We humans have evolved very differently from other primates. Is there one thing responsible for humans becoming human? Some evolutionary biologists think that the way we process our food, namely cooking it, could explain why our species developed so differently from others. Did cooking make us human? Dr. Richard Wrangham of Harvard University and Dr. Rachel Carmody of UCSF and Harvard discuss the impact that cooked food has had on human evolution.

This episode of Origin Stories was produced by Briana Breen and edited by Audrey Quinn. Music by Henry Nagle.

Thanks to Richard Wrangham and Rachel Carmody for sharing their work.


Richard Wrangham's Harvard University Website

Catching Fire: How Cooking Made Us Human

Smithsonian Magazine "Why Fire Made Us Human"

Rachel Carmody's Nature article: Diet rapidly and reproducibly alters the human gut microbiome


United States


00:00:03in this is the origin stories the leaky foundation pot I'm Meredith Johnson we modern humans have evolved in ways that are clearly different from the other living great apes we have these big complex brains small teeth and jaws and much smaller guts some of illusionary biologists think the
00:00:36key to these differences might be found in something that we all do every day reporter Brianna brain takes a look at the origins of cooking east I know it's almost time for you to eat this is Rachel Carmody and her son Theo fatal spend a lot of time
00:00:58thinking about food but not in the way you and I probably do Hey are you hungry I am currently a postdoctoral fellow at UCSF am in microbiology but I'm also a visiting fellow in the department of human evolutionary biology at Harvard home thank you making sense and is
00:01:21your home he this is my son Theo candy is twelve weeks old and he will be weaned on to cook food because of all the benefits that it provides in terms of softening the food in being easily digestible the right now you don't have any teeth at all
00:01:40so you're just getting breast milk thank he's fussy because he's can you tell me what you had for breakfast I had bacon and coffee and that's it with a newborn you don't get a lot of time to make a complex breakfast nutritionally it's probably not the best choice
00:01:59but it tastes so good Rachel looks at an interest and relates to human evolution the reason she's focused on this area is because of one person a my name is Richard running them I'm a professor of biological anthropology at Harvard University and I wrote a book called catching
00:02:15fire how cooking made us human Richard was Rachel's adviser at Harvard and they work together on a lot of projects they're interested in cooking because the change from a raw food diet to one that included cooked food probably impacted every part of our ancient relatives lives as soon
00:02:30as it was possible for our ancestors to be able to eat the food cooked on a regular basis what that meant was those individuals born with site is small teeth in small amounts and smaller gods would be the ones that use the food even more efficiently and as
00:02:46a result they would be the ones to survive better had more babies in other words the ones that were favored by the process of evolution and it turns out that humans are the only species that appreciate the difference researchers at Harvard found that champs when given a piece
00:03:02of food its raw well actually handed back to a researcher and wait to have it cooked and if you have ever seen a chimpanzee behave you know that waiting to eat is not something that comes easily for them so the fact that they will withhold consuming an item
00:03:20give it up actually and the chimpanzee will make this exchange willingly suggests that not only do they appreciate that the cooked item is better but they will ascribe value to it a deferred benefit all animals when given the choice show a clear preference for food that's been cooked
00:03:37cats dogs even in sex so if you are rearing caterpillars if for some reason you want to there isn't much productivity are your cockroaches as possible and that is a feed them cooked food down role food back to humans we have some very specific adaptations that according to
00:03:57Richard and Rachel seem to have come directly from this change in diet sell two million years ago body size gets larger brain size gets larger but interestingly we also have adaptations that suggest that we were able to choose less well if we think back to our closest living
00:04:16relatives and and look at chimpanzees chimpanzee spend enormous amount of time every day just chewing forget about even procuring the food there's a lot of time invested in that it just looking at the amount of time it takes them to break down the foods it's been estimated that
00:04:33they choose forty six hours per day humans today to food for less than one hour and looking back to those physical changes from two million years ago when our jaws teeth and GI system all got smaller we would have been able to eat as much raw food earlier
00:04:47species would have been way better equipped for a raw food diet in the nineteen nineties Richard was teaching at Harvard he was trying to figure out what could have caused the set of adaptations to happen all at once he realized he might have a piece to this puzzle
00:05:01in his own history I started thinking about how possible would it be for any human to live on raw food anyway in the wild and the reason I did so was because of a experience many years ago when for some days at a time while following chimpanzees throughout
00:05:21Gombe national park and studying the feeding behavior I tried to feed like a chimpanzee this was the early nineteen seventies Richard was a research student at Gombe national park in Tanzania with Jane Goodall this began when I simply forgot to pack some which is a was too late
00:05:38to %HESITATION organize my food supply for the day and I would simply survive all day on the gym foods I did go to one jangle at one point and say to her that I would like to really do an experiment of seeing how like a chimpanzee a human
00:05:55could live the life and survive and what I suggested was that four days is a time I would eat the chimpanzee diet and live like them so go naked in the forest I I'd like them and Jane said well okay you can do this accepts you got to
00:06:15wear a loincloth and I said well if you're gonna take the idea seriously than I'm giving up okay so hold on did you actually go out completely naked for a time period no I never did okay it was it was kind of a joke at the time but
00:06:32%HESITATION but if Jana said yes I would have felt obliged to tris got it but Richard didn't give up on trying a chimp diet he took it very seriously he ate everything they ate the leaves stems and fruits from trees as well as the occasional monkey racial comedy
00:06:49again I've known him long enough to know that he's willing to try anything in the name of science I believe he even tried to eat and it's the way that chimpanzees do by fishing them out of there and nest and of course he ended up with bites all
00:07:02over his face and it generally concluded that humans were not meant to eat a chimpanzee diet the experiment and go so well there is hardly any food that they eat you can fill your stomach with a you've got incredibly hungry %HESITATION it's simply impossible that was Richard just
00:07:18not used to this diet could other humans do better on a raw food diet still humans today can in theory survive on raw food but they don't thrive and we know this because a study was done in Germany of five hundred and seventy two raw food ist's and
00:07:34these are people who %HESITATION had followed a raw food diet for a period of at least three years and what these researchers found is that body mass index decreased with the amount of time someone had been a raw food S. but importantly what the researchers found was that
00:07:50fifty percent of women of reproductive age were not undergoing a very unsettling they were not reproductive if they were following a one hundred percent raw food diet so yes people can survive on a raw food diet but they cannot thrive in as a human evolutionary biologist when you
00:08:09are so energy limited as to %HESITATION impair reproduction that is not a sustainable strategy if fifty percent of early human females hadn't been able to reproduce we wouldn't be here today so who's the ancestor we need to thank for cooked food yeah I read the fossil record as
00:08:27saying that homo erectus was the first species that was adopted to cooking homo erectus lived about a million and a half years before the first modern humans it really needed cooked food and the reason for saying that is that they were the first species that had relatively small
00:08:42teeth and small guts and if not is right then the first species that sat around the fire and started learning to cook would be the predecessor SBC's called homo habilis that intermediate in my view would have been the one that started using file and then eventually got to
00:09:02the point where they discover that fire was so valuable for cooking food and they were able to cook the food so regularly that they became adapted to cook food but these ancestors probably didn't go straight from eating raw foods in their original forms to grilling over an open
00:09:19fire I think the first step in that transition might have been to use very simple tools of hammer stone for example or S. lacing tool but the big benefits are not going to come Intel ancestral hominins began to apply heat to the food when food is cooked you
00:09:37immediately get more energy more calories and there are two reasons for that one is that what cooking does is to increase the proportion all the nutrients that actually gets digested in the small intestine the second reason is that if you cook the food the food gets digested more
00:09:55quickly and it Dimond's less of the body to begin cooking someone had to be the first to experiment with putting food in a fire and eat that very first warm charge piece of food I think probably what occurred is that ancestral humans %HESITATION came upon foods that had
00:10:13been cooked naturally by bush fires or by volcanic activity or by lightning strikes and these ancestral humans as they walk through the Savannah and encountered something that had been cooked naturally might have it and enjoyed it and benefit from it they realize they could walk for that day
00:10:31were if they encountered these foods regularly they could produce more babies than they had in the past Richard and Rachel see other clues that our species probably had control of fire from very early on when we emerged as the first homo erectus then we could no longer climb
00:10:49nearly as well in trees as we had before and what that means is that when they almost certainly slept on the ground and having access to fire would have given them a way to keep safe from predators while they slept but archaeological proof of fire and especially proof
00:11:04human ancestors had control of fire has been hard to find we remain very puzzled by the fact that you will find archaeological sites even as recently as forty thousand years ago that have no trace of Florida and for which the archaeologists involved say look we've looked so carefully
00:11:25here that we think these people were living without five we've got pretty strong evidence of the control of fire going back one million years ago and this goes to %HESITATION vendor for cave in South Africa where we see deep in a cave evidence of controlled fires happening over
00:11:43a period of time that can't be explained by environmental disturbance because they are so deep in the cave we can't say for certain whether the burned bones that were found were burned for the purpose of cooking or perhaps they were burned as fuel bed in that cave our
00:12:00ancestors were able to use fire when and how they wanted and even without lots of evidence of engine fires there's still many other signs of the influence cooking had on us the process of developing into home was happy and clearly depended on having a big brain and so
00:12:15much of what we do is dependent on our intelligence something like a quarter of the food we eat goes to simply fuel our brain only possible if we have a rate of food supply that is made possible by a cooked food thanks to those early ancestors that learn
00:12:37to cook today we have larger brains and unlimited options for what and how we eat we've also added an infinite number of techniques for producing a preparing foods fundamentally the foods that we see in a supermarket today they're quite little resemblance to their their ancestors we've made fruits
00:12:54sweeter we've reduced their tannins and they're better quality is we've made them easier to peel we've made them brighter in color and this is change the nutritional value of these items and what we need in our diet today might also be involving more the BBC tried out its
00:13:16own experiment similar to Richard randoms champ diet nicely wellpoint lies the %HESITATION strange sounds like thanks for the call I'm going in the bed going in your in down that British volunteers lived in as the U. for twelve days and a what they called an evolutionary diet they
00:13:36stayed in tents next to disease primate area and eat a raw diet made of vegetables fruits nuts and honey this is for you today Johnny still struggling with the vegetables take have you ever read a piece of cauliflower never so this is the first time Colin and I
00:13:55much this man's here you can do it it just takes a lot it will be with when he started the program the participants were all over weight and on the verge of developing serious health problems at the end of their stay disease temporary residents emerged with a dramatic
00:14:18drop in cholesterol their blood pressure was lower and they all lost a significant amount of weight most of us probably don't want to try living in as you or experimenting with the champ died ourselves but today the modern highly processed diet is when that humans around the world
00:14:33aren't doing great on examining what our ancestors ate and why the eight it could help us make better choices for the future it's really only been in the last hundred years where we have the problem of excess calories this is not a problem that exists for most species
00:14:49and it's certainly not a problem that existed for us back in in human evolution I mean the problem then was always getting enough and so now when we think about human health and a raw food diet some people could reasonably expect health benefits because they're starting out in
00:15:08an obese diabetic state where it actually benefits them to extract fewer calories out of the diet if the important thing is to get as much energy as possible which is the way that animals in general are responding to the opportunity is then cooked food is always going to
00:15:27be best buds if for some reason you are short of vitamins then it is better to meet your food role because the process of cooking tends to reduce the concentration of vitamins buy somewhere from twenty five to seventy five percent sometimes and of course the other thing is
00:15:45that if you actually want to lose weight then it's better to eat your food role because you will get less energy back at Rachel's doesn't realize it yet but he's already benefiting from cooked food Finland having taken you're getting beacon indirectly because money can you see our the
00:16:09milk is contagious like in %HESITATION begin is good FOR origin stories I'm Brianna Breen %HESITATION yes on beacon thanks to Richard random Rachel Carmody and baby Theo we'll have links to more information about Richard rang him and Rachel comedies work in the show notes along with a link
00:16:36to Reagan's book how cooking made us human today's episode was produced by Brianna bring our editor is Audrey cleaned music and scoring by Henry Nickle origin stories is a project of the leaky foundation since nineteen sixty eight the leaky foundation has been funding human origins research and outreach
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