness, the immune system. That which gives us our strength against invasion is being exploited by nature to ruin us. According to a grad student friend of mine, TB is teaming up with AIDS to give our medicine and immune systems a real run for our money. We're screwed, people. Someone just found out how to blow up the Death Star with a few photon torpedoes.
If you were worried about biological weapons being brought to bear in human conflict, get ready to watch the armada we'll need against Mother Nature.