80-million-year-old fossil ancestor of coffee and potatoes found near Sacramento

Image of fruit belonging to Palaeophytocrene chicoensis, an 80-million-year-old ancestor of the family that now includes coffee, potatoes, tomatoes and mint. The Sierra College Museum of Natural History is the permanent repository for this fossil.Brian Atkinson / University of Kansas

A fossil found near Sacramento is shedding new light on the origins of popular foods like tomatoes, potatoes, mint, and even coffee.

The 80-million-year-old piece of fruit pushes back the known origins of the ancestor to these foods all the way to the Cretaceous period, meaning these plants survived through the mass extinction that killed off the dinosaurs.

The fossil was originally discovered during the construction of a housing development in Granite Bay in the 1990s. It sat in a collection at the Sierra College Museum of Natural History in Rocklin until researchers from the University of Kansas examined it and realized they had something exciting. 

"What this tells us is that this really diverse group of plants … took part in this major ecological transition, which really kicked off the assembly of our modern ecosystems that we see on land today," said Brian Atkinson, a University of Kansas curator for the Biodiversity Institute.

Atkinson spoke with CapRadio anchor Randol White to explain why this is such a big deal. 

Can you describe that moment when you realized you had something special? 

I started pulling drawers just to get a first pass to see what they have. And this one fruit just kind of stood out. The head is a really distinctive sculpturing, patterning with all these pits and ridges on the fruit surface. 

It just kind of ignited all these memories of seeing these fruits of Icacinaceae, which are these plants that often form woody vines. And you see a ton of their fruits in younger rocks that are anywhere from 66 to 33 million years ago. They're everywhere. But you never find them older than 66 million years ago until now, or at least good evidence of them. 

It was kind of like an electric feeling, like I've been kind of looking for these things for a while, but could never find them. And here they are just looking at me right in the face, like, I'm here. So it was kind of like this really validating experience. 

How did you confirm your suspicions that this fossil was indeed an ancestor to such a huge group of foods we rely on today? 

What I did to confirm was I eventually asked to take the fossil out on loan and I spent hours in front of the microscope looking at the sculpturing patterns and how the pits are organized on the fruit, how the ridges are organized. And there are all these little micro bumps that are inside of fruit because part of it was broken open and there was just a list of features of the fruit that matched 100% with that family called Icacinaceae. 

How does this shake up what we understood before about this group of plants?

So I think we always suspected that this group of plants existed prior to the mass extinction event, but we didn't have any macro-fossil evidence. And by macro-fossil, I mean fossils that are bigger than pollen grains. So what this tells us is that this really diverse group of plants, the lamiids as well as Icacinaceae, took part in this major ecological transition, which really kicked off the assembly of our modern ecosystems that we see on land today. 

Does this find mean you or others will be looking for more examples of this fossilized plant in California? 

Now that we know that they're there, I think it's only a matter of time until more are described. So I think this is really exciting times for us. So I'm super looking forward to what is coming out of the West Coast and elsewhere in North America for Cretaceous in the next five years.