The cloning of humans is on most of the lists of things to worry about from Science, along with behavior control, genetic engineering, transplanted h… - Lewis Thomas

I can think of a few microorganisms, possibly the tubercle bacillus, the syphilis spirochete, the malarial parasite, and a few others, that have a selective advantage in their ability to infect human beings, but there is nothing to be gained, in an evolutionary sense, by the capacity to cause illness or death. Pathogenicity may be something of a disadvantage for most microbes, carrying lethal risks far more frightening to them than to us. The man who catches a meningococcus is in considerably less danger for his life, even without chemotherapy, than meningococci with the bad luck to catch a man.

Maybe there is a single spot, just one, where living organisms are holed up. Maybe so, but if so this would be the strangest thing of all, absolutely incomprehensible. For we are not familiar with this kind of living. We do not have solitary, isolated creatures. It is beyond our imagination to conceive of a single form of life that exists alone and independent, unattached to other forms.

Everything here is alive thanks to the living of everything else.