Parasites may explain regional differences in intelligence | Hacker News Reader

Parasites may explain regional differences in intelligence

economist.com

38 pointsRob-Goodier33 comments

When looking at correlating factors, they should also include diet. I remember reading that some Central Asian countries, as recently as a decade ago, were losing more than 5 IQ points on average just to iodine deficiency.

Another HN participant told me about a reply to this latest paper by these authors.

http://blogs.discovermagazine.com/notrocketscience/2010/06/2...

When I see gee-whiz news reports about science, even in very reputable publications like The Economist, I think to turn to Peter Norvig's article "Warning Signs in Experimental Design and Interpretation"

http://norvig.com/experiment-design.html

to evaluate the research.

There is an interesting comment in the Discover post, where Carl Zimmer (author of popular science book on parasites) points out several studies from all around the world (Jamaica, China, Indonesia, Philippines) where they found children got smarter after de-worming:

http://blogs.discovermagazine.com/notrocketscience/2010/06/2...

Why wouldn't it simply be the case that more intelligent societies have been more successful at eradicating disease?

My first thought: which parasites make you smarter?

Had the same thought, though the article says that the lack of infectious disease (parasites) would cause intelligence gain. The population of countries where disease is less of a problem wouldn't see the same benefit...

Me too. Although, then we'd probably call that relationship symbiotic and not parasitic.

A local political establishment which will subsidize your technical education so that you can develop improved weapons systems?

The first thing I thought of is that if lack of diseases is what has been causing the rise in intelligence, then there's likely to be a ceiling that average intelligence will hit as countries become healthier, rather than some mysterious force continually increasing average intelligence forever. That makes me a little sad.

I'm really curious as to how exactly they accounted for other factors. They say they compared findings to other studies that looked at other possible explanations, but quite many of them are certainly correlated if not caused by one another.

one can deduce how two kinds of organisms have influenced each other by studying how their respective gene pools (have) co-evolve(d)

Statically the problem that he posed is still there, what are the variables they ignored when calculating the statistical significance of their hypothesis? I actually read the paper, and well, it was one of the worst that I have read in my entire life. In the end of the paper they wrote: "We are not arguing that global variation in intelligence is only caused by parasite stress."

So why is the point of having a research about causation when various independent causes can exist and do not test how much the hypothetical cause affects the causation relationship in general? Should I publish a paper on intelligence and ice cream consumption by population in the last 50 years to show how ridiculous the entire situation is?

Sounds like that sort of paper that someone publishes only so that his name get cited more times.

It's politically illegal to say that on average whites are smarter than blacks so instead they have this little gem:

"....distance from humanity’s African homeland (novel environments could encourage greater intelligence)...."

There are plenty of Blacks outside Africa and I hear that in South Africa there are loads of whites.

If you look at the data you'll notice it's very noisy. And I bet the noise is entirely (or mostly) made up of race.

Note that one of the things they did not control for was race.

It's racist to say this, I know, and more importantly it's not nice. But if you are going to make a study, you have to deal with reality.

Control for race, and then check the correlation with parasites.

How do you control for race? My grandmother is Mexican. My grandfather is German. What "race" is my mom? What about me?

You do the best you can. Perfection is not required.

If you control for race you are implying that there are racial differences. That, may or may not be true, most likely it is not true. Social sciences are adverse to rigorously investigate the issue because I think we have learned from the last century some fundamental things, the main one being that labelling an entire race as inferior is extremely dangerous.

Besides, I am sure all races are infected by diseases and so too I am sure that the difference the further you go from Africa is not because of ones race but because societies are richer the further you go and thus have better sanitation. Moreover, I think that the unites states contains more black individuals than Europe, thus, if race had any effect, you would expect Europe to be more intelligent.

Not that we in Europe aren't mind you :P

How would you even define "race"? Does the concept as used in the common socio-cultural context have any consistent meaning with respect to physiology? If so, how would you measure it?

Being a member of a category isn't an inherent property of an individual thing; rather, including a specified set of individuals is what defines the category. If you try to study a phenomenon in general, but with preconceived notions about how each individual subject should be categorized, you're skewing your results straight from the outset.

another reason to support universal health care: a smarter public

You presume that universal health care will lead to a healthier public

It's been successful in every country that has tried it. Granted, the US has a bad habit of poorly implemented government programs so who knows, we may be the first exception.

PS: Medical outcomes are far more dependent on the average level of care than the peek level of care. EX: There is a lot of evidence that the average doctor is significantly more effective than a "high preforming" doctor that is sleep deprived.

> It's been successful in every country that has tried it.

Doesn't that depend on the starting point? For example, NHS started during the post WWII depression in the UK. The US isn't starting from there.

I'm trying to track down the stats, but I've heard that the US lifespan is world-longest if you adjust for accidents and homicide, two things that aren't affected by healthcare.

> Granted, the US has a bad habit of poorly implemented government programs so who knows, we may be the first exception.

The US govt gets the same amount of tax revenue per person as the "rich" EU countries. If the benefits are less ....

> I've heard that the US lifespan is world-longest if you adjust for accidents and homicide, two things that aren't affected by healthcare.

Other measures of health care quality, such as infant mortality, are worse in the US than in many other countries. So I doubt it.

Other measures of health care quality, such as infant mortality, are worse in the US...

Nope. The US spends far more on trying to save the lives of premature and sickly newborns than any other country. Many these don;t make it after being born and show up in the stats as "high infant mortality". This approach also drives up health care costs.

One can argue (having met two crack babies that survived, I personally would be tempted to in many cases) that US hospitals shouldn't do this, but nevertheless they do do it. And it costs money and skews statistics.

I also have personally experienced health care in other countries (Greece, Mexico, China -- where my wife was a doctor). No thanks.

The US spends far more on trying to save the lives of premature and sickly newborns than any other country.

[citation needed]

Many these don;t make it after being born and show up in the stats as "high infant mortality".

That's true in every country, regardless of how hard you try to save their lives. More of them make it after being born if you try very hard to save their lives.

I also have personally experienced health care in other countries (Greece, Mexico, China

So have I. I surely don't need to point out to you, with your wide travel experience, that not all other countries are equal. The Argentine health care I've experienced is head and shoulders above anything I've experienced in the US, although that's mostly because I live in the capital where things are good.

The US's infant mortality rate is about .0063. Greece's is about .005 to .007. Mexico's is .017 or .018. China's is about .020 to .023. Your personal experience that care is much worse in those countries, with the exception of Greece, supports the validity of infant mortality as a measure of care quality; it does not undermine it.

There are around 25 countries with better infant mortality than the US, but that doesn't include the three you listed. Several of them have less than half the infant mortality level of the US. Have you personally experienced health care in any of them? What was your experience?

https://secure.wikimedia.org/wikipedia/en/wiki/List_of_count...

I recognize that statistics do not always capture the reality of a situation. However, in this case, I don't think it's adequate to simply deny their validity without any evidence. (The evidence you have adduced so far, from your personal experience, supports their validity rather than undermining it.)

> There are around 25 countries with better infant mortality than the US,

With comparable populations?

For example, Scandanavians do well everywhere. (However, the US ones do better than the ones who didn't leave.) A population dominated by Scandanavians will do better than one that is more "typical".

I'm pretty sure that the US healthcare system is not responsible for crank and crack mothers, but it gets "credit" for their birth problems.

Much of that gap is, DoD spending and interest on debt. However, per person Canada spends about the same money on universal heath care as we do to cover 50% of heath care spending. Much of that relates to malpractice insurance, the overhead from private insurance/medical billing, and higher doctor salaries. But, we also pay a lot more for the same medications/medical devices etc.

So, looking at our "overhead" it's easy to see why we get little benefit from the money spent.

> "...if you adjust for accidents and homicide, two things that aren't affected by healthcare."

Healthcare is quite involved in dealing with the effects of accidents on humans. So I would think that death rate from accidents, broadly speaking, is not independent from level of healthcare. Or is that a technical term that already distinguishes between those that survive the accident long enough to possibly receive treatment and those that don't?

> So I would think that death rate from accidents, broadly speaking, is not independent from level of healthcare.

There are two numbers - the accident rate, which is independent of healthcare, and the "how good was treatment for accident victims" number, which does depend on healthcare. Their product is the death rate from accidents.

Here are two populations that demonstrate these effects.

In population 1, everyone has an accident each year and 90% survive. That's 10% deaths due to accidents.

In population 2, 10% of the population has an accident, and only 50% of accident victims survive. That's 5% deaths due to accidents.

If the accidents are the same, it's silly to argue that population 2 has better "accident healthcare" even though its death rate due to accidents is half of population 1's.

If the accidents are different, it's impossible to say which population has better accident healthcare without more information.

Here's another way to look at it. The death rate for automobile accidents in 2000 in the US was significantly higher than the death rate for automobile accidents in 1850. Does that imply that 1850 accident healthcare was better?

This article seems to be leading to the conclusion that basic healthcare helps eliminate the sort of diseases that contribute to a lower IQ population. These are probably people who lack very basic healthcare and sanitation... I think that it's hard to argue that the basic health needs of the population wouldn't be better served if it was health care was free (such as dealing with treatable communicable disease). I think you might run into problems if you're talking about specialist care, but otherwise.....

Correlation <> causation. IMHO they should be very careful before establishing a link between those two.

You should read the article. They considered that.

The correlation is about 67%, and the chance that it might have come about at random is less than one in 10,000. But correlation is not causation, so Mr Eppig and his colleagues tried to eliminate other possible explanations. Previous work has offered income, education, low levels of agricultural labour (which is replaced by more mentally stimulating jobs), climate (the challenge of surviving cold weather might provoke the evolution of intelligence) and even distance from humanity’s African homeland (novel environments could encourage greater intelligence) as explanations for national differences in IQ. However, all of these, except perhaps the last, are also likely to be linked to disease and, by careful statistical analysis, Mr Eppig and his colleagues show that all of them either disappear or are reduced to a small effect when the consequences of disease are taken into account.

There is, moreover, direct evidence that infections and parasites affect cognition. Intestinal worms have been shown to do so on many occasions. Malaria, too, is bad for the brain. A study of children in Kenya who survived the cerebral version of the disease suggests that an eighth of them suffer long-term cognitive damage. In the view of Mr Eppig and his colleagues, however, it is the various bugs that cause diarrhoea which are the biggest threat. Diarrhoea strikes children hard. It accounts for a sixth of infant deaths, and even in those it does not kill it prevents the absorption of food at a time when the brain is growing and developing rapidly.

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