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[caption id="attachment_5445" align="alignleft" width="500"] Late Iron Age/Roman woman showing large dental calculus deposit, from Cambridge area, UK. Photo: Alan Cooper[/caption]

Professor Alan Cooper and Dr Laura Weyrich appeared on the August 1 episode of the ABC's Catalyst talking about what ancient DNA and teeth can tell us sugar, bacteria, agriculture and disease.

"90% of the cells that you're walking around with right now aren't yours - they're actually bacteria. You're only about 10%. So, it's probably a better way of describing it as you being their human rather than them being your bacteria."

- Professor Cooper

"People have related these communities to anything from autism to obesity to depression. I mean, so, really, we have to think of these organisms as impacting everything from our mental health to our, you know, regular immune health.

"These communities change based on what we're putting in our body. And so a lot of the bacteria that we're finding in our bodies now are really associated with this high-sugar diet."

- Dr Weyrich