The anonymous science rebel

By Carlos Martinez Ruiz

Can you name 10 famous biologists? Even if you are a scientist, you will probably struggle to answer this question. If not, then probably just Darwin, and a handful of other names will come to mind. This is hardly surprising, Charles Darwin’s face is everywhere, especially in the UK, where his characteristic beard can be admired on every 10 pound note. And his notoriety is well deserved; not only did he offer an elegant and logical explanation for the striking diversity of life we see around us, he revolutionised our way of seeing the world, and our understanding of our own place in it.

That said, it is surprising how few biologists are famous, aside from Darwin. In other fields, such as physics or chemistry, the names of prominent men and women are well known; Marie Curie, Sir Isaac Newton, Albert Einstein and Stephen Hawking are household names. Is this because there are no prominent men and women in biology? Certainly not! But biology is a relatively young science, and we biologists are not very good at marketing.

Trying to list the contributions of all the remarkable biologists throughout history would be an overwhelming and tedious task, for both of us. So instead, I will introduce my own personal favourite: Lynn Margulis (Chicago, 1938), the science rebel.

Lynn Margulis in 2009

Lynn Margulis in 2009
Image used under a CC BY 1.0 from Wikimedia Commons

Lynn Margulis is the perfect example of unjustly obscure biologist: she was an excellent scientist, brave and smart enough to espouse ideas that were against some of the longest-standing assumptions in biology, held since the times of Darwin. The influence of Lynn Margulis’ ideas had the potential to cause a scientific (and social?) revolution, similar to that of Darwin, but this revolution is yet to come. Despite her important contributions, Lynn Margulis’ name is rarely uttered outside the halls of academia. Ironically enough, her first husband, the physicist Carl Sagan, is himself a famous and recognised figure among the general public.

Lynn Margulis’ work shook the very foundation of evolutionary biology, by explaining the earliest origins of complex, multicellular life on Earth, and showing that nature doesn’t always behave as selfishly as we have been taught.

To understand the fuss caused by Margulis’ ideas, we first need to set a little bit of context. Life on Earth comes in two main types: prokaryotic and eukaryotic. Prokaryotic organisms, such as bacteria, are simpler, and always unicellular.

Almost all life you can see with your own eyes (you, me, banana trees, mushrooms…) is formed by large aggregations of the more complex eukaryotic cells. The origin of these complex cells once puzzled biologists all over the world. Although they first appeared thousands of millions years after prokaryotic cells, they seemed to have done so spontaneously. But this just didn’t fit with Darwinian theory that evolutionary innovations appear gradually, over millions of years. How could this crucial evolutionary step have just popped out of nowhere?

And here comes Lynn Margulis, with an explanation as elegant and simple as it was controversial: eukaryotic cells are actually several prokaryotic cells working together. This might not sound ground-breaking, but the paper in which she described her theory was rejected 15 times before it was finally published in 19671. Even after publication, her ideas were intensively criticised and ridiculed by the scientific community at the time. Why? Because Margulis’ theory was against many assumptions of the Neo-Darwinian synthesis, the predominant paradigm in biology at the time.

First, her new theory implied that important evolutionary innovations could arise almost instantaneously. Second, it assumed that two unrelated lineages could merge to form a totally new one. And most importantly, it suggested that cooperation could play a major role in evolution. This was simply too much for many biologists at the time. Cooperation had no room in their selfish view of nature, “red in tooth and claw”.

Diagram showing the process by which several prokaryotes would fuse to form an eukaryote.

Diagram showing the process by which several prokaryotes would fuse to form an eukaryote.
Image copyright Nature Education 2010, used with permission.

But Margulis was right. The first empirical proof to her theory arrived in 19782 when an exhaustive analysis of different proteins showed empirically that mitochondria and chloroplasts, which are essential parts of eukaryotic animal and plant cells, originated as free-living prokaryotic cells. Since then, the evidence supporting a “collaborative” origin of eukaryotic cells has done nothing but increase to this day, and the most recent contribution was published as recently as 20153, four years after Lynn’s death. This study constructed a comprehensive tree of life for all eukaryotic organisms, showing once again that early eukaryotes were, in fact, “cooperatives” of multiple prokaryotic cells.

Nowadays Margulis’ theory is widely accepted, but rather than revolutionise the field of biology, it is still viewed as an exception in evolution. But its significance may reach much further than just a quirky example. Recently, evolutionary scientists (including Margulis herself) have started to wonder, “if such an important evolutionary step was driven by cooperation, isn’t it possible that other important steps in evolution were too?”

What would change if this were true? Well, maybe nothing. But Darwin’s view (and that of his less-acclaimed contemporary, Alfred Russel Wallace) of competition as the fuel of evolution has been repeatedly used to justify policies ranging from ethnic cleansing to the most savage expressions of capitalism. “We are just following the natural law”, they would say. What would happen if it turns out that the “natural law” is not driven by competition and selfishness, but rather by cooperation?


1. Sagan, L. (1967). On the origin of mitosing cells. Journal of theoretical biology,14(3), 225-IN6.
2. Schwartz, R. M., & Dayhoff, M. O. (1978). Origins of prokaryotes, eukaryotes, mitochondria, and chloroplasts. Science, 199(4327), 395-403.
3. Ku, C., Nelson-Sathi, S., Roettger, M., Sousa, F. L., Lockhart, P. J., Bryant, D., … & Martin, W. F. (2015). Endosymbiotic origin and differential loss of eukaryotic genes. Nature, 524(7566), 427-432.

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