The low average life expectancy of former ages was largely due to much higher rates of infant mortality and violent or accidental death. If you survived infancy, and didn’t get killed by a rival tribesman or trampled by a mammoth you were hunting, you life expectancy would not have been much lower than a modern person’s.
Even if that were true (and it isn’t: nutritional deficiency, starvation, disease, and accident were major killers of adults, and even today hunter-gatherer societies have a median life expectancy below 60 years (pdf) even for those who reach age 15 – it’s 85 for the rest of us), the effect of longevity past reproductive age as an evolutionary selector is very weak, especially in societies that did not form large groups (where the elders could offer selection-enhancing protection or knowledge to the younger). And the Paleolithic lifestyle would have been protective against heart disease and cancer regardless of dietary effects because of it’s strenuous physical nature.
This discussion happens all the time, with vegetarians claiming that the meat-eating cavemen only lived to 30, followed by the carnivores pointing out that if you discount infant mortality effects agriculture actually lowered life expectancy, followed by claims like the above that if you discount almost all of the era’s forms of mortality, people live to modern ages. (Followed by me pointing out that if you don’t count people who die of anything, people live forever.)
Ultimately, these discussions are fruitless: not only have humans continued to evolve since Paleolithic times (lactose tolerance in Europeans may be less than 4000 years old, intelligence, language skills, decreasing skull thickness, and decreasing aggression appear to have genetically changed in the last 15000 or so – see Before the Dawn for an extended discussion), but until about 3000 years ago, life was so vastly different from modern settled civilization that trying to tease out the effect of one thing, like diet, isn’t feasible.
One small quibble right off, LDL are not “dense”, they are LOW Density.
An interesting take in an article linked to the op’s makes the point that replacement of saturated fat
Another take on the same and with newer data.
Bottom line seems to be that replacing saturated fat with polyunsaturated fat is good; replacing with carbs not good. Not enough data to be sure about whether monounsaturated would do as well or better in the same direct comparison but other data suggests it would do better. One can even hypothesize that the total amount is less important than the ratio but that would be very speculative.
(The newer study - March 23rd)
Since the discussion is, in effect, about what would happen ceteris paribus due to eating a certain sort of diet, I don’t think the factors you mention are relevant. I already mentioned violent death and accident. The fact that there are other factors that elevate mortality rates that are equally irrelevant to the issue of diet is itself irrelevant.
In any case, I was objecting to barbitu8’s facile claim that the average lifespan of “cavemen” was too short for them to be significantly subject to heart disease (or cancer). There might be something to that if in fact they rarely lived much past the sort of age usually quoted as their average at lifespan (i.e., around 30), since relatively few people today develop serious heart disease by that age. However, many people today have heart or circulatory disease by the time they reach 60. If, as you say, the median life expectancy for hunter-gatherer’s today who have reached 15 is around 60, then my point stands.
Very possibly. I made no claims about evolutionary effects.
I think you are responding to those discussions, not this one (certainly not to my tiny contribution to it). I will say, however, that if one is trying to ascertain the effects on life expectancy of a certain factor (in this case, dietary animal fat) it does make perfect sense to abstract away from other factors that may raise mortality rates. The crack about people living forever is obfuscatory.
The article states “Particularly refined carbohydrates.” That article does not disclose what “particularly” means in that context. Were any unrefined grains used in the study? Considering the well-known wholesome effects of whole grains, I seriously doubt that the study used any.
Before “quibbling” you may wish to read the post immediately before mine (and to which I was referring with the phrase “small, dense LDL”). That should make it clear that I was talking about the subset of LDL commonly described as “small, dense LDL”, and which is the subset of LDL most closely associated with risk of coronary disease. In fact, even the sentence of mine which you quote and “quibble” with, states essentially that, i.e. “Small, dense LDL is associated with coronary disease”. Moreover, it is immediately followed, in the very next sentence, with an explanation of why that should be so, i.e. “I’ve even heard it expressed that that may be so because of the enhanced ability of such small particles to enter (damaged) vessel walls, i.e. mechanically easier.”
Here is a concise summary of the notion of "small, dense LDL and its relation to coronary disease.
And, here is a random, but still informative abstract noting that “small, dense LDL” are the species of LDL most linked to coronary, and other, vascular disease.
But that is implicit in any claims that a certain diet is “better” because it is the conditions that we evolved under. And that was the context, wasn’t it?
A particular diet could, for example, help keep individuals stronger during their reproductive years and even long enough to get their children to a point of no longer relying on them for survival, and at the same time cause early death after that, and be a trait that would have been selected for during Paleolithic times.
A particular diet could result in traits that were beneficial for reproductive success in Paleolithic times but be, on balance, harmful in today’s world. Maybe more aggression in males, which gave more mating opportunities then, but causes more deaths in accidents now.
Doesn’t mean it was, or wasn’t.
It would only be when an individual being a wise elder brought a significant net advantage to his or her kinship, leading to more of his/her grandchildren living to reproduce, that a selection for longevity might occur.
Quibbling about how many lived long enough to have heart disease is silliness. Survival to reproductive age, opportunity to reproduce, and ability to have your children do the same, were based on other factors. And success then might depend on other traits than success now.*
In any case, anybody who tries to spin the op’s study to say that bacon double cheeseburgers are healthy eatin’ is misinterpreting the data. IMHO.
Karl sorry for not getting the context but also sorry that jargon gets so silly - “small dense low density lipoproteins”? Sheesh. Nevertheless, again, sorry for missing the context.
barbitu8, indeed all the study can claim is that replacing saturated fats with polyunsaturated fats reduces cardiac mortality and that replacing those saturated fats with carbs, in the manner done in these RCTs, does not. Their bias is obviously one that agrees that unrefined grains are established as good to have compared to refined carbs as evinced by this statement in the conclusion of the actual article.
*In that vein, this article from The Economist is interesting. Which males are determined to be “attractive” top females apparently changes based on the rate of disease in a society.
Tie it into other subjects under discussion at your own risk.