Multicellular animals could not exist without the help of bacteria resident in whatever structure digests their food. Man has over 500 bacterial species living in his gut. Although a human body contains 10 trillion cells, the gut has ten times that many bacterial cells living in it. The relationship is truly symbiotic; our food gathering activities provide nourishment for the bacteria and the bacteria provide the digestive activity necessary to assimilate many nutrients. Our bodies make incredibly complicated adjustments to provide a safe home for these lifetime occupants. It is equally true that plants could not exist long without the activity of soil bacteria.

figure 10
Electron Micrograph of a Mitochondrion
Inside a Mammalian Cell

These cooperative arrangements are inherited from our earliest ancestors probably a billion years or more ago and are a product of biological evolution. I could elaborate endlessly on cooperation between species as a theme of evolution more universal than competition, but one more example. Most eukaryotic cells contain membrane bound structures called mitochondria. They are essential to energy production. Cells such as red blood cells that have lost their mitochondria in order to accomplish a specific mission, can no longer reproduce by fission and have a strictly limited life span.

Mitochondria contain their own DNA. It is passed on only through the egg; it has a different inheritance history than the DNA of the cellular nucleus. Mitochondrial DNA has been a useful tool in population genetics, but that is not my main point. We now think that mitochondria are descended from bacteria that were engulfed by nucleated cells around a billion years ago. They have settled down to a protected life inside the cell in return for providing the energy substances necessary to life processes. If this theory is correct, it represents the ultimate in cooperation between species arrived at during the course of evolution.

Universal biological cooperation is compatible with the loving God of Christian teaching. While the relationship between predators and their prey may seem to be one of struggle, predators fill an essential role in the ecology of wild life. For instance extirpation of the grey wolf in Yellowstone not only allowed an increase in coyotes to decimate mice and pocket gophers, but also permitted excess elk to destroy aspens and willows. Reintroduction of the wolf has righted these trends.

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