General Thoughts

Life is temporary. No living individuals exist forever. All life forms must successfully reproduce their replacements or they become extinct.

Reproduction requires some form of movement. Some species expend a great deal of energy moving from place to place. This represents energy not being used for other life activities. Some species do not expend energy in this way. They hitch a ride on other species, or depend on wind or water currents to move them about. But, all species must have some means of meeting mates (in the broader sense) and in disseminating themselves throughout their environment.

One can easily observe such movement in larger forms such as birds, mammals, insects, and plants. Movement of smaller life forms is not as obvious to the human eye.

Consider a microorganism living in the intestine of a mammal. The microorganism’s needs are primarily met by their host. It has a comfortable home complete with food and protection. But, how does the microorganism spread from host to host? How does it reproduce it’s kind? Bacteria and viruses are smaller still. A common cold virus may do well in one host, but how does it spread to other suitable hosts?

One way in which microorganisms spread infections is to induce production of aerosols by its host. A cough or sneeze may spread a bacterium or virus from one host to any other suitable host when that host inhales the aerosol. Other ways include ingesting feces either directly or indirectly by eating food contaminated by feces.  Syphilis is spread by touch.

More indirect means of spreading infections include enlisting the aid of an organisms capable of movement. Examples include mosquito-borne malaria, tick-borne Lyme’s disease, Tsetse fly-borne sleeping sickness, snail-borne schistosomiasis, and dog, skunk, or bat-borne rabies.

Some animals become infected when they eat raw meat of infected plants or animals. Examples include sheep liver fluke (infected vegetation), human lung fluke (infected water chestnuts), trichinella (from rats or swine), fish tape-worms, beef tape-worms, etc. There might be a suggestion here to refrain from eating raw, under cooked, or incompletely cured meat (think Sushi).

There is even a suggestion that Toxoplasma organisms cause people to caress their cat, and thereby catch the disease from their pet.  Recently it has been learned that Toxoplasma in Rats causes them to be attracted to cat urine.  And thus the disease progresses.  A book called "Parasite Rex" by Carl Zimmer is an excellent read on the subject of parasitism.


This very general and abbreviated account of Natural History is written to encourage people to obtain more knowledge about life requirements. Too often our dietary habits, sociological behavior, and political inclinations are directed by ignorance.

How can one intelligently discuss the importance and ramifications of sociology and politics without more than a cursory understanding of the Natural History of Life?

I would be happy to receive and reply to any comments and suggestions you may care to send to me. I would be delighted to expand on any of the above topics at your request and/or steer you in the right direction for more information.

If you are interested in learning more, send an email to me, and I will be return an annotated bibliography of suggested readings to you. There will be no charge, and your email address will be protected from spammers, and will not be sold or given to any one. 

Fred Duerr, Ph.D.