Mammoth Rocks Near Fort Ross, Sonoma Coast

There are rocks in the coastal moors just south of Fort Ross that are a) good for climbing and that are b) smoothed off in odd ways, high off the ground, that the California State Parks senior archaeologist has stated in writing was likely caused by mammoths rubbing their tusks. The sunset was spectacular that day too. (By the way, Fort Ross is pretty cool too.)

A Paleo *Cognitive* Regimen

This is cross-posted to Cognition and Evolution.

Paleo dieters avoid post-agricultural foods. The argument is that agriculture is a product of culture and so it introduced sources of nutrition that our genes haven't caught up with, especially grains, refined sugar, and other concentrated carbs. By eating vegetables and lean meats (so the argument goes) we are more in tune with paleolithic humans and therefore should be healthier.

There are any number of problems with that argument (not least of whic is that adherents often seem disinterested in empirical testing of it), but an interesting question is: couldn't we apply similar arguments to our cognition? The way we think about the world, or possibly even, that we think about the world, started undergoing profound changes about 40,000 years ago. Of note, this time corresponds with humans leaving Africa, developing specialized tools, hunting larger game that required team planning, and the spread of the current form of the FOXP2 gene and subsequent use of language and the cognitive modernization of humans; it marks the boundary between the upper and lower paleolithic. That is to say, until about 40,000 years ago, we solved problems in a primitive, isolated way, and knowledge could be shared only at a much more basic level. Suddenly we have language, reasoning, and mountains of cultural transmission in the form of tools and worldviews so that what we achieve in working memory can be expanded across a whole lifetime, or indeed indefinite lifetimes (i.e., among other things, the idea of an alphabet, hit upon by some clever Phoenician twenty-five centuries ago, allows us to more easily share these ideas right now). This has profoundly changed our physical environment in ways that have outrun our genes' ability to respond - including agriculture.

Therefore, shouldn't a person making the paleo argument for diet also make a similar argument for post-paleo (or at least post-lower paleo) cognition? That is to say, if you're really concerned that agriculture-based food is a threat to the fluorishing of H. sapiens because of its newness and alienness, aren't things like reasoning and systematic institutional research just as bad, if not profoundly more dangerous? Shouldn't we be approaching problems with blunt emotions and a vague memory of some chance association from last time we were in this part of the world with no way to obtain or share knowledge from others? Shouldn't the males of the species be getting in fights with people that look different from us or look at our woman for a second too long, with a resulting homicide rate of 30%? (The actual number for some hunter-gatherer groups.) This is what we're adapted for - our cognitive environment for thousands of centuries. How can the alien world we've built for ourselves in cognitive modernity not be hurting us?

In extension you could even make a Nagel-like argument here that paleo defeats itself, that if you think paleo is the way to go because profoundly biologically novel activities are threatening to an animal's well-being, then you should also eschew reasoning, and therefore eschew paleo, which was arrived at with a very un-paleo process (reasoning, communicating about it with large groups of people, and institutional research).

Cholesterol and Sunlight

If you do not like serious fitness-health geekiness, then won't you please look away now, madame or sir.

Humans make Vitamin D in our bodies when UV radiation (sunlight) strikes 7-dehydrocholesterol (7DHC) molecules in the skin. These same molecules are used as precursors in cholesterol synthesis. One day while running in sunny San Diego I thought about this and wondered what the relationship was between cholesterol and vitamin D. And of course the whole reason we care about cholesterol is because high cholesterol causes heart attacks. (It's rare in biomedicine to be able to make such an unequivocal statement as that, but it's very well-supported.) So how might this work?

Possibility 1: if you have a lot of cholesterol does this mean you have a lot of precursor available and therefore will also have a lot of vitamin D? And does this mean that by taking a statin, you'll lower your vitamin D production? My excuse for geeking out about this is my own high cholesterol. Half of your blogger's LDL receptors have a glutamine instead of an arginine at the 3500th amino acid residue. (Thanks Mom!) Hence without pharmacologic intervention, my LDL runs about 160. So did I save myself from premature coronary syndrome more by moving to California and getting lots of sun during my runs, than by taking that statin?

Possibility 2: Can a blockade of one or the other pathway result in diversion of more precursor to the other pathway?  By that argument, (a.) people congenitally unable to synthesize cholesterol would have loads of vitamin D from all the piled-up 7DHC, assuming they get enough sun and that the reaction does have some kind of ceiling.
OR (b) the opposite - do people who don't get much sunlight have loads of cholesterol from all the piled-up 7DHC not getting turned into vitamin D?

For Possibility 2a above, it turns out there are people missing the enzyme to make cholesterol (7DCHR); the disease is called Smith-Lemli-Opitz Syndrome (SLOS), and people born with it have significant deformities and health problems. Most interesting for our purposes is that although they DO have piles of 7DHC sitting around (because they can't make cholesterol out of it), they do NOT have more vitamin D or D precursors than other people. The research team even matched patients for season of collection (to make sure we didn't get all winter samples from SLOS patients, and sunny summer samples from healthy controls.) We don't yet understand how they can avoid poisoning themselves with vitamin D, but somehow they're compensating.

Which brings us to Possibility 2b. In 1996 a British group looked at the relationship between sunlight exposure and cardiovascular disease. These plots show what they found.  (Click on them if they're hard to see, especially the first one with the countries, which is kind of cool.)

Note that they included a cholesterol plot but a) this paper doesn't investigate the direct relationship between vitamin D and cholesterol and b) consequently they can't show vitamin D to be in the causal pathway, despite the interesting figures. The relationship with sunlight exposure they show is definitely interesting but we already know that physical activity, diet, and genetic differences all definitely play an enormous, hence confouding role. It's tough to compare Japanese with Swedes and say that sunlight is a causative factor in cardiovascular differences, rather than diet, which as you might recognize all differ substantially!

Furthermore, the SLOS patients are able to "rebalance their accounts" with respect to precursor utilization, so it's not unreasonable to expect that a similar mechanism could be operating the other way in health, erasing any benefits that cholesterol-precursor-eating sun may have. (For a different opinion, you can read That Paleo Guy's take on this, which is where I originally found this paper. I do not endorse most of his opinions, so if you want a hint on how to weight our conflicting arguments, consider that I'm the one in medical school. Just sayin.)

My conclusion is that this is interesting and I'll certainly be reading any articles that come out on this, but for now we just don't have evidence that sun exposure lowers cholesterol and therefore coronary syndrome risk. And if your output in thinking about sun exposure is all-cause mortality, then even with a putative cardiovascular benefit, we're going to be looking at a U-shaped curve because there are other considerations, chiefly among them skin cancer of course. So if you're concerned about your cholesterol, exercise regularly and take a statin if recommended by your physician.  In the meantime, I'll be running in the sun because it makes me happy.

The Paleo Theory Takes a Hit

[Added later: turns out caloric restriction doesn't extend life either, at least in primates; it's just unpleasant. And if you're reading this, you are one. Don't bother telling me about rodent studies.]

As nice as it is to see people trying to unify theory with action, it's even better to compare actual data against your theory, and when the theory doesn't fit the data, you fix the theory.  (Not the other way around.)  Or at the very least, you decrease your certainty about it.

Recently, Pontzer et al published a paper in PLoSONE (and Pontzer summarized it in the NYT here) about metabolic rates in a group in Africa.  Meet the Hadza:

The Hadza live in simple grass huts in the middle of a dry East African savanna. They have no guns, vehicles, crops or livestock. Each day the women comb miles of hilly terrain, foraging for tubers, berries and other wild plant foods, often while carrying infants, firewood and water. Men set out alone most days to collect honey or hunt for game using handmade bows and poison-tipped arrows, often covering 15 to 20 miles.

Paleos par excellence! A paleo wet dream! It doesn't get better than this without a time machine. So what did the researchers find, carefully measuring metabolism using two separate isotopes?

"...average daily energy expenditure of traditional Hadza foragers was no different than that of Westerners after controlling for body size." That is to say, "We found that despite all this physical activity, the number of calories that the Hadza burned per day was indistinguishable from that of typical adults in Europe and the United States. We ran a number of statistical tests, accounting for body mass, lean body mass, age, sex and fat mass, and still found no difference in daily energy expenditure between the Hadza and their Western counterparts."

There are two aspects to controlling one's physique: exercise and diet. The paleo evangelists of the world love to tell us endurance athletes that we're bad, bad people for doing long-term cardio instead of being miserable for short bursts in gyms. It turns out that side of the equation is less important than we all thought, judging by this research (which doesn't exist in isolation - look at the references). What it does mean is that diet becomes even more important.

Evolutionary Economics takes issue with the conclusion and also refers to Razib Khan's point that metabolism has undergone differential adaptation in humans who settled different parts of the world, and ate different things. (No kidding - for one extreme example, look at the fat distribution on the now very multi-ethnic sumo wrestler corps in Japan and this cannot be disputed.) That being the case, I would also argue that different populations of humans might respond differently to varying diets and exercise regimens. There has clearly been selection in muscle proteins, that your partly-sequenced blogger has found himself and his ancestors subjected to.

But most importantly, I hope the paleo exercise people start to settle down in the preaching.

The Chemistry of Runners High

Most interesting, there's an anandamide spike - to simplify, a pleasure chemical that is the endogenous compound for the receptor that THC stimulates. Chocolate has anandamide in it, which has been advanced as one reason for people's strange behavior around it. Include me on that list.

I originally found this at io9, which questions the evolutionary value of runner's high (or if it's just noise in an overtaxed system); one possible explanation is obvious in io9's link to a great Youtube video of an African persistence hunter. One of the reasons I started writing this blog was to puncture the Just-So stories of paleo enthusiasts who often claim that running is "unnatural" and bad for you. Yet here we have our species' remaining hunter-gatherers doing exactly that! (Apaches are reported to have done the same thing.)

Paleo Workouts: Running and Lifting Outside

"No no, let's move him this way. I've been neglecting my delts this week."

Move Naturally (MovNat) seems to be kind of a hybrid of middle-distance running and high-impact gym-type workouts. More importantly, it looks fun. I might try this. The idea that
is probably a useful vehicle for thinking about fitness, but it has holes, and people aren't consistent iin the way they think about it. Case in point, the subject of this very article talks about eating paleo but then gets inspired by the Tarahumara of Mexico. News flash: the Tarahumara are about as non-paleo-diet as you can get! They get HUGE portions of their calories from corn.

Still, this is the first time I've been intrigued by a trendy work-out philosophy. Because you can do it outside. And it's fun. And it would also seem to correct the deficiencies decried in lifting-oriented exercise (by endurance types) as well as in endurance exercise (by lifting types).

Previous entries on the paleo/lifting vs running debate:

- Paleo Running in Kenya and Mexico Highlands

- Paleolithic humans did eat grains - #1, #2, #3, #4

- The endurance vs. lifting jihad, in paleo terms: #1 and #2