In surveying the diversity of living organisms, the 20th century evolutionary theorist Theodosius Dobzhansky did not see "a formless mass of randomly combining genes and traits." Instead he perceived pockets of discontinuity organized around available ecological niches - clusters of occupied "adaptive peaks" separated by rifts and valleys representing vacant spots in the natural world. Big cats, for example, formed their own mountain chain distinct from the cluster of dog species, and dog species were likewise separated from bears. By looking at the ecological and evolutionary topography of species, life's pattern would emerge.
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