No. 94: Jul-Aug 1994
Throughout much of Precambrian time until the onset of the Cambrian period some 540 million years ago, single-cell organisms dominated the planet. The goal of each individual cell was to prosper and proliferate. Competition with other cells, including those of the same species, was intense. Altruism did not exist. The most successful species were those that were tough and aggressive. Nevertheless, as the Cambrian began, some single cells suppressed their mutual antagonisms and formed partnerships. Thus were born the first metazoans -- the multicellular species. The road was now open to the evolution of what we term "higher" life forms. But before really complex organisms could evolve, the selfish, aggressive characteristics inherited from the ancestral single-cell species had to be tamed. Unfortunately, some of the controls that evolved -- and which we have inherited -- do not always work. Conversely, they sometimes work too well.
J.M. Saul has described how the appearance of cancer in complex multicellular organisms may be the consequence of the failure of biochemical controls evolved to curb cell aggression:
"Such failure may be seen as reversion to ancestral cellular behavior, or as failure of a cell with a monocellular heritage to perform metazoan tasks for which it was not originally designed. In such instances, the resultant types of wild and indiscriminate proliferation and variation would resemble pathologies classified as 'cancer.'"
Furthermore, Saul speculates, overcontrol could lead to autoimmune diseases:
"Within the individual metazoan, excessive antiproliferation measures would have occasionally resulted in focussed attacks against specialized classes of "innocent" cells, producing pathologies describable as 'autoimmune.'"
(Saul, John M.; "Cancer and Autoimmune Disease: A Cambrian Couple?" Geology, 22:5, 1994.)