A strong-willed, independent thinker, Lynn Margulis is among the most celebrated names in twentieth century science. Her most prominent accomplishment is the evolutionary theory stating that symbiosis led to the development of the eukaryotic cell.

According to her theory, bacterial cells were ingested by other bacterial cells at some point in cellular evolution. They then developed a co-dependent relationship and eventually integrated as one cell. The results of this process are the mitochondrial and plastid organelles. This symbiosis engendered one of the largest evolutionary leaps: the formation of eukaryotic cells.

Margulis’ theories on evolution were, at best, accepted with a healthy amount of skepticism, if not outright rejected by her peers. The article first proclaiming these discoveries was famously rejected multiple times prior to its publication. Later, validated by genetic evidence, her symbiotic theory gained greater credence and became accepted into convention.

Her work symbolized the best qualities of science itself: that evidence can overcome the dogmatic beliefs people hold about their heroes. In this case, Darwin’s renowned theories were being retouched and moulded to better fit the observed evidence. Her work was contrasted to ‘neo-Darwinist’ theories where speciation — the divergence of species from their common ancestors — was thought to occur by accumulation of random mutations. With symbiosis, Margulis provided a clarifying glimpse toward an additional route of speciation that, together with mutational accumulation, more accurately reflects the evolution of life on Earth.

Margulis was a complex character and often considered controversial. The tenacity that had advanced her work despite little support early in her career may be partially responsible for this impression.

“I don’t consider my ideas controversial, I consider them right,” Margulis once said. These words symbolized her resolute mode of pursuing research, yet they also indicated the stubbornness with which her less successful works have come to be associated.

Despite the recognition and reverence that she was afforded, her ideas on the relationship of HIV to AIDS, on the import of nuclear transfer as evolutionary agent, and on the origin of the sperm were regularly thought of as inaccurate and misguided.

Also controversial was her association with the Gaia hypothesis. Developed in collaboration with Dr. James Lovelock, her goal was to establish a reciprocal relationship between organisms and the environment in maintaining life on earth. Though evidence for the hypothesis is disputed, it has become a cornerstone upon which many studies on the homeostatic cycle of organisms in their environment have been built.

The controversies and opposition she faced are perhaps symptoms of someone who dares to question the status quo. Margulis was willing to challenge prior beliefs and for this, along with her significant contributions to our understanding of life, she is a champion of science.

This article is published as part of a series of profiles in honour of the International Day of Women and Girls in Science on February 11.

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