I wonder if anyone can point me to any figures or otherwise to  
support my argument.  I sit next to a guy at work who is sceptical  
about everything I say about food because he thinks a few thousand  
years, or even a few hundred years is a *really long time*.  He also  
thinks that evolution has speeded up since the industrial revolution 
(!) and I'm trying to explain to him the difference between cultural  
and biological evolution.

Is there any research on how long it has taken humans or other  
animals to adapt to a new environment?  I would really like to know  
how long it takes an animal's digestive system to evolve but I  
suppose that is guesswork based on teeth, bone structure and other  
related things, and not something you can see directly from fossils.

I'm hoping to prove to him that 150 years is NOT a long time, and  
certainly not long enough for humans to evolve from a diet of meat  
and veg to a diet of grains, beans and potatoes.

Thanks
Ashley