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Comment by taejavu | Hacker News Reader

From the article:

"Backing up this hypothesis is the fact that humans have relatively smaller large intestines than other primates. This indicates that our ancestors were eating food that was already partly broken down by fermentation."

IIRC another interpretation of the smaller large intestine is that early humans were eating more bioavailable food (i.e. meat) than other primates, which doesn't need to be broken down as much as more fibrous material (seeds, leaves, stalks etc). Can someone more knowledgable than me confirm or deny?

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Yes, meat being the driver is the more common (and simpler) explanation for our smaller intestines and larger brains. I guess plantbasednews.org just accidentally left this alternative explanation out.

That said, fermented foods could very well have played a part in it.

Plant based "news" is a misnomer unfortunately. They operate as an activist org rather than news. Nothing necessarily wrong with that but they can conveniently leave out facts that don't align with a plant based philosophy.

Did they fund the study? It sounds like they were simply promoting, writing about it?

Here are authors, they don't seem affiliated with the OP's "Plant based news" article.

Can't really fault an organization from promoting a study that aligns with them.

Authors and Affiliations Laboratoire de Psychologie Cognitive, Aix-Marseille Université, Marseille, France

Katherine L. Bryant

Hungry Heart Farm and Dietary Consulting, Conley, GA, USA

Christi Hansen

Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA

Erin E. Hecht

The article found at the URL submitted by OP ( https://plantbasednews.org/news/science/fermented-foods-huma... ) seems like classic blogspam, i.e. regurgitation, of this Harvard Gazette article:

https://news.harvard.edu/gazette/story/2024/02/did-fermented...

IMHO HN staff should, as the often do in such cases, update the OP link to point to the Harvard Gazette article.

As for the questioned passage, it appears to originate from the author of the Harvard Gazette article, reading there:

"This hypothesis is supported by the fact that the human large intestine is proportionally smaller than those of other primates, suggesting that we adapted to food that was already broken down by the chemical process of fermentation."

Thankfully, the perspective study itself appears open access:

.https://www.nature.com/articles/s42003-023-05517-3

And we can thus check it for addressing the meat consumption hypothesis, and indeed, we find:

"[…]

A smaller colon may reflect a reduction of dependence on fibrous plant material, given that a major function of the colon is to house bacteria that aid in the breakdown of enzyme-resistant carbohydrates to SCFAs. Did a shift to meat-eating, as suggested by Milton, permit this drastic reduction in colon size in the human lineage? Indeed, humans and members of the order Carnivora share a small colon size. However, the gut transit time in Carnivora is much faster than in humans. Although Milton postulates that this difference is due to our evolutionary history as plant eaters96, another explanation is that colon reduction follows from a reduced need to break down fibrous plant material within the digestive tract due increased bioavailability of nutrients before food is consumed—i.e., external fermentation (Fig. 1).

[…]"

As for the affiliations:

I can't find much on the obvious outlier among the author list, albeit I didn't check for very long, only an old interview here which appears partially misleading NOT due to content but due to what seem like incorrect social media references:

https://voyageatl.com/interview/meet-matthew-bagshaw-christi...

And an archive of their website:

https://web.archive.org/web/20190122012150/https://www.hungr...

The work breakdown given at the end of the paper in the contributions section looks like the following:

"K.L.B. and E.E.H. conceived the paper, K.L.B. and E.E.H. compiled data and analysis, K.L.B., E.E.H., and C.H. wrote the manuscript, with E.E.H. focusing on metabolic and nutrition components, E.E.H. on human evolution components, and K.L.B. on fermentation and culture components. All authors contributed to the final editing process."

Hope that clears things up for people arriving later to the comments section, and perhaps offers further avenues for exploration, albeit I'd advise caution as to avoid accidentally creating a tempest in a teapot

At least for me, I was responding to those that wanted to call the study biased, or invalidate, or question the results, because the original post was 'classic blogspam'.

The study was in Nature, not 'plantbasednews'.

Just because a blog with a bias, like 'plantbasednews', reports on a study, doesn't invalidate the study.

The 'blog' is just cherry picking the studies that align with their bias.

But lots of animals also eat (uncooked) meat. It doesnt explain why the developmental difference occured in humans but not other animals eating a similar diet.

But cooked meat, on the other hand, can explain this difference.

> But lots of animals also eat (uncooked) meat. It doesnt explain why the developmental difference occured in humans but not other animals eating a similar diet.

As to the gut: "The guts of carnivores are usually shorter and less complex than those of herbivores because meat is easier to digest than plant material."

https://en.wikibooks.org/wiki/Anatomy_and_Physiology_of_Anim...

As to the brain: These foods may give an animal the option to invest more into brain size, but that won't happen unless there is a local gradient in the evolutionary fitness landscape that gives a higher roi for larger brains in comparison to alternative investments, like more muscle mass, or just being content with the lower power consumption relative to intake, which makes the animal more resistant to starvation risks, etc.

Actually the big evolutionary advantage of humans is that they can thrive on a wide range different diets. Unlike other animals we can almost eat everything.

We are not the only omnivores, but I think it is an underappreciated trait of humans.

I believe that a lot is written about what is a healthy diet, but in reality, as long as there is no obvious excess or deficiency, and you don't have a specific disease, then any diet can be healthy. Vegan, carnivore, paleo, keto, kosher, whatever... even junk food. The human digestive system is very good at working with anything you throw at it.

The only thing is the less varied the diet, the more you need to care about potential deficiencies. Usually, there is a way, but unlike with a varied diet where you can rely on random sampling, you may need to be more explicit.

The psychological side is quite a bit more complex though. While a healthy diet is almost always possible from the point of view of our guts, we may not want to, because our natural incentives may not align with what modern society offers. What used to be rare is now abundant and easily accessible.

"healthy" in that "you won't die" -- not necessarily "healthy" as in "ideal for maintaining peak health". That's probably a bad comparison... But I'm not sure that you can count out the importance of the intestinal microbiome. It's not just vitamins or metals--one can be deficient in beneficial bacteria as well. These bacteria are why we can "throw anything" at our intestines. That's true until the good bacteria have nothing left to sustain them and die off.

> I believe that a lot is written about what is a healthy diet, but in reality, as long as there is no obvious excess or deficiency, and you don't have a specific disease, then any diet can be healthy.

Except the SAD standard american diet.

There's large parts of the food world that are completely inaccessible to humans.

Most plant material (i.e. "fiber", digestible by e.g. cows), carion, most raw meat (if we ate what dogs ate, we'd have constant stomach issues...)

>carion, most raw meat (if we ate what dogs ate, we'd have constant stomach issues...)

Humans have extremely acidic stomach acid (1.5 - 3.5 pH), close to that of vultures and dogs (1 - 2 pH).

Early humans and their predecessors, were very likely (at least partially) carrion feeders, and consumed raw meat for millions of years before they started cooking.

Fresh raw meat, yes. Not carrion.

Yes, early humans were likely carrion feeders among other dietary strategies. Archaeological and anthropological evidence suggests that before developing tools and techniques for hunting, early hominins would have scavenged carcasses left by predators. This behavior would have allowed them to access a high-quality source of nutrients like protein and fat, which are crucial for brain development.

The use of tools made from stones to break open bones for marrow and to possibly butcher animals suggests that early humans exploited carcasses that they found or scavenged from other predators' kills. Marrow and brain tissue, which could be accessed by breaking open bones and skulls, are highly nutritious and would have been valuable food sources for early humans.

Over time, as hominins developed more sophisticated tools and techniques, they likely became more efficient hunters, gradually shifting from scavenging to actively hunting for their food. However, the practice of scavenging would have played a critical role in the dietary habits of early human ancestors and contributed to their evolutionary success.

https://academic.oup.com/bioscience/article/64/5/394/2754213

Thank you.

Likely more accurate.

I'm not sure why anyone thinks any surviving development in an organism is due to this "one weird trick" thing, as opposed to a multitude of factors that rendered that organism fit for their environment, at least enough to pass said development on, anyway. Meat, fermented foods, fire, and a slew of other variables likely played a role.

Talking about evolution as though there was some single exploding popcorn kernel that caused change is a pretty narrow take on things. Sites like the one in the link only serve to perpetuate such shallow thinking on the matter, and in this case, likely to push a narrative.

> Talking about evolution as though there was some single exploding popcorn kernel that caused change is a pretty narrow take on things.

That’s kind of one of the predominant theories in evolution though: https://en.m.wikipedia.org/wiki/Punctuated_equilibrium

> Eldredge and Gould proposed that the degree of gradualism commonly attributed to Charles Darwin is virtually nonexistent in the fossil record, and that stasis dominates the history of most fossil species.

The theory deals with the morphology of animals in the fossil record but that’s the gist of it: the actual evolution happens really fast, usually to adapt to a large environmental change, and species enter a stable state where they very slowly change if at all.

> the actual evolution happens really fast

With the qualification, that they can be "fast" in geological time scales, which are rather big. It might look like rapid change in the fossil record, but that is a very compressed representation.

It's not just as simple as "probably just meat". Of course meat is important but i'd say in light of recent research fermentation and gut flora related concepts would be a better guess.

Cutting edge research into the Gut Biome shows its overlooked significance, connected to pre and probiotics and food, but also mental health, even going as far as questioning how much of "us" are really the gut biome.

People can heal various ailments even mental disease by getting transplants, it's a completely new and wild field of study, and holds much more weight than say eating or not eating meat.

I'm curious, but knowing how to safely ferment foods would seem indicate that one has an advanced brain. Are there any examples of other primates fermenting thier food (lacto, not alcohol - alcohol shrinks brains)?

Nature causes various food sources to ferment which is exploited by many animals.

> Nature causes various food sources to ferment which is exploited by many animals.

I did some searching and cannot find any evidence to support that.

Only the contrary, for instance: Some non-human animals are documented to consume fermented foods, but it appears to be somewhat infrequent, and limited to a narrow range of foods. from https://fermentology.pubpub.org/pub/2h9z1g3y

The article continues:

As a part of this unique relationship that humans have with fermented foods, it's perhaps not surprising to learn that humans have some adaptations associated with the consumption of fermented foods. Now, these technically aren't unique to humans. These are adaptations that are shared with African apes as well. In particular, there's two genes that we know about that signal this kind of special relationship with fermented foods among the great apes.

The first is the ADH4 gene. We have a special variant of this gene. It's an alcohol dehydrogenase gene. It basically lets us break down alcohol more effectively than many other primates. Alcohol is a byproduct of many types of fermentation. There are three major types of fermentation, two of which produce ethanol as a byproduct. Therefore, being able to break down ethanol provides us with an advantage in terms of being able to consume fermented foods.

The other gene is the HCAR3 gene. This gene codes for a receptor that's thought to make humans and great apes more sensitive to signals that come from certain types of microbes, particularly Lactobacillus. Lactobacillus are one of the key groups of microbes that are involved in food fermentations. Together, these two genes suggest that there's a kind of unique relationship between African apes and humans, and fermented foods.

Don't know why you were downvoted. We used to have a horse that would wait until the fallen apples were fermented, and then eat them to get drunk.

At least, that's the human explanation. It's more likely that she just preferred the taste of fermented apples and getting drunk was just a pleasant side effect.

Like what? Usually lacto fermenting requires a specific salt level. I know fruit tends to ferment, but that produces alcohol, which is a negative factor for brains.

Lacto only requires a specific salt level to keep the bad bacteria out. I doubt caveman humans cared much about sanitary conditions. Also, I doubt the vessels they used would be air tight (except to expel gases) like the ones I use.

Modern humans have genes to process alcohol and some populations don’t have the gene (Asian flushing). Alcohol and fermented fruit were probably sources of calories and drinkable water for many populations.

"Alcohol and fermented fruit were probably sources of calories and drinkable water for many populations."

I'm questioning how this could have preceeded the formation of advanced brains at a level to contribute to the formation of advanced brains.

There are tons of articles about monkeys routinely eating fermented fruits, so advanced brains aren't required for that.

E.g. https://news.berkeley.edu/2022/03/30/monkeys-routinely-eat-f...

I bet they did care a great deal about food poisoning. A few days of vomiting and fever could be a death sentence.

human pathogens can't live in alcohol. so a low alcohol liquid would be sterile and healthy for humans.

brain health isn't the big factor, it is outweighed by the not heaving out your guts by food poisoning.

"human pathogens can't live in alcohol. so a low alcohol liquid would be sterile and healthy for humans."

This isn't true at all. Beer can go bad and give you food poisoning.

Bad Taste, not kill you.

There are a ton of other studies exploring how beer/wine fermentation for alcohol also contributed to early human growth. Precisely because of this property.

> a negative factor for brains

try telling that to the parrots in the trees, they're a social animal and seem happy enough.

The study speculates that accidental fermentation by stashing food in the same location is how such foods were introduced into the human diet

It could be both: Fermented meat from scavenging. Sounds gross but actually many cultures still have fermented meat products in their cuisine

It’s not outside the realms of possibility that the invention of fermented meats (which includes salami and other similar sausages) arose when humans decided to eat the intestines of hunted beasts, possibly well after they ate the more desirable portions.

Cultures have different definitions of what is the desirable portions. In some native american tribes the most desired cut of the bison was the raw liver with the contents of the gallbladder squirted on top.

>Sounds gross but actually many cultures still have fermented meat products

Aged steak - a famous Western delicacy - is partially rotten meat.

Salami, chorizo, pepperoni.. are all fermented meats

There is an interesting series of scenes in the book Shogun where the main character gets some meat and wants to prepare it in the traditional manner by curing it. He hangs the meat outside but people are so disgusted by the stench that they steal it and dispose of it before he can eat it.

Natto... funazushi... surely the Japanese should have appreciated stanky food just as much as a European.

Yes. Could be both.

The problem is the simpler, 'meat' based answer, leads people to say "Brains grew big because eating meat, I think I'm going to pull up to the table and down a few pounds of ribs and wash it down with a nice brisket".

That's my excuse :-)

Were finding evidence of ... "milling for food dates back to the transitional period between Neanderthals and Homo sapiens."

From: https://nouvelles.umontreal.ca/en/article/2023/06/19/the-old...

I just don't buy that fermentation from random food piles is a driver for evolution...

Josef H. Reichholf, a German evolutionary biologist, writes that the first grain cultivations were not as nutritious and productive as they are today. His thesis is that grains were first used in fermentation – not for food, but alcohol consumption, along with other drug substances like poppy, betel nut, coca and others. Then, storage of these (luxury) goods reduced mobility of hunters and gatherers, which led them to settle down (still eating mostly a hunter and gatherer diet).

His book "Warum die Menschen sesshaft wurden" is summarized in https://oe1.orf.at/artikel/213690/Warum-die-Menschen-sesshaf...

For a scientific journal reference, see "The role of cult and feasting in the emergence of Neolithic communities. New evidence from Göbekli Tepe, south-eastern Turkey", Antiquity (2012), https://doi.org/10.1017/S0003598X00047840

> IIRC another interpretation of the smaller large intestine is that early humans were eating more bioavailable food (i.e. meat) than other primates, which doesn't need to be broken down as much as more fibrous material (seeds, leaves, stalks etc). Can someone more knowledgable than me confirm or deny?

Yep, it's also why the Giant Panda needs to eat so much bamboo in a day, they also have a carnivore-like short gastrointestinal tract.

The idea that humans were fermenting via persistent food caches a million years before we discovered fire, and doing it consistently enough to affect brain evolution is, well, a stretch.

Why is that a stretch? At a warm room temp fermentation is quite noticeable after 18 hours in a lot of raw edible plants. As little as 6-8 for some of them. You don't need a cache, simply carrying leftovers with you for the next morning would be enough. It's not a big stretch that a resource you would have to go alarmingly out of your way to avoid (by destroying edible food after gorging) would come before fire.

This is related to what I've heard called the carrier bag theory. Once you can acquire food, the next technological step is being able to bring it with you. A gourd, a large folded leaf is sufficient. Once you're doing that fermentation is inevitable.

> Why is that a stretch?

Because you need to do it over generations, so consistently that it effects the species evolution, selecting for a developing brain you can't support without the fermentation.

Similar developments, such as lactose tolerance, required a society that had already domesticated lactating animals.

Yeah I get that, it still doesn't seem like a big leap to me. Fermentation is just the early curve of the spoilage processes. All you need to exploit it is continued access to food you acquired recently.

Why?

Yeah not sure I understand the entire idea behind correctly.

To stick with other primates for now. Gorilla's have an obscene amount of muscles; adults need 8000 calories per day, compared to 2000-3000 calories for an adult human.

Somewhere, even though they eat low bioavailable food, even though they had to eat all day the heave muscle guys & girls had better chances of survival. Why do we think the brain's need are more special then a feature like muscles? Am I missing something here?

There is a decent amount of unfermented and uncooked food with lots of nutritional value a smarter brain can find, mainly meats (fatty parts especially) & nuts (if you are smart enough to open them), that would relatively on parr with the Gorilla way.

I'm sure as soon as tools, fire etc, became part of human culture it became even easier for those with more intelligence to became favorable. But that also needed to be in line with the development of more complicated social structures, either genetically or culturally.

Generally, the great apes are better adapted to plant diets, humans are better adapted for eating meat. Gorillas eat leaves and pith, and A LOT of it.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2964658/

Yes. But the parent commentor asked "why".

As in: why can a gorilla sustain it's immense needs to build muscles by eating a lot, but humans cannot do this to build a large brain?

To ask that question differently: why would humans need to change to meat/fermentation/cooking in order to grow brains, if they could "just" eat more, as other primates do?

Humans (since Erectus) _can't_ eat more. We don't have a big enough ingestion system for that. Our guts are tiny compared to other great apes. We're completely unable to survive on what chimpanzees eat, not to mention gorillas. The fire/cooked food hypothesis (and now this speculative one about fermented food) is that it made it possible to greatly reduce the guts, as well as chewing muscles. More calories and better nutrients (both cooking and fermentation greatly improves the nutritional value of many foods), and less need of energy for guts is what's supposed to be the driver here (and seafood has also been mentioned as a possible source of important amino acids which is necessary for brain development)

> Humans (since Erectus) _can't_ eat more

Again, the question is not if they can (they can't) but WHY. Or, differently, what is the cause, and what the effect.

The cause is selective pressure and the effect is evolutionary change.

but we can, you can perfectly fine live on raw meat (pork back fat) nuts etc. And Guts also shrank because they could. It sounds to me like this part mostly came after we learned to cook, then the body didn't need to waste energy on large complex guts. Hugely complicated brains such as Elephants & Whales do just fine on raw food diets.

Erectus are about 2 million years old, and they already had "our" body shape.. i.e. small guts. The question has always been - did they already know how to cook? It's somewhat early for fire control. But it is one of the arguments for the idea that fire/cooking came much earlier than we have physical evidence for. This study/idea about fermented food is exactly about this - if there wasn't fire that early, could it have been fermentation?

Some of it makes sense.

The question why & when humans gut could start to shrink. It seems more the other way around in my view, brain development helped develop cooking & other preparation methods and in turn to the need for less complicated guts.

Sounds like "standing up" was the real pivotal moment.

What do you mean? They eat mostly fruit and vegetables.

The top comment on this thread (https://www.quora.com/Could-a-human-being-survive-on-the-die...) matches what I've learned about this elsewhere. Just that "chewing for six hours a day" part is a problem..

As for gorillas - that's mostly leaves, shoots and stems. All very hard to digest, a human wouldn't get much nutrients out of that.

Sycamore figs are 100% edible, I think it's the predominant species grown in more southern areas.

That's fine, but you can't survive only on Sycamore figs - and that's the problem.

Spoken like you expect an answer when this is just incremental understanding. This is not a video game where we discover some tech tree humans followed and can then replicate that in say apes. Maybe Im reading too much into this? by seems like a-lot of screaming for why.

More probably the idea behind is some dill preserves company donated for the research.

Ah yes big pickle mucking with research...

Why not just read the actual study, to which the article links, and discuss that?

"One such proposed dietary change is increased meat eating, which has been argued to have been central to human evolution"

Behold the long comment train on a tangent unrelated to the study.

It seems that humans got Ruminococcus hominiciens (bacteria that is pivotal for brealing down celulosis) only after domesticating cows etc.

> Our evolutionary analysis strongly suggests that R[uminococcus] hominiciens likely originated in the ruminant gut and later transferred to humans, possibly during domestication.

> The human-associated strains possess functional adaptability highlighted by the acquisition of genes that can degrade specific plant fibers of monocots such as maize, rice, and wheat—major components of the human diet.

https://www.science.org/doi/10.1126/science.adj9223

It’s actually discussed in the paper.

> Explanatory power compared to other hypotheses

> The emergence of meat-eating, tuber-harvesting, and cooking have all been proposed to account for human brain expansion; why should our just-so story be given any additional credence? Below, we consider several explanatory advantages of the External Fermentation Hypothesis versus other current hypotheses.

https://www.nature.com/articles/s42003-023-05517-3

Cooked food, including meat, is hypothesized as the reason for a smaller digestive track. Of course, this needs fire.

Fermented meat would be a combination of both interpretations.. (sausages etc)

The paper addresses that, the tl;dr is that there is no evidence for hunting from this time period and that scavenging wouldn't have provided enough meat to make a substantial difference.

It's of course entirely possible that both fermented foods and a meat diet were pivotal, just at very different time periods and in different contexts.

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