TCS Daily

What Ernst Mayr Teaches Us

By Sallie Baliunas - July 8, 2004 12:00 AM

Ernst Mayr, the Alexander Agassiz Professor of Zoology, Emeritus, at Harvard just turned 100 years old. He reaches this honorable age as one of the greatest evolutionary biologists of the 20th century. With his uncommonly lucid descriptive power, Mayr also writes graciously of modern biological sciences for the educated layperson.

Mayr clears away the mysticism protecting a speculation in biology, called Gaia, so that it can be cast as a testable, falsifiable scientific hypothesis.

The Gaia hypothesis, laid out in the mid-1960s primarily by scientist James Lovelock, tries to explain the observed, complex interaction between life and its environment in a global context.

An example is the considerable alteration of the composition of ancient earth's atmosphere by early life, which existed only in one-celled organisms. The early biota were ocean dwellers that thrived at least 3.5 - 3.8 billion years ago, and appeared, as best the scientific record can tell, after the period of intense bombardment ceased at the last stages of the formation of the solar system. With an atmosphere then of very little oxygen and high carbon dioxide content, many early biota derived energy from carbon dioxide. But these early organisms exhaled oxygen, and so successfully numerous were those colonies that they radically altered the composition of the air, by raising its oxygen content to near 20%, the approximate oxygen concentration of today's air.

As the oxygen concentration increased, oxygen's toxicity for early organisms caused many species extinctions. The extinctions -- plus radical remaking of the mix of gases in the air -- created the opportunity for energy-efficient, oxygen-consuming biota to evolve and succeed. This example of organisms greatly modifying an ecosystem seemingly to benefit the oxygen-consuming organisms -- from which richly diverse life later evolves -- is a case of the close connection of organisms and their environment.

Lovelock wrote in 1979 (Gaia: A New Look at Life on Earth) that all life on earth "can be regarded as constituting a single living entity capable of maintaining the Earth's atmosphere to suit its overall needs and endowed with faculties and power far beyond those of its constituent parts..." Incidentally, Lovelock never framed the concept of the earth as a living organism as an earth with purpose and perhaps intelligence, which both critics and proponents of mysticism have argued.

Mayr describes the Gaia hypothesis as a "control program" that oversees "the interactions, particularly chemical ones, between organisms and the inorganic world in which they live (including the atmosphere)..."

Mayr notes the "often steady-state balance of interaction between the activities of organisms and the response of the inanimate environment." That is, organisms make use of the environment in which they evolved, and there are feedback mechanisms whereby non-living parts of the environment react to the organisms, most often with chemical responses. Mayr elaborates, "This interaction sometimes results in such a balanced steady state that some authors have proposed" the Gaia hypothesis as a "well-balanced and programmed system" of the earth and life as a whole, as in the example of early organisms adding large amounts of oxygen to the air."

Mayr sums up, "There is, however, no well-substantiated evidence for the existence of such a 'program' and most evolutionists reject the Gaia hypothesis." Mayr concludes that the ostensible balance between organisms and the earth is "an opportunistic response of the living world to changes in the inanimate world and vice versa." As for the observed, strong feedback mechanisms, for example, when early biota added great amounts of oxygen to the air, the mechanistic response by the inanimate portions of the ecosystem may not be a branch of the instructions in an enormous master program, but rather the consequence of the laws of chemistry and physics. In other words, the master programming cannot be shown as successful or necessary in describing the close interaction between life and its environment.

The popular-culture belief in Gaia as a superorganism is superstition. There is every noble reason, however, to formulate and test Gaia as a scientific hypothesis. Many new ideas in science start as speculation, cultivated and refined as empirical facts are considered. Gaia may seem consistent with a broad range of empirical facts, and have great emotional appeal. But petitioning emotion and showing consistency with some facts fail to reach the class of hard science -- a good hypothesis, to be accepted, must formulate specific predictions that survive testing and be consistent with all known, relevant and well-observed facts.

Hypothesis testing is dangerous because it often leaves cherished cultural interpretations of reality in crushed shambles. Undermining popular superstitions is the result of deliberate action by humans to discover the facts of the material universe. Mayr's leaps toward facts have been the best heresy.

Good reading

Ernst Mayr What Evolution Is, 2001 Basic Books, 318pp


TCS Daily Archives