Margulis’ work centred around protozoa and unicellular algae that she called protists, or protoctista. As a protistologist, Margulis studied these eukaryotic species not as single entities, but mostly with respect to their symbiotic relationships. She studied them as interconnected beings, and not independent agents. Her remarkable near-intuition for the role of symbiosis in evolution led her to approach the field of microbiology from the viewpoint of ecology. Margulis opposed competition-oriented views of evolution, stressing the importance of symbiotic or cooperative relationships between species. She saw all the micro and macro organisms on earth working together for mutual benefit, in the same way we help our friends, and our friends help us.

In that regard, Margulis took a unique perspective, much different than the perspective of a regular microbiologist; she thought about the relationships among organisms and between them and their environment.

In line with her unique perspective, Margulis formulated a theory that proposed symbiotic relationships between organisms of different phyla or kingdoms as the driving force of evolution, and explained genetic variation as occurring mainly through transfer of nuclear information between bacterial cells or viruses and eukaryotic cells. Her organelle genesis ideas are now widely accepted, but the proposal that symbiotic relationships explain most genetic variation is still only a hypothesis, and remains highly contested.

Poster illustrating types of symbiosis

In fact, Margulis held negative views of certain interpretations of Neo-Darwinism that she felt were excessively focused on competition between organisms, as she believed that history will ultimately judge them as comprising “a minor twentieth-century religious sect within the sprawling religious persuasion of Anglo-Saxon Biology.” She wrote that proponents of the standard theory “wallow in their zoological, capitalistic, competitive, cost-benefit interpretation of Darwin – having mistaken him … Neo-Darwinism, which insists on [the slow accrual of mutations by gene-level natural selection], is in a complete funk.”

While this view seems extreme, her work in symbiotic relationships was outstanding as it was a way of seeing microorganisms that was hitherto ignored, much less considered as the driving force behind million of years of evolution.