Yeast like these are teaching us how simple evolution really is. Image courtesy of Masur, Wikimedia Commons

Evolving from something simple like a single celled beast into a slug, mushroom, cactus or a human seems impossibly hard. The series of precise DNA changes you need is mind-boggling to think about.

Unless, of course, the changes are easier than we imagine. For example, what if it is pretty easy to go from a single celled beast to a multi-cellular one? Or what if you can get increased complexity through easy to come by DNA changes? Then maybe it becomes easier to wrap your head around evolving complexity.

A couple of new studies in baker’s yeast are showing us just how easy it can be to build up complexity. Going from a single celled yeast into a multi-cellular one is pretty easy under the right conditions. And fairly common DNA changes can lead to increased complexity.

Taken together these two studies show us that increased complexity is easier to get than many people think. Certainly simpler than creating a 747 from a tornado in a junkyard!

I won’t have the space to deal with both studies in this blog. So I’ll talk about multicellularity in this one and then tackle the other, more complicated mutation example in my next entry.

How to Make a Multi-Cellular Yeast

In the first study, Ratcliff and coworkers used a very clever technique to end up with multi-cellular yeast. Basically they shook yeast in a big flask and only let those that were at the bottom reproduce.

After just two months, you had these beautiful beasts:

These aren’t just yeast cells stuck to each other either. That wouldn’t really be multi-cellular life.

No, as you can see in the video, these new creatures give birth to smaller multi-cellular instead of reverting back to single celled yeast. Being multicellular is now the default state of these yeast. This is true even when you stop the flask experiment and let them grow “naturally.”

Not only do they give rise to little versions of themselves, but they also have specialized cells within the snowflake cluster. For example, certain cells are willing to die so that the little juvenile snowflakes can separate from mom. No self-serving single cell would suicide like that unless it were part of a larger organism.

So the transition from one to many cells may be simpler than we thought. Which makes sense if current theories about life’s evolution are true. Scientists think multicellularity evolved dozens of times over the last few billion years.


Dr. Barry Starr

Dr. Barry Starr (@geneticsboy) is a Geneticist-in-Residence at The Tech Museum of Innovation in San Jose, CA and runs their Stanford at The Tech program. The program is part of an ongoing collaboration between the Stanford Department of Genetics and The Tech Museum of Innovation. Together these two partners created the Genetics: Technology with a Twist exhibition. You can also see additional posts by Barry at KQED Science, and read his previous contributions to QUEST, a project dedicated to exploring the Science of Sustainability.

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