Another clue would be the fact that human beings get into ketosis very easily, whereas all other mammals become ketotic only in the late stages of starvation (or when fed completely unnatural diets by researchers).
Moreover, the fact that once we become keto-adapted, our skeletal muscles actively pass up glucose and ketones in favour of fatty acids would seem to be another indication of how well the human body does on a high-fat, low-carbohydrate diet…
I see some people arguing we shouldn’t be in ketosis all the time. Just listened to this:
The guest had been given a diagnosis of terminal cancer, and used a PKD (Paleo keto diet), along with other protocols, to overcome this. Even he no longer stayed in ketosis, and was eating carbs 2 days week. The host said he believes we as humans weren’t always ketotic, likely coming out each summer when there were berries and the like to eat.
I think it depended on where you lived and whether you followed the animals or stayed in one place.
@ctviggen Is it the case that cancer is, to a great extent, a more modern day disease? No doubt there were cancerous growths back in the Middle Ages, but infections (and war) likely killed far more people. As such, folks didn’t often age long enough to get to the point where they succumbed to a cancerous growth.
If this is so, then evolutionary diet trends and implications for forestalling cancer are not likely linked much at all.
Again, lasting long enough to reproduce is what would favor one particular diet over another in the evolutionary sense. Whether you lived a few years or a few decades beyond that (unless of course you were continuing to reproduce) would not likely have been a trait affecting species selection.
As such, diets that forestalled cancerous growths would not likely have played much of a role in our evolution.
Just guessing here. 
Those who think humans didn’t evolve almost if not exclusively in ketosis resulting from eating a diet of animal fat and meat have the onus of showing what they think our ancestors were eating that kept them out of it.
PS: I had the education of actually living for several years in an environment where ‘fattening up’ on carbohydrates during summer was not on the table. Even in an area favourable to wild berries it was not worth the time and effort to gather them.
The respected cancer researcher, Dr. Thomas Seyfried, is convinced, he says, that all cancers are the result of metabolic damage to cells. You’d have to consult medical statistics to be sure, but I certainly have the impression that there are a lot more cancers today than there were when I was a kid, back before the promulgation of the dietary guidelines.
The argument that there is more cancer because people are living longer these days is spurious. The average age at death is certainly greater these days, but that is the result of the availability of antibotics. Infant mortality is a small fraction of what it used to be, even as recently as a century ago. But people who survived childhood, and who weren’t felled by infectious disease in adulthood, usually lived to quite an advanced age, and I’d be willing to bet that cancer was still rare among those old people.
This may not be wrong, but it is certainly debatable. There is a hypothesis among evolutionary biologists called the “grandmother effect.” Basically it’s an argument that there is evolutionary utility for people to live well past reproductive age. I’m not qualified to have any kind of opinion on this hypothesis, but the fact that serious people are seriously proposing it does say something, I believe.
Again, it’s worth repeating that life expectancy is a tricky concept. Before they adopted the white man’s diet, the Plains Indians of the U.S. were noted for the number of centenarians among them, but because of childhood diseases, the average life expectancy was quite a bit lower than 100.
Indeed. As I was growing up, we would only whisper the word cancer.
We’re in agreement: Cancer was not likely a major cause of death in prehistoric times.
So the evolutionary benefit one might enjoy in terms of cancer-related survival through a paleo/keto diet would be weak at best.
Put differently: Since cancer was rare, there was little selection difference between those who never would have had cancerous growths (had they lived long enough) and those who would have experienced such growths (had they lived long enough).
Either way, few lived long enough to enjoy any paleo/keto dietary benefits as they pertain to surviving cancer. Ergo, not likely an evolutionary variable of note.
Yeah, I’ve heard about this but remain somewhat doubtful - especially given the short prehistoric lifespans throughout most (all?) of our evolution. Then again, with earlier puberty onset, perhaps that mitigates some of my skepticism.
I do firmly believe that today - i.e., in modern times - the “grandmother effect” (sexist of me?) is very real and strongly influences family outcomes. Having an older experienced woman in the household can make a world of positive difference on so many levels for all members of the family.
But I still find it hard to believe it was much of a factor in prehistoric evolutionary terms. Whatever the role of the grandmother may have been back when homo sapiens went about their daily business, I’ll assume she wasn’t nursing babies nor doing much strenuous cavework. Nor was she likely freeing up mom enough to make a difference in the tribe’s survival against the perilous odds of death. Perhaps the role that prehistoric grandmothers played was most evident in cave-dwellers’ divorce rates. 
OTOH, perhaps a “grandfather effect” afforded the benefit of a few scraggly old extra experienced warriors with spears joining the hunt? Or at least they barked orders at the rest - complaining that mammoths just ain’t what they used to be back in the day? 
I’m not arguing for or against how cancer comes about or whether we should or should not be in ketosis for long periods. I had just listened to that particular episode, and also other episodes where Brian Sanders was basically saying that the people adding fruit and honey to carnivore were doing good things.
Part of that is because he went to Africa and stayed with the Hazda, Masai, and more. The Hazda, he saw them eat honey and tubers. Even the Masai ate some tubers I think.
And I’ve heard other discussions with people looking at aboriginal-type tribes, and many ate higher caloric foods, as long as they learned how to detoxify them, or ate things with low toxins, like fruit if they were around.
Let’s all agree that plants for salads, things like broccoli or asparagus or cauliflower wouldn’t be eaten (let’s ignore that those are recent plants anyway). I’ve tried to grow leaf lettuce, and it’s a freaking ton of work to keep off the animals and insects, for almost no benefit. So, most things people eat are tubers or other high calorie foods like nuts or corn (assuming they are detoxified).
Dr. Danenberg has some ideas about cancer:
https://drdanenberg.com/unconventional-cancer-protocols/
I see here he increases carbs one day per week, not two. But he also fasts 72 hours multiple times per year. Seems to conflict somewhat.
Unfortunately, cancer is a brutal disease. If you look at later updates, his cancer has come back.
actually science does know this 
studies clearly show how ketones ‘change’ as are ‘used’ in the bodies of long term ketogenic functions. I have to go search for my most perfect darn science info to support this cause it tells all and wish I could find it on demand right now, but this is not some mystical function/process at all for long term ketogenic bodies. Ketones are used diff. from a newbie to a long term on how our bodies truly use them and what process we are in at our time in a ketogenic lifestyle so…but darn let me go try to find it
OK THIS IS not in response to above…this is just more good info.
Maybe I’m misreading and/or misinterpreting both the Ruled Me article and the above response from @PaulL here:
[quote=“PaulL, post:35, topic:76511, full:true”]
Ketones are not “synthesised,” they are a breakdown product, produced in the course of fatty-acid metabolism—just as charcoal is produced during the burning of wood. Technically, ketones are “intermediate metabolites;” just as charcoal is an intermediate combustion product. In both cases, the process can either be stopped and the intermediate product saved for later use, or else allowed to run to completion.
… To say that someone cannot produce ketones is to say that he or she cannot metabolise fatty acids, which is just like saying that a stove cannot burn wood. In either case, something is gravely wrong, and the end will not be good.
In the situation where fat fuel exceeds the capacity of the liver to oxidize it fully due to insufficient oxygen there are two options: (1) excrete the excess; or, (2) use whatever oxygen is available to oxidize only partially. Option #2 results in ketones.
Firstly, the liver is not the only organ using fatty acids as fuel. And if the liver is not getting enough oxygen, there is something very, very wrong. And oxygen is not the limiting factor for ketogenesis, it is, if I remember correctly, acetyl CoA. And lastly, the amount of oxygen required for ketogenesis is, necessarily, less than the amount needed for the full fatty-acid metabolic cycle.
Yes, indeedy. This comes as a surprise? Surely not.
The production of ketones in the absence of dietary glucose (also known as “carbohydrate”) is essential, because the brain needs to be fed, or the whole enterprise comes to a screeching halt. Fatty acids do not cross the blood-brain barrier, so it has to be ketones. And I don’t believe that gluconeogenesis is robust enough to meet all the brain’s needs, even if it were as efficient a process as fatty-acid metabolism.
What I mean is that there is a significant energy cost to deaminating an amino acid, then turning it into glucose or a fat, and then metabolising it. Better to just send out the little bit of glucose that is needed, and let ketogenesis work on the fatty acids. And to let the muscles work on fatty acids as well, since they prefer that even to ketones. For endurance needs, fatty acids are better than glucose, since they “burn” cleaner and produce a slightly larger amount of ATP. But fatty-acid metabolism is a slower process, which is why the muscles also use glucose for explosive power. More oxidative stress, but faster power when needed. Any fatty acids not needed for regular metabolism or for ketogenesis can be either wasted or stored. And as far as wasting is concerned, don’t forget that fatty-acid consumption by adipocytes can be uncoupled from the cells’ actual energy needs, and the excess energy wasted as heat.
And just as an aside, I may be missing something, but I don’t see any way that measuring the amount of circulating β-hydroxybutyrate could tell us much about ketone production or consumption, only about the gap between them. If all the TV sets the factory produces are being bought by vendors, you’re not going to catch too many of them in trucks on the highway, regardless of how many are or are not being made. You’d do better to look at respiratory quotient, or some other measure. Phinney and Volek talk about this in their studies of keto-adapted athletes.
I’m surprised no one mentioned Amber O’Hearn’s paper and talk on this subject, which make it clear that (quoting some of her tweets):
HUFA = Highly Unsaturated Fatty Acids. (at least 20 carbons, so linoleic isn’t one, but they include arachidonic, EPA, and DHA.)
The Inuit for that matter eat a lot of protein:
Inuit who consumed meat exclusively, were able to consume four kgs meat per day on a regular basis, most of it in a single meal, and ingestion of daily quantities of 15 kgs of meat per person has also been observed (Krogh and Krogh, 1914; Sinclair, 1953).
Miki-Ben Dor - The causal association between megafaunal extinction and Neandertal extinction in Western Europe – Application of the Obligatory Dietary Fat Bioenergetic Model, PhD thesis.
Link to the paper: https://escholarship.org/content/qt8wz5h9kp/qt8wz5h9kp.pdf?t=q3sb1q
Living in that extreme weather I can understand the need for more protein (for thermogenesis).