Can even a single-celled organism truly learn? In Episode 70, Jeremy Gunawardena with the Department of Systems Biology at Harvard Medical School talks with us about his replication of an experiment originally conducted over a century ago, which suggested that at least one single-cell organism – the trumpet-shaped Stentor roeseli – is able to carry out surprisingly complex decision-making behaviors. His article, A complex hierarchy of avoidance behaviors in a single-cell eukaryote,” [PDF] was co-authored with Joseph Dexter & Sudhakaran Prabakaran, and published on December 16, 2019 in the journal Current Biology.



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Hosts / Producers

Doug Leigh & Ryan Watkins

How to Cite

Leigh, D., Watkins, R., & Gunawardena, J.. (2020). Parsing Science – The minds of single-celled organisms. figshare.


What’s The Angle? by Shane Ivers


Jeremy Gunawardena: How on Earth from pure stochasticity does the organism or evolution find a way to get a probability that’s so close to a half?

Doug Leigh: This is Parsing Science: The unpublished stories behind world’s most compelling science as told by the researchers themselves. I’m Doug Leigh.

Ryan Watkins: And I’m Ryan Watkins. Today, in episode 70 of Parsing Science, we’re joined by Jeremy Gunawardena from the Department of Systems Biology at Harvard Medical School. He’ll discuss his research replicating an experiment originally conducted over a century ago, confirming that a single-cell organism – with no neurons – is capable of surprisingly complex decision-making behaviors … which may constitute “cognition.” Here’s Jeremy Gunawardena.

Gunawardena: I’m Jeremy Gunawardena. I’m an associate professor in the Department of Systems Biology at Harvard Medical School. I was born in Sri Lanka … Ceylon, as it was called at the time. I grew up in England. My father was in the Foreign Service. We got transferred to England and England became home. And in fact, I was a pure mathematician. At the time I was doing pure maths. If anybody had told me I would be working in a medical school and studying biology, I would have fallen off my chair laughing. One of my problems is a pure mathematician – I don’t know if it was a problem – but it made me a little bit different from some of my colleagues was that I loved pure mathematics. I loved it’s rigor and clarity and beauty. But I also wanted to have some impact in the world. That schizophrenia never left me and it took me sort of sideways because … I was a postdoc at University of Chicago and we’re just setting up a computer science program there and I got sort of sidetracked into teaching computer science. And that was just, you know, a hobby. It wasn’t work. Maths was work and computer science was play. But teaching computer science sort of opened my eyes to the idea that pure mathematics could be used to study very complicated complex systems. And that took me into industry for a while. And it took me a while to realize that computing systems: they’re great fun, they’re complicated, but they’re not really complex. And that realization sort of came about roughly about the time when the genome projects were starting. And I suddenly sort of wake up to this idea that complexity is really to be found in the living world and that biology is the source of it. And I didn’t actually think I was going to leave industry, but I had opportunity to come to Harvard as a visitor. And that was one of those experiences that completely change my own thinking. I realized that all the things I thought were interesting were actually wrong – or the wrong direction to take – and ultimately led to the position I have here, where I find myself, you know, sort of immersed in a biological world and trying to make sense of it with tools from mathematics.

Leigh: The single-celled organism that Jeremy and his team experimented with is called Stentor roeseli. As neither Ryan nor I had previously heard of them, we started out by asking Jeremy to tell us more about what they’re like, and what’s so striking about their behavior.

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