Evolution, Models of

Several major models have been used to represent organic evolution on earth. These models include the arc, line, spiral, circle, pyramid, and tree or bush or coral of life forms throughout biological history.

Aristotle (384–322 BCE), the father of biology, including morphology and taxonomy, taught that plants and animals represent a hierarchical line of eternally fixed forms. These kinds of life range from the simplest plant to the most complex animal, with our own species, as the only rational being, at the apex of this planetary ladder of the living world. Aristotle's great chain of being, from global minerals to celestial stars, was not an evolutionary interpretation of this universe.

Aristotle's worldview is grounded in the assumption that each type of life has a fixed essence. Consequently, this natural philosophy contributed to an antievolutionary view of organic history for nearly2,000 years.

Carolus Linnaeus (1707–1778), the father of modern taxonomy, classified the living world into groups of similar life forms (for example, the primate order includes our species, apes, monkeys, and prosimians). Linnaeus was not an evolutionist, although he did admit that a species may produce varieties of itself.

As the first serious evolutionist, Lamarck (1744–1829) interpreted organic history as an escalator of evolving species. He wrote that the human being has evolved from the chimpanzee in Africa and the orangutan in Asia. With little empirical evidence and no explanatory mechanism that could be tested, Lamarck was unable to convince other naturalists that species are mutable and evolve throughout vast periods of time.

[Page 895]Charles Darwin (1809–1882) wrote about the evolving tree of life in order to represent the branching out of successive species over eons of organic time. To also include the fact that plant and animal forms have become extinct throughout biological history, he preferred to interpret organic evolution as the coral of life. Darwin's empirical evidence, from paleontology to morphology, and explanatory mechanism of natural selection convinced several important naturalists that species either evolve or become extinct over time. His own sketch of evolving species illustrates the principle of divergence, thereby challenging all straight-line interpretations of organic history.

Ernst Haeckel (1834–1919) was the first evolutionist to draw a detailed picture of the tree of life. In fact, he drew several illustrations to demonstrate the historical relationships among groups of species as a branching tree of organic evolution. These illustrations may be seen in his home Villa Medusa, now a museum in Jena, Germany.

Several thinkers have interpreted evolving nature as a circle. Herbert Spencer (1820–1903) saw the universe in general and earth history in particular as a returning circle, each cycle representing the three basic stages of evolution, equilibrium, and devolution; yet each cycle would be different in its content.

However, Friedrich Nietzsche (1844–1900) held that given enough time, the identical cosmic cycle would return. In fact, for him, this same cycle would repeat itself forever. Nietzsche's awesome idea of the eternal recurrence of this same universe is the quintessential assumption of his metaphysical position.

Critical of Darwinian mechanistic materialism, Henri Bergson (1859–1941) argued that a vital force is necessary to account for the pervasive creativity throughout organic evolution. For him, this vital force has caused the creative divergence of plants, insects, and animals within biological history. In his interpretation of reality, our species now represents the apex of organic evolution in terms of consciousness. Yet, in the final analysis, Bergsonian philosophy gives preference to metaphysics and intuition rather than science and reason.

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