Since the 1970s, there’s been this fad diet that keeps going in and out of fashion. And one can generally assume that fad diets are...well...fads. In five years, people lose interest again and it will have turned out that we should have been eating more vegetables and fewer chips and less sugar water, but we won’t do that because those things are delicious.   The Paleo diet is based on the idea that humans evolved eating a specific diet, and because we aren’t eating the food we evolved to eat, we aren’t healthy.    Leaving aside the fact that humans now are vastly more healthy than we were 50,000 years ago because of advances in complicated technologies like toothpaste and soap, there is a certain amount of logic to this, so it’s worth looking at. What diet did humans evolve eating, and would we be healthier if we matched it?   The trouble with the whole idea of matching what paleolithic humans ate is that if they were anything like today’s hunter-gatherer cultures -- and we think they were -- they ate very different things.    A 2000 study in the American Journal of Clinical Nutrition reviewed the diets of over 200 different hunter gatherer cultures and showed a huge range. Carbohydrates were between 22 and 40 percent, with roughly the same spread for fat, and protein was 19 to 56 percent of their diets!   The studies also found that these cultures have wide varieties of calorie sources. The Masai subsist mostly on meat, milk and blood, while cultures in New Guinea derive almost all of their nutrition from plants.   There are certainly massive differences between what we eat and what hunter gatherers eat, and we would be well-suited to include more dietary fiber, less salt, and WAAAAY less sugar and refined carbohydrates, but none of that is new information.    There was no one diet that fit all paleolithic peoples because their goal was to survive and they did it however they could, which they did marvelously and ingeniously.    All we can really say for sure about paleolithic people is that they did whatever they had to, to stay alive.   But even if we did pick one of those cultures and try to eat what they ate, we wouldn’t be able to because what they ate, aside from like deer and bison, isn’t really available to us. Almost all of the fruits and vegetables at the grocery store have been selectively bred for thousands of years to create the most nutritious and useful produce.   And the claim that our bodies haven’t kept up with the changes in our diets doesn’t really hold up, either.   The idea that humans can’t have evolved very much since the paleolithic era isn’t really true. Studies suggest that we’ve developed a few new adaptations just within the last few thousand years.   One of the more famous examples is that all adults used to be lactose intolerant, but thanks to a relatively recent mutation, about 30% of the world can now eat ice cream.   And according to research published in 2007 in the journal Nature Genetics, the ability to better digest starch also evolved over time.    The researchers tested 7 different populations, three with high starch diets and four with low starch diets.    They found that people from the high-starch populations were almost twice as likely to have extra copies of a gene, called AMY1, that codes for the starch-digesting protein in saliva. It didn’t matter whether they were European Americans or Hadza hunter-gatherers -- they still had more copies.   It’s unlikely that the extra copies of AMY1 came from one mutation that spread, because they were found in groups that wouldn’t have had much contact.    Instead, the researchers suggest that people with extra copies of the gene were naturally selected for in all the groups because they were able to get more nutrition out of their starch-rich diets.    Our bodies are versatile, and they’re equipped to handle a slice of bread or two.   Thanks for watching this episode of SciShow which was brought to you by our patrons on Patreon. All the people giving a buck or two or five a month make SciShow possible. Thank you all! If want to keep learning about our world and ourselves, head to YouTube.com/scishow and subscribe.