Bio-thermodynamics and aging

I suspect nature is constrained by basic physics/chemistry/thermodynamics in a variety of interesting ways.

For example, chemical reactions (and thus biological processes) proceed more quickly when they are warm than cold–this is pretty much a tautology, since temperature=movement–and thus it seems reasonable to expect certain biological processes to proceed more slowly in colder places/seasons than in warmer ones.

The Greenland Shark, which lives in very cold waters, lives to be about 300-500 years old. It’s no coincidence:

Temperature is a basic and essential property of any physical system, including living systems. Even modest variations in temperature can have profound effects on organisms, and it has long been thought that as metabolism increases at higher temperatures so should rates of ageing. Here, we review the literature on how temperature affects longevity, ageing and life history traits. From poikilotherms to homeotherms, there is a clear trend for lower temperature being associated with longer lifespans both in wild populations and in laboratory conditions. Many life-extending manipulations in rodents, such as caloric restriction, also decrease core body temperature.

This implies, in turn, that people (or animals) who overeat will tend to die younger, not necessarily due to any particular effects of having extra lumps of fat around, but because they burn hotter and thus faster.

Weighing more may trigger certain physiological changes–like menarchy–to begin earlier due to the beneficial presence of fat–you don’t want to menstruate if you don’t have at least a little weight to spare–which may in turn speed up certain other parts of aging, but there could be an additional effect on aging just from the presence of more cells in the body, each requiring additional metabolic processes to maintain.

Increased human height (due to better nutrition) over the past century could have a similar effect–shorter men do seem to live longer than taller men, eg: 

Observational study of 8,003 American men of Japanese ancestry from the Honolulu Heart Program/Honolulu-Asia Aging Study (HHP/HAAS), a genetically and culturally homogeneous cohort followed for over 40 years. …

A positive association was found between baseline height and all-cause mortality (RR = 1.007; 95% CI 1.003–1.011; P = 0.002) over the follow-up period. Adjustments for possible confounding variables reduced this association only slightly (RR = 1.006; 95% CI 1.002–1.010; P = 0.007). In addition, height was positively associated with all cancer mortality and mortality from cancer unrelated to smoking. A Cox regression model with time-dependent covariates showed that relative risk for baseline height on mortality increased as the population aged. Comparison of genotypes of a longevity-associated single nucleotide polymorphism in FOXO3 showed that the longevity allele was inversely associated with height. This finding was consistent with prior findings in model organisms of aging. Height was also positively associated with fasting blood insulin level, a risk factor for mortality. Regression analysis of fasting insulin level (mIU/L) on height (cm) adjusting for the age both data were collected yielded a regression coefficient of 0.26 (95% CI 0.10–0.42; P = 0.001).

The more of you there is, the more of you there is to age.

Interesting: lots of data on human height.

But there’s another possibility involving internal temperature–since internal body temperature requires calories to maintain, people who “run hot” (that is, are naturally warmer) may burn more calories and tend to be thinner than people who tend to run cool, who may burn fewer calories and thus tend to weigh more. Eg, low body temperature linked to obesity in new study: 

A new study has found that obese people (BMI >30) have lower body temperature during the day than normal weight people. The obese people had an average body temperature that was .63 degrees F cooler than normal weight people. The researchers calculated that this lower body temperature—which reflects a lower metabolic rate—would result in a body fat accumulation of approximately 160 grams per month, or four to five pounds a year, enough for the creeping weight gain many people experience.

There’s an interesting discussion in the link on thyroid issues that cause people to run cold and thus gain weight, and how some people lose weight with thyroid treatment.

On the other hand, this study found the opposite, and maybe the whole thing just washes out to women and men having different internal temperatures?

Obese people are–according to one study–more likely to suffer mood or mental disorders, which could also be triggered by an underlying health problem. They also suffer faster functional decline in old age:

Women had a higher prevalence of reported functional decline than men at the upper range of BMI categories (31.4% vs 14.3% for BMI > or =40). Women (odds ratio (OR) = 2.61, 95% confidence interval (CI) = 1.39-4.95) and men (OR = 3.32, 95% CI = 1.29-8.46) exhibited increased risk for any functional decline at BMI of 35 or greater. Weight loss of 10 pounds and weight gain of 20 pounds were also risk factors for any functional decline.

Note that gaining weight and losing weight were also related to decline, probably due to health problems that caused the weight fluctuations in the first place.

Of course, general physical decline and mental decline go hand-in-hand. Whether obesity causes declining health, declining health causes obesity, or some underlying third factor, like biological aging underlies both, I don’t know.

Anyway, I know this thought is a bit disjointed; it’s mostly just food for thought.

Open Thread: Hot Cocoa, Neanderthal Boats, Sadists and Incompetents

imagesIt’s been a slow week for comments, probably because everyone is still passed out/out of town/tired/sick/busy from all of the holiday revelry. Some of you are still celebrating. Still, I invite you all to come in, take a seat by the fire, pick up a warm mug of cocoa, and enjoy yourselves with some relaxing chat and mingle.

Anyone making New Years’ Resolutions?

Mine involve being more social in real life.

Some interesting links:

Role of Parenting in the Prediction of Criminal Involvement

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“Sadists” more likely to take “courageous” action against “injustice” on the internet:

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Could Neanderthals Build Boats?

But the stone tools on Naxos appeared to be hewn by Paleolithic people — much more ancient humans, perhaps not members of our species at all.

Since 2013, Carter has co-directed a new round of investigations on Naxos. He and a handful of others working in the region have begun to furnish evidence that humans reached the islands of the Aegean Sea 250,000 years ago and maybe earlier. If those dates are confirmed, it means the first people there were Neanderthals, their probable ancestors, Homo heidelbergensis or maybe even Homo erectus. …

Other researchers insist that much better evidence needs to be discovered to attribute such complex behaviours to Neanderthals and other hominins …

Then, in 1988, archeologists began excavating a collapsed rock shelter on the southern shore of Cyprus. They found about 1,000 bladelets and small tools typically associated with pre-Neolithic people.

“There was a lot of skepticism at first,” said Alan Simmons, an anthropologist at the University of Nevada Las Vegas who was involved in the work. “But once we had all the radiocarbon dates, it came to be accepted.”

The site pushed the peopling of Cyprus back to 12,000 years ago — only a few millennia, but enough to break the Neolithic barrier and establish the presence of hunter-gatherers. Today, the distance to mainland Turkey is about 75 kilometres. Sea levels have fluctuated and the crossing was once shorter, but Cyprus has always been an island.

The discoveries on Cyprus overturned the idea that hunter-gatherers were incapable or unwilling to travel by sea. But the debate was still confined to the activities of our species, Homo sapiens.

In 2008, a Greek-American team of archeologists began searching on the southwest coast of Crete for pre-Neolithic artifacts. They found many from roughly the same era as those on Cyprus. But they also found rough quartz hand axes and cleavers that appeared to be much more ancient.

The team discovered artifacts eroding out of a layer of soil that dated to at least 130,000 years ago, and the tools themselves looked like those archeologists associate with archaic hominin sites on the mainland — ones that are at least 250,000 years old. …

c0y7hezxeaa6akkFinally, a memorial fund for the wife and family of Polish truck driver Lukasz Urban, murdered in Germany 19th December 2016. Poor man, poor family.

On a related note, here’s an interesting quote about the importance of transparency to prevent government incompetence from Julian Assange of Wikileaks fame.

“Incompetence” murdered Kukasz Urban. Among many other things.

 

On to our Comments of the Week!

Unknown123 has contributed a couple of good comments to our discussion of race and crime:

“only about one-quarter of one percent (0.25 percent) of all whites will be violently victimized by a black person this year”

This would mean that its 2,5% every 10 years. A typical american white lives 80 years this would mean their lifelong chance of getting attacked by a black is 20%(!!!) exactly the same number they argue the chance of a women is to be raped in life. The same Tim Wise made a big deal of how high that is. Of course he takes anual number for other crime and lifelong numbers for rape.

And Race Realist contributed a fine post on correlations between weight and IQ:

Kanazawa (2014), reviewed the data on the research between obesity and IQ. What he found was that those studies that concluded that obesity causes lowered intelligence only observed cross-sectional studies. Longitudinal studies that looked into the link between obesity and intelligence found that those who had low IQs since childhood then became obese later in life and that obesity does not lead to low IQ. … He states that those with IQs below 74 gained 5.19 BMI points, whereas those with IQs over above 126 gained 3.73 BMI points in 22 years, which is a statistically significant difference. Also noted, was that those at age 7 who had IQs above 125 had a 13.5 percent chance of being obese at age 51, whereas those with IQs below 74 at age 7 had a 31.9 percent chance of being obese.

Thanks everyone, and keep up the good work/great comments!

Weight, Taste, and Politics: A Theory of Republican Over-Indulgence

So I was thinking about taste (flavor) and disgust (emotion.)

As I mentioned about a month ago, 25% of people are “supertasters,” that is, better at tasting than the other 75% of people. Supertasters experience flavors more intensely than ordinary tasters, resulting in a preference for “bland” food (food with too much flavor is “overwhelming” to them.) They also have a more difficult time getting used to new foods.

One of my work acquaintances of many years –we’ll call her Echo–is obese, constantly on a diet, and constantly eats sweets. She knows she should eat vegetables and tries to do so, but finds them bitter and unpleasant, and so the general outcome is as you expect: she doesn’t eat them.

Since I find most vegetables quite tasty, I find this attitude very strange–but I am willing to admit that I may be the one with unusual attitudes toward food.

Echo is also quite conservative.

This got me thinking about vegetarians vs. people who think vegetarians are crazy. Why (aside from novelty of the idea) should vegetarians be liberals? Why aren’t vegetarians just people who happen to really like vegetables?

What if there were something in preference for vegetables themselves that correlated with political ideology?

Certainly we can theorize that “supertaster” => “vegetables taste bitter” => “dislike of vegetables” => “thinks vegetarians are crazy.” (Some supertasters might think meat tastes bad, but anecdotal evidence doesn’t support this; see also Wikipedia, where supertasting is clearly associated with responses to plants:

Any evolutionary advantage to supertasting is unclear. In some environments, heightened taste response, particularly to bitterness, would represent an important advantage in avoiding potentially toxic plant alkaloids. In other environments, increased response to bitterness may have limited the range of palatable foods. …

Although individual food preference for supertasters cannot be typified, documented examples for either lessened preference or consumption include:

Mushrooms? Echo was just complaining about mushrooms.

Let’s talk about disgust. Disgust is an important reaction to things that might infect or poison you, triggering reactions from scrunching up your face to vomiting (ie, expelling the poison.) We process disgust in our amygdalas, and some people appear to have bigger or smaller amygdalas than others, with the result that the folks with more amygdalas feel more disgust.

Humans also route a variety of social situations through their amygdalas, resulting in the feeling of “disgust” in response to things that are not rotten food, like other people’s sexual behaviors, criminals, or particularly unattractive people. People with larger amygdalas also tend to find more human behaviors disgusting, and this disgust correlates with social conservatism.

To what extent are “taste” and “disgust” independent of each other? I don’t know; perhaps they are intimately linked into a single feedback system, where disgust and taste sensitivity cause each other, or perhaps they are relatively independent, so that a few unlucky people are both super-sensitive to taste and easily disgusted.

People who find other people’s behavior disgusting and off-putting may also be people who find flavors overwhelming, prefer bland or sweet foods over bitter ones, think vegetables are icky, vegetarians are crazy, and struggle to stay on diets.

What’s that, you say, I’ve just constructed a just-so story?

Well, this is the part where I go looking for evidence. It turns out that obesity and political orientation do correlate:

Michael Shin and William McCarthy, researchers from UCLA, have found an association between counties with higher levels of support for the 2012 Republican presidential candidate and higher levels of obesity in those counties.

Shin and McCarthy's map of obesity vs. political orientation
Shin and McCarthy’s map of obesity vs. political orientation

Looks like the Mormons and Southern blacks are outliers.

(I don’t really like maps like this for displaying data; I would much prefer a simple graph showing orientation on one axis and obesity on the other, with each county as a datapoint.)

(Unsurprisingly, the first 49 hits I got when searching for correlations between political orientation and obesity were almost all about what other people think of fat people, not what fat people think. This is probably because researchers tend to be skinny people who want to fight “fat phobia” but aren’t actually interested in the opinions of fat people.)

The 15 most caffeinated cities, from I love Coffee
The 15 most caffeinated cities, from I love Coffee–note that Phoenix is #7, not #1.

Disgust also correlates with political belief, but we already knew that.

A not entirely scientific survey also indicates that liberals seem to like vegetables better than conservatives:

  • Liberals are 28 percent more likely than conservatives to eat fresh fruit daily, and 17 percent more likely to eat toast or a bagel in the morning, while conservatives are 20 percent more likely to skip breakfast.
  • Ten percent of liberals surveyed indicated they are vegetarians, compared with 3 percent of conservatives.
  • Liberals are 28 percent more likely than conservatives to enjoy beer, with 60 percent of liberals indicating they like beer.

(See above where Wikipedia noted that supertasters dislike beer.) I will also note that coffee, which supertasters tend to dislike because it is too bitter, is very popular in the ultra-liberal cities of Portland and Seattle, whereas heavily sweetened iced tea is practically the official beverage of the South.

The only remaining question is if supertasters are conservative. That may take some research.

Update: I have not found, to my disappointment, a simple study that just looks at correlation between ideology and supertasting (or nontasting.) However, I have found a couple of useful items.

In Verbal priming and taste sensitivity make moral transgressions gross, Herz writes:

Standard tests of disgust sensitivity, a questionnaire developed for this research assessing different types of moral transgressions (nonvisceral, implied-visceral, visceral) with the terms “angry” and “grossed-out,” and a taste sensitivity test of 6-n-propylthiouracil (PROP) were administered to 102 participants. [PROP is commonly used to test for “supertasters.”] Results confirmed past findings that the more sensitive to PROP a participant was the more disgusted they were by visceral, but not moral, disgust elicitors. Importantly, the findings newly revealed that taste sensitivity had no bearing on evaluations of moral transgressions, regardless of their visceral nature, when “angry” was the emotion primed. However, when “grossed-out” was primed for evaluating moral violations, the more intense PROP tasted to a participant the more “grossed-out” they were by all transgressions. Women were generally more disgust sensitive and morally condemning than men, … The present findings support the proposition that moral and visceral disgust do not share a common oral origin, but show that linguistic priming can transform a moral transgression into a viscerally repulsive event and that susceptibility to this priming varies as a function of an individual’s sensitivity to the origins of visceral disgust—bitter taste. [bold mine.]

In other words, supertasters are more easily disgusted, and with verbal priming will transfer that disgust to moral transgressions. (And easily disgusted people tend to be conservatives.)

The Effect of Calorie Information on Consumers’ Food Choice: Sources of Observed Gender Heterogeneity, by Heiman and Lowengart, states:

While previous studies found that inherited taste-blindness to bitter compounds such
as PROP may be a risk factor for obesity, this literature has been hotly disputed
(Keller et al. 2010).

(Always remember, of course, that a great many social-science studies ultimately do not replicate.)

I’ll let you know if I find anything else.

Further implications of hippocampal theory

So while on my walk today, I got to thinking about various potential implications of the hippocampal theory of time preference.

The short version if you don’t want to read yesterday’s post is that one’s degree of impulsivity/ability to plan / high or low time preference seems to be mediated by an interaction between the nucleus accumbens, which seems to a desire center, and the hippocampus, which does a lot of IQ-related tasks like learn new things and track objects through space. Humans with hippocampal damage become amnesiacs; rats with the connection between their nucleus accumbens and hipocampus severed lose their ability to delay gratification even for superior rewards, becoming slaves to instant gratification.

So, my suspicion:

Relatively strong hippocampus => inhibition of the nucleus accumbens => low time preference.

Relatively weak hippocamus => uninhibited nucleus accumbens => high time preference (aka impulsivity.)

Also, Strong hippocampus = skill at high IQ tasks.

Incentivise traits accordingly.

Anyway, so I was thinking about this, and it occurred to me that it could explain a number of phenomena, like the negative correlation between weight and IQ, eg:

Shamelessly stolen from Jayman's post.
Shamelessly stolen from Jayman’s post. As usual, I recommend it.

(Other theories on the subject: Intelligent people make lots of money and so marry attractive people, resulting in a general correlation between IQ and attractiveness; there is something about eating too much or the particular foods being eaten that causes brain degeneration.)

People generally claim that overweight people lack “willpower.” Note that I am not arguing about willpower; willpower is only a tiny part of the equation.

The skinny people I know do not have willpower. They just do not have big appetites. They are not sitting there saying, “OMG, I am so hungry, but I am going to force myself not to eat right now;” they just don’t actually feel that much hunger.

The fat people I know have big appetites. They’ve always had big appetites. Some of them have documented large appetites going back to infancy. Sure, their ability to stay on a diet may be directly affected by willpower, but they’re starting from a fundamentally different hunger setpoint.

So what might be going on is just a matter of whether the hippocampus or nucleus accumbens happens to be dominant. Where the NE is dominant, the person feels hunger (and all desires) quite strongly. Where the hippocampus is dominant, the person simply doesn’t feel as much hunger (or other desires.)

That a strong hippocampus also leads to high IQ may just be, essentially, a side effect of this trade-off between the two regions.

We might expect, therefore, to see higher inhibition in smart people across a range of behaviors–take socializing, sex, and drug use. *Wanders off to Google*

So, first of all, it looks like there’s a study that claims that higher IQ people do more drugs than lower IQ people. Since the study only looks at self-reported drug use, and most people lie about their illegal drug use, I consider this study probably not very useful; also, drug use is not the same as drug addiction, and there’s a big difference between trying something once and doing it compulsively.

Heroin and cocaine abusers have higher discount rates for delayed rewards than alcoholics or non-drug-using controls

IQ and personality traits assessed in childhood as predictors of drinking and smoking behaviour in middle-aged adults: a 24-year follow-up study (they found that lower IQ people smoke more)

Severity of neuropsychological impairment in cocaine and alcohol addiction: association with metabolism in the prefrontal cortex (Cocaine users are dumb)

HighAbility: The Gifted Introvert claims that 75% of people over 160 IQ are introverts.

Research Links High Sex Drive To High IQ, But Brainiacs Still Have Less Sex Than Everyone Else (Spoiler alert: research does not link high sex drive to IQ. Also, NSFW picture alert.)

I am reminded here of a story about P. A. M. Dirac, one of my favorite scientists:

“An anecdote recounted in a review of the 2009 biography tells of Werner Heisenberg and Dirac sailing on an ocean liner to a conference in Japan in August 1929. “Both still in their twenties, and unmarried, they made an odd couple. Heisenberg was a ladies’ man who constantly flirted and danced, while Dirac—’an Edwardian geek’, as biographer Graham Farmelo puts it—suffered agonies if forced into any kind of socialising or small talk. ‘Why do you dance?’ Dirac asked his companion. ‘When there are nice girls, it is a pleasure,’ Heisenberg replied. Dirac pondered this notion, then blurted out: ‘But, Heisenberg, how do you know beforehand that the girls are nice?'”[30]” (from the Wikipedia.)

Folks speculate that Dirac was autistic; obviously folks don’t speculate such things about Heisenberg.

Autism I have previously speculated may be a side effect of the recent evolution of high math IQ, and the current theory implies a potential correlation between various ASDs and inhibition.

Looks like I’m not the first person to think of that: Atypical excitation–inhibition balance in autism captured by the gamma response to contextual modulation:

The atypical gamma response to contextual modulation that we identified can be seen as the link between the behavioral output (atypical visual perception) and the underlying brain mechanism (an imbalance in excitatory and inhibitory neuronal processing). The impaired inhibition–excitation balance is suggested to be part of the core etiological pathway of ASD (Ecker et al., 2013). Gamma oscillations emerge from interactions between neuronal excitation and inhibition (Buzsaki and Wang, 2012), are important for neuronal communication (Fries, 2009), and have been associated with e.g., perceptual grouping mechanisms (Singer, 1999).

Also, Response inhibition and serotonin in autism: a functional MRI study using acute tryptophan depletion:

“It has been suggested that the restricted, stereotyped and repetitive behaviours typically found in autism are underpinned by deficits of inhibitory control. … Following sham, adults with autism relative to controls had reduced activation in key inhibitory regions of inferior frontal cortex and thalamus, but increased activation of caudate and cerebellum. However, brain activation was modulated in opposite ways by depletion in each group. Within autistic individuals depletion upregulated fronto-thalamic activations and downregulated striato-cerebellar activations toward control sham levels, completely ‘normalizing’ the fronto-cerebellar dysfunctions. The opposite pattern occurred in controls. Moreover, the severity of autism was related to the degree of differential modulation by depletion within frontal, striatal and thalamic regions. Our findings demonstrate that individuals with autism have abnormal inhibitory networks, and that serotonin has a differential, opposite, effect on them in adults with and without autism. Together these factors may partially explain the severity of autistic behaviours and/or provide a novel (tractable) treatment target.”

This may not have anything at all to do with the hippocampus-NA system, of course.

Schizophrenic patients, on the other hand, appear to have the opposite problem: Hyper Hippocampus Fuels Schizophrenia?:

““What we found in animal models and others have found postmortem in schizophrenic patients is that the hippocampus is lacking a certain type of GABA-ergic [GABA-producing] neuron that puts the brakes on the system,” says Grace. “What we’re trying to do is fix the GABA system that’s broken and, by doing that, stabilize the system so the dopamine system responses are back to normal, so that we can actually fix what’s wrong rather than trying to patch it several steps downstream.””

Wow, I made it through two whole posts on the brain without mentioning the amygdala even once.

Has eliminating hookworms made people fatter?

Okay, yes, obviously when you take the gut parasites out of people, they tend to gain weight immediately after. That’s not exactly what I’m talking about.

First, let’s assume you come from a place where humans and hookworms have co-existed for a long, long time. The hookworms that just about everybody in the American South used to have appear to have come from Africa, so I think it safe to assume that hookworms have probably been infecting a lot of people in Africa for a long time. I don’t know how long–could be anywhere from a few hundred years, if they’d come from somewhere else or recently mutated or something, or could be tens of thousands or hundreds of thousands of years, if they’ve just always been hanging around. Let’s just go with tens of thousands, because if it wasn’t them, it was probably something else.

Over a few thousand years of constant infection, you’d expect to develop some sort of biological response to minimize the chances of death–that is, your ancestors would have evolved over time to be less susceptible to the parasite. Obviously not getting the parasite is one great way to avoid getting killed by it, but let’s assume that’s not an option.

Another solution would be to just absorb food differently–faster, say, or in a manner that circumvents the parts of the gut that are normally infected. Over time, humans and parasites might tend toward an equilibrium–humans stepping up their digestion to make up for what’s lost to the parasite.

Remove the parasite, and equilibrium is lost: suddenly the human starts gaining a lot of weight, especially compared to people from populations that did not adapt to the parasite.

That functional a gut isn’t needed anymore, but it might persist for a while if there are no counter-evolutionary pressures.

Just about the best thing I could find today (light and BMI):

“The results of this study demonstrate that the timing of even moderate intensity light exposure is independently associated with BMI. Specifically, having a majority of the average daily light exposure above 500 lux (MLiT500) earlier in the day was associated with a lower BMI. In practical terms, for every hour later of MLiT500 in the day, there was a 1.28 unit increase in BMI. The complete regression model (MLiT500, age, gender, season, activity level, sleep duration and sleep midpoint) accounted for 34.7% of the variance in BMI. Of the variables we explored, MLiT500 contributed the largest portion of the variance (20%).”

From “Timing and Intensity of Light Correlate with Body Weight in Adults” by Kathryn J. Reid, Giovanni Santostasi, Kelly G. Baron, John Wilson, Joseph Kang, and Phyllis C. Zee.