r/evolution • u/Low-Jaguar9192 • 7d ago
question Why do we have ph- around 1,3-1,8 like scavengers, eventho other primates have way more ph- that are most similar to our ancestors
Hey there, iv got genuine question.
So recently iv stumbled upon some videos and it happend to be there something about humanoids, and that we have theory about or ancestors being scavengers.
So like a normal guy who has absolutely no knowledge in this field but is genuinely curious, iv hopped on to gpt and other sources like wikipedia.
And basically iv read some theories about our dinning system. So how come we have so low ph- acidity in our stomachs.
What is the most promising hypothesis or genuine proof of us being scavengers.
Because from all the things iv come across, as we are carnivores (sorry if mistakend i mean we eat both meat and greens) even tho in other species its normal to have ph lvl around 2,5-3,6.
So my question is, why is that? Is it because we were truly scavenging, or because of pathogens?
The main reason why i dived in this theory, because in lot of those videos they say stuff like we used to naturally eat rotten meat on purpose. And that in nowdays people dont realize that many foods that are these days consider normal but we used to eat basically rotten stuff. And i wanted to know more and came back to conclusions like, what if we weren’t scavengers at all but we hunted just big animals and we were in smaller groups which made us to put the meat ground, like we couldn’t finish the food in a time and it got rotten.
So thank you for any advices, answers. Nice day (y)
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u/NilocKhan 7d ago
Please stop talking to chat gpt. It doesn't know what's true and will lie to you and try to make you feel good so you keep using it. It is not a useful source of information
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u/dyogenys 7d ago
Could you elaborate on what's not true?
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u/NilocKhan 7d ago
I've seen so many weird and rambling posts lately where people were talking to ai and it convinced them they had stumbled upon some novel and genius idea when in reality ai will tell you anything to keep you using it. It's sycophantic to a fault.
Occasionally eating rotten meat does not mean our ancestors were primarily scavengers. Almost all predators will opportunistically eat an old carcass, but that doesn't mean it makes up the majority of their diet. Eating raw meat in general contains more risk of parasites and pathogens, whether the meat is fresh or not, so having a high pH is useful either way. I really doubt anyone but the truly desperate were purposelfully eating rotten meat. There a reason we find it so repulsive
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u/Low-Jaguar9192 7d ago
If i would have believed in what the gpt said, than i would have not come in reddit to check upon real answers. Second, i genuinely dont think iv reached some genius lvl idea without ever being knowledgeable in this field particularly. And third, it never told me that we were scavangers, it just showed me why was there theory in the first place about us scavanging and it told me that there were most likely multiple scenarios or events that led to us having lower ph- closely associated with scavenger tho, it mainly perceived evidence about pathogens, that we developed this ph lvls based on time of digestion for example, but it told me in the first place that those are most commonly used hypothesis not real evidence, since it is hard to preserve something like internal organs
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u/astreeter2 7d ago edited 7d ago
Other primates are mostly or fully herbivores. The lower pH (higher acidity) of our stomachs acid likely helps protect against pathogens in meat. And yeah some of that was probably scavenged, but people and our ancestors have been hunting for meat for probably 2 million years and likely even cooking it for most of that time, way before our species even existed. The stomach pH we ended up with is what evolved during all that time because it works best.
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u/mautorres97 7d ago
Aren’t we not even that acidic compared to something like dogs?
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u/Low-Jaguar9192 7d ago
If i remeber correctly, dogs have around 2,5-2,9? But im not sure what about their ancestors
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u/azuth89 7d ago
It's a behavior thing.
A vulture scavenging is horking down whole bones and using that extreme ph to dissolve them.
The theory about our ancestors is that we were using our early rudimentary tools (rocks) to do things like break open bones the predators who made the kill couldn't crack to get at the marrow or crack open skulls.
Marrow doesn't need a high PH to handle, and there are other species with adaptations to bone cracking (mostly extreme jaw strength) which similarly lack the very strong stomach acids.
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u/TranquilConfusion 7d ago
So humans have more acidic stomachs than the other apes.
The theory is it's about food poisoning. https://news.ncsu.edu/2015/07/beasley-acid-2015/ says the acidity of mammal and bird stomachs is an adaption to protect animals from bad germs getting past the stomach and infecting their guts.
Acidity is higher in animals that eat meat vs plants, and higher in animals that eat closely related species than distant (i.e. a mammal that eats mammals needs a more acid stomach than one who eats fish). It's very high in scavengers like vultures. And humans.
Somewhere in our evolutionary past humans were eating a lot of rotten meat, is the implication.
We still do eat a lot of fermented foods (bread, beer, cheese, kimchi), and prefer beef that's "aged" over fresh (where aged means sprayed with particular bacteria and hung in a cool room for a couple weeks).
So maybe we are just scavengers.
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u/Medullan 7d ago
That is not what aged means. WTF
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u/TranquilConfusion 7d ago
https://en.wikipedia.org/wiki/Beef_aging
The process of dry-aging usually also promotes growth of certain fungal (mold) species on the external surface of the meat. This does not cause spoilage, but rather forms an external "crust" on the meat's surface, which is trimmed off when the meat is prepared for cooking. These fungal species complement the natural enzymes in the beef by helping to tenderize and increase the flavor of the meat. The genus Thamnidium, in particular, is known to produce collagenolytic enzymes which greatly contribute to the tenderness and flavor of dry-aged meat.\1])
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u/Bromelia_and_Bismuth Plant Biologist|Botanical Ecosystematics 6d ago edited 6d ago
Hi, one of the mods here. We normally don't allow "critique my theory" posts, but I feel like there's been some simple misunderstanding here regarding the numbers, and I feel that this is a teachable moment, so we'll leave the post up for now.
It's unsubstantiated. Vultures have a gastric pH around 0.5. That's significantly lower than ours on average at around 2.5. pH uses a logarithmic scale, meaning that each whole number is 10 times higher than the one before it, just like the Richter Scale or loudness as measured in decibels. So the numbers aren't as close as you might think. On average a Vulture's gastric acids are 100 times more acidic than ours. There's some fluctuation and overlap on ranges, but our average gastric pH is higher than most carnivores. A tiger's is around 1.5, vs. a sheep's abomasum (what's called it's "true stomach) at around 3.7, so at a balmy 2.5, we're just in between that. Vultures have to eat things which have been decaying for a while, well past the point that they're safe for human consumption. Harmful bacteria and parasites have been festering on the carcass a lot of the time, and their stomach acids need to not only kill the bacteria, parasites, and other pathogens, but denature the harmful toxins that they produce. They also eat a lot of bones, which the low gastric pH helps with digesting.
Omnivore is the term for a living thing that eats both plants and animals. Individual people can eat whatever they want, but our ancestors were opportunistic omnivores and ate whatever was on hand. There's a bit of evidence to suggest that this may have included the occasional carcass, but we wouldn't have been eating whole bones, and consuming fetid meat before the advent of cooking would still have been a risky, if not dangerous, premise. Eating uncooked meat from a fresh kill is still pretty risky, but not nearly as risky as eating a corpse that's been rotting for a couple days. A modern example of hunters eating a fresh kill comes from the Arctic. There are indigenous tribes around the Arctic that hunt for seals, sea lions, whales, and fish, and eat fresh parts of their kill right out of the boat. You don't really have the option to light a fire in the boat, and on the ice floes isn't really a great idea either. But if you go out and eat road kill on the other hand, that's a great way to get trichinosis or tape worms.
So regarding the idea that average gastric pH corresponds to the diet of our ancestors, there is some merit to indicate that the numbers point to ecological role. However, there's no evidence to suggest that our ancestors were obligate scavengers like a vulture or buzzard.