August Weismann

"Heredity is not destiny, but it is the framework within which destiny operates."

"Nature's experiments are conducted on a scale of geological time."

"The body is temporary; the genetic information is eternal."

"Evolution proceeds without purpose, plan, or direction—only change."

"To understand yourself, you must understand the four billion years of struggle that made you."

"Natural selection is the only mechanism sufficient to explain life's complexity."

"The germ-plasm is the ultimate conservative force in nature."

"Life's history is written in the variations among organisms."

"Every creature is both a masterpiece and a temporary accident of nature."

"Evolution teaches that there is no design without a designer—time itself."

"Heredity is the invisible thread connecting all living things to their ancestors."

"The struggle for existence makes no moral judgments; it only sorts."

"Nature works slowly, indifferently, and with perfect efficiency."

"To understand the present, you must understand the evolutionary past."

"The germ-plasm is immortal, but each body is merely a temporary vehicle."

"Evolution is not kind, not cruel—it is simply the way of life itself."

"Variation provides the raw material; selection provides the direction."

"Every trait you possess has been tested by millions of years of competition."

"The doctrine of the continuity of the germ-plasm has revolutionized our understanding of inheritance itself."

"Natural selection acts not upon the individual but upon the variations that heredity presents."

"We must abandon the notion that acquired characteristics can be passed to offspring."

"The germ cells are sacred; they alone carry the promise of the future generation."

"Evolution is not progress toward perfection but adaptation to present circumstances."

"Heredity is the fundamental principle upon which all organic development rests."

"The struggle for existence is merciless, and only the fit survive to reproduce."

"Variation within species provides the raw material upon which selection works."

"The mechanism of inheritance lies not in the body but in the germinal substance."

"Each organism must be understood as a product of millions of years of selective pressure."

"The continuity of life depends upon the unbroken chain of germ-cell transmission."

"Adaptation demonstrates nature's infinite capacity for modification and improvement."