Complete Evolution
Year of Discovery: 1967
What Is It? Evolution is driven by symbiotic mergers between cooperating
species.
Who Discovered It? Lynn Margulis
Why Is This One of the 100 Greatest?
Charles Darwin was the first to conceive that species evolved—changed—over time,
and the first to identify a driving force for that change—survival of the fittest. Darwin’s theories instantly became the bedrock of biological thinking and survived unchallenged for a
century.
Lynn Margulis was the first to discover and prove modification to Darwin’s theory of
evolution. In so doing, she filled in the one, nagging gap in Darwin’s theory. More than any
scientist since Darwin, she has forced a radical revision of evolutionary thinking. Like Copernicus, Galileo, Newton, and Darwin before her, Margulis has uprooted and changed
some of science’s most deeply held theorems and assumptions.
How Was It Discovered?
Born in 1938, Lynn Margulis was raised on the streets of Chicago. Called precocious
as a child, she entered the University of Chicago when only 14 years old. There she studied
genetics and evolution.
Since Darwin’s time the field of evolution has struggled with a problem called “variation.” Researchers assumed that variation in an individual’s DNA provided the “trial balloons” that natural selection kept or discarded. Those mutations that nature kept would
slowly spread through the entire species.
However, a nagging question could not be answered: What causes new variations in
the individuals of a species? Theories centered on random errors that somehow rewrote sections of the DNA genetic code.
Even early in her career, it seemed obvious to Margulis that this was not what really
happened. Margulis saw no hard evidence to support small, random mutations driving species evolution. Instead she found evidence for large, sudden jumps—as if evolution happened not as a slow, steady creep, but as sudden, dramatic adaptive advances. She saw that
evolutionary change was not nearly so random as others believed.
Margulis focused on the concept of symbiosis—two organisms (or species) living cooperatively together for their mutual benefit. She found many elementary examples of two
208