This blog is about the intersection between evolutionary biology and food. But also about practical applications, sustainable agriculture, and general tasty things.
How hard it is to read a scientific study? Should you bother to learn? I recently commented on a blog post on that subject.
Reading a study to figure out what to tell other people what to do is hard. Almost all the people who plant a pubmed reference in front of you to tell you to eat magic macronutrient XYZ or to avoid food X forever lest you perish from cancer are unqualified to pontificate on the subject. That includes many people with fancy titles. The people really qualified to talk about these things are not going to be pontificating. Nutrition science is too young for such surety.
But there is a much lower bar to be able to look up a reference and say whether or not it actually even possibly supports what the author who reference it was saying. That's fairly easy a lot of the time, since apparently many news outlets don't seem to care to fact check. I took a science journalism class in college and was taught a very meticulous and accurate way of writing that I don't see very often. A perfect and wonderfully topical example cropped up recently. The headline reads "Uh-Oh, Paleo: Cavemen Ate Less Meat Than Previously Thought." Surprisingly, the Fox News title, while stupid, is not completely inaccurate: "Secrets of the Caveman Diet." I get the feeling they are more interested in the SEO value of the paleo diet than ancient diets.
It took me more time than I would have liked to find the actual paper because they don't even link to the abstract. It turns out this paper is open-access, so anyone can read it, and that makes not linking to it even more suspicious. Well, I understand why. Just do a ctrl-f for "paleolithic." Don't bother with "caveman" because that's not even a technical or meaningful term. When I did that my computer made that annoying noise that I keep forgetting to disable that means it didn't find that word at all. Well, let's just try "paleo." Aha, something...but it's in the references...it's a paper in the journal " Biogeochemical approaches to paleodietary analysis." I could Google "paleodietary" and realize that the term encompasses all archeologically-studied diets from any time period, but without even reading anything, I've gained a lot of skepticism for the conclusions of news articles. The Fox News article is crafty and does say "first farmers" but makes a tenuous connection to the paleolithic.
I can then read the abstract and the discussion, the least science-y parts of the paper, which have several standouts anyone who is reading this blog post can probably pick up. Oh look at this sentence "This larger value goes some way to resolving the conundrum of interpretations of very high animal protein intake in isotopic studies of prehistoric farmers." Wait, so this whole thing was comparing to prehistoric farmers and not hunter-gatherers? Another minus point to the news articles. If you are a good reader, you can also figure out that the reason they did this study is that stable isotope analyses was based on animal data and they wanted some human data to compare that to.
If you want, you can delve further by reading a bit about that method. Considering how many of my readers are procrastinating computer coders with the next tab over open to their GitHub account or some API, I think a lot of them can handle this. The Fox News article, just like my science journalism teacher taught, describes this method.
To see how much meat ancient people ate, archeologists rely on the fact that protein is the only macronutrient that contains nitrogen. Different foods have different ratios of heavy and light nitrogen isotopes, or atoms of the same element with a different number of neutrons. So in a given ecosystem, scientists can reconstruct ancient diets by measuring the fraction of heavy-to-light nitrogen isotopes in fossilized bones.
But the body also preferentially stores heavier isotopes of nitrogen, so scientists calculate an offset to adjust for that tendency when determining what a person actually ate. Historically, the offset was derived from studies in which animals were fed diets with different protein amounts. [7 Perfect Survival Foods]
Using that offset, many studies estimate that between 60 and 80 percent of the prehistoric human diet came from proteins, with most of that from animal sources.
I'll just Google "isotopes diet." If you've taken a basic college level class in geology or archeology you probably know to Google "stable isotopes diet." The first results are a free and fairly readable paper and a blog post by a physical anthropology professor, John Hawks. Neither of these is easy to read, but if you can read .php or .ru files or are just a good reader, you can probably figure out the basics of the method. Fox News starts to get it right. But that last sentence is flat-out wrong. Isotope analysis is a way to determine trophic level of the protein in the diet, so where the protein might have come from in the local ecosystem. It is simply not capable of telling you what percentage of the total diet was protein.
There are more complexities to the method I could go into, such as potential inaccuracies of the method, but that's the overall gist of it. I'd note that I've also seen this method butchered in books popular with paleo dieters, claiming that because some skeletons from the paleolithic indicate they got most of their protein on the same trophic level as arctic foxes that their diet was like that of an arctic fox. That's the kind of thing this study is relevant to- whether or not we can extrapolate animal data to humans accurately in stable isotope analysis of diet. That's probably not as good for sexy headlines or SEO though, is it? The reality is that if we applied this we'd find paleolithic humans ate many different diets, with plant protein increasing with sedentism and with certain local ecologies. But in the wild plant proteins are not easy to come by. Most of them are not digestible by humans and many that are, such as certain wild legumes, are seasonal. And in the end, both of those articles fail to make the issue relevant in any comprehensible way, the blisstree taking nonsensical potshots at the paleo diet:
Many contemporary paleo diet gurus advocate a diet that’s 50 percent or more animal products (though contrary to what some people think, this doesn’t just mean chowing down on bacon and burgers — paleo dieters stress the importance of eating lean meat, fish and eggs that come from grass-fed livestock). This is based on the conventional wisdom that paleolithic humans ate a diet of between 60% and 80% protein, mostly from animal sources.
First, I don't know where I can get grass-fed fish but it sounds cool and if you know any sources, email me. Second of all, since when are animal products just protein? The ones I eat have plenty of fat. Maybe there is a parallel universe where I eat a 60% protein diet and have already wasted away from rabbit starvation, but in this universe I don't know anyone who eats an 80% protein paleo diet. Most people naturally gravitate away from absurd protein intakes because it's unappetizing and makes you feel bad, though lately I've found many people persist on diets that are exactly that for years and even decades. I don't like feeling bad or eating bad food, so I've never had that long-term problem.
We don't know what percentage of a paleolithic hunter-gatherer's diet was protein, we don't know that for "caveman" or for early farmers. It's just not knowable right now and probably never will be. We do know that for modern humans, there seems to be a physiology ceiling for protein intake which John Speth addresses quite readably in his excellent, though bizarrely expensive (worth getting on interlibrary loan) book, which requires humans not eat like an arctic fox, but be innovative and seek out either fat or carbohydrate in order to avoid potential costs of high protein intake. But that ceiling is controversial.
So there, those two news articles are essentially debunked and we didn't even have to discuss various nitrogen isotopes or anything really truly technical. In the end, we realize that the study in question doesn't tell us how those in the past really ate or what we should eat now. It's just a little piece of a large completely unsolvable puzzle. To even be able to realize that gives you immense power not to be deceived.
Hands down the best health book I read this year was The Definitive H.P. Lovecraft: 67 Tales of Horror in One Volume. Despite being about fictional creatures of terror from unholy abysses, I learned quite a bit from Lovecraft's depiction of the universe. The humans in Lovecraft's stories are baptized into the knowledge that the universe is older and more incomprehensible than they could have ever imagined. While the monstrosities and sublime ancient temples are quite terrifying, what is even more terrifying to the humans in the stories is their realization of how little they can ever really know. Those that get a taste of the mysteries often only do so at a very high price.
They called up some image from deep cells and tissues whose retentive functions are wholly primal and awesomely ancestral
I'm not sure I have any sort of particular cause in terms of diet anymore. It's gotten to the point where I'm just interested in the Paleolithic and not really very concerned with arguing about whether or not a potato is safe to eat or not.
Wouldn't it be nice if our nice little narratives worked out? The ones in which Homo sapiens sapiens is the protagonist and you can trace his illustrious evolution neatly through the ages. And he fits rather nicely in your romantic stories about hunters and mammoths so you can tell people that this is their heritage.
But in reality you don't get your nice story. Instead, you get ages and ages of dust and bones, in which every little shred of a skeleton is a prized, but dim, glimpse into ages long past.
In my anthropology class last year, one of the skull casts that caught my attention was the Kabwe skull, which is estimated to be between 125,000 and 300,000 years old. Not quite Homo Sapiens, the skull has some features of modern humans and some of Neanderthals. Homo rhodesiensis? Homo heidelbergensis? Homo sapiens rhodesiensis? Anthropologists could argue about it all day. Either way, this person died a miserable death. The first known incidence of dental infection in a hominid as far as I know, and the infection was bad enough to put some ugly holes in the bone and eventually kill the individual.
There is only so much you can tell from bones, which leaves lots of room for people to make stuff up. Stable isotope analysis seems quite promising, as they can potentially tell you the source of protein in the diet, but they can only tell that and nothing else, and the isotopes are subject to interpretation. For example, Lierre Keith in her error-ridden Vegetarian Myth claims that stable isotope analysis showed Australopithecus africanus ate meat, but in reality the data only said that the protein was from carbon-13 enriched foods, which could include grasses and sedges as well. Later investigations revealed that the carbon-13 probably was more likely from grasses and sedges, but the data is up for interpretation. Before you tear up your lawn to make dinner, it might be worth remembering that Australopithecus africanus is only thought to be a possible human ancestor and was quite a bit different from a modern human.
That said, stable isotope analysis puts to bed the idea that early Homo sapiens were getting their protein from the Paleolithic equivalent of tofu or the idea that Neanderthals definitely only ate meat (turns out that some ate fish too...maybe).
"Maybe", "later investigations revealed", "thought to be"- these are things that should give you pause whenever you encounter stable isotopes being used to argue about ancient diets. Have I confused you? Good, now you are less vulnerable to the abuse of bones in the name of various causes one way or another.
It can be used to estimate the trophic level and origin of the protein, but it cannot tell you whether the person ate a teeny tiny auroch steak and then 17 potatoes or whether they only ate mammoth. It cannot tell you the percentage of protein in the diet. It cannot tell you how much protein in grams. That information was lost when the person died.
Then there is the use (and mainly misuse) of animal bones and modern data from wild game species to argue various things about ancient diets. I read this latest paper, Man The Fat Hunter, with absolute glee because it uses many of the same questionable methods and comes to an opposite conclusion of many past papers, which overemphasize protein. The questionable method is taking bones of animals possibly consumed by ancient humans and plugging them into an equation with the modern wild game data and then saying this or that about the amount of fat or protein in an ancient diet. In this paper we have elephants featured, which is great, since elephants are very fatty, but unfortunately their presence or absence in bone assemblages is not a food diary. There is no way to know how often elephants were eaten, so there is no way to make an even sort-of accurate conclusion about %elephant and therefore %elephant fat in the diet. Whether or not the hominids in question were able to cook is also a point of contention.
One good thing about the paper is that it does try to address one issue, which is ceilings. In this case, the paper mentions possible ceilings for protein consumption and fiber consumption that could be used to build diet-estimating equations. Unfortunately, there are quite hard to determine, as they are affected by human genetic variation, culture, and environment. For example, there is possible a ceiling on the consumption of raw plant materials based on gut morphology (though if you have only skeletons you can only speculate on this) and toxins, but that ceiling can be raised with access to cooking and processing. To complicate matters further, their food sources may have been things you haven't even thought about eating. You can try to figure it out based on local paleobotany and starch microfossils, which can be hard to read. Once you've established that a microfossil on an ancient tooth is possibly Bromus secalinu, you might be able to figure out a little about how it was processed based on microfossil shape and local conditions and if you have a rich lab you might be able to collect it and do a full nutritional analysis, but you still have no idea how much of the diet it made up.
And what is the protein ceiling? It depends on the rest of the diet, an individual's health, and possibly genetics. Modern genetics adds some depths to the picture. For example, the fact that genetic adaptations for a starch-based diet seem to be part of fairly recent selective sweeps may give us a clue that Paleolithic human ancestors probably weren't eating mainly starch, but statistical genetics is in its infancy.
But genetic variation can add more confusion if we are talking about what to eat now. Many "paleo" dieters have learned the hard way that they carry alleles for hemochromatosis, which means they can over-accumulate iron, which has some pretty nasty effects. It would be interesting to know where this came from, as it clearly would be a liability if an ancient human ate meat-based diet, but ultimately whether or not Paleolithic hominids carried such alleles in high frequency is irrelevant to the millions of men (and some women) who are at risk. This represents a ceiling for them, though it can be modified through modern medical treatment.
Normal is of limited use if you are on the end of the bell curve- this is where personalized medicine and self-experimentation is important
So while it's not completely true we have no idea what Paleolithic hominids ate. We do have some good clues, but reconstructing the diet is pretty hard. That doesn't stop people from trying, but their results are on some pretty shaky ground.
My own method, which is about as accurate as some of these equations, is to observe the fact that a medallion of relatively lean wild boar goes absolutely perfectly with a seared hazelnut crust and dollop of mashed celeriac or potatoes cooked in broth. Maybe there is a reason that dishes containing a protein on a bed of delicious carbs AND fat (but not overpowered by them) is so appealing to so many? Who knows.
Erwan Le Corre, John Durant, and Andrew at the farm
So the Eating Paleo in NYC Meetup Group just did its first meatshare! We met bright and early in the morning to go to Glynwood Farm in Cold Spring, NY to pick up a lamb we ordered several months ago, as well as assorted other meaty goodies. Glynwood has been a farm since the 1700s, but these days its mission isn't just farming, since it is also a non-profit dedicated to improving Hudson Valley sustainable agriculture. Going there was a great opportunity to learn more about agriculture and the benefits of quality meat. Our tour was very diverse: WAPFers, paleos, raw meat eaters, and people just interested in grassfed agriculture!
Farmer Ken Kleinpeter gave us an overview of how livestock agriculture works. Most of the breeds he raises, like the White Park Cattle, are heritage breeds that do well in pasture. He explained that putting the average factory farmed cow out to pasture does not make for quality grass fed meat. He also told us about how government regulations make it difficult for him to bring meat to market. For example, it can be hard for them to book a date at the slaughterhouse they use, which is one of the few available that is certified humane. The really exciting thing to hear was that he is part of a regional task force that is developing mobile slaughter units for large livestock, which is huuuuuuuuuuuuge. It will make it much less stressful and expensive to process a large animal like a buffalo. Personally, I think slaughter regulations are ridiculous and it's too bad they have to jump through hoops for such nonsense as the regulation that the USDA inspector has to has their own office (they are going to have an office trailer). Furthermore, why is it OK to process chickens on-farm without an inspector but not cows? Are cows magically safe (haha) because of the USDA, but not chickens? Guess this is getting into rant territory, but you can read more on the unfortunate regulatory situation here.
The reason he can only sell frozen meat is that that it's expensive to keep meat fresh and distribution channels are slower. The animals are all very valuable on a small farm like Glynwood and the staff there takes great care during the slaughter process to provide as much comfort is possible. Ken also talked about how eating local grassfed animals raised on land that cannot grow anything else is the most sustainable way to eat, far more sustainable than a veggie diet utilizing grains grown in industrial monocultures or vegetables grown far away using lots of pesticides and petroleum fertilizers. The Vegetarian Myth by Lierre Keith is a good primer about this.
Ken said he feels comfortable eating his own meat raw and talked about how much higher the risk is eating meat raw from industrial sources because it is not just farm to fork...it is processed, shipped, handled by the grocery store... and meat from many different animals is mixed together, which means that it's hard to trace any problems that do arise. Pastured meat also is higher in healthy omega-3 fatty acids, fat-soluble vitamins, and other beneficial nutrients. Ken believes Americans should eat less meat and even though I'm part of this diet is is really kind of meat-centric, I agree. I personally feel better eating less meat, but meat that is higher quality: pastured and fatty gives me the energy I need without overloading me on protein, which makes me feel sluggish. I'm of the camp that thinks you should eat the amount of protein that your body actually needs, which really isn't much. Ken told us he often has trouble selling the really fatty cuts, but all of us eagerly snapped up fatback for making lard!
In terms of the actual lamb we got, I realized we next time I needed to plan more lbs per person, but I hope everyone enjoys their cuts. My own personal tip, having done a meat CSA before, is not to be afraid if your cut has a weird name. Last month I got pig cheeks and I wasn't really sure what to do with that, but a quick Google search revealed tons of delicious recipes! So I discovered an interesting and cheap cut AND
There are more meatshares in the future! If you are in NYC, vote for what animals you are interested in.