Parasites may explain regional differences in intelligence

Parasites may explain regional differences in intelligence(economist.com)

38 points by Rob-Goodier 15 years ago | 33 comments

donaldc 15 years ago |

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.

tokenadult 15 years ago |

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.

bd 15 years ago | |

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...

anonymousDan 15 years ago |

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

T_S_ 15 years ago |

My first thought: which parasites make you smarter?

misterbwong 15 years ago | |

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...

joubert 15 years ago | |

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

gojomo 15 years ago | |

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

JeffL 15 years ago |

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.

diziet 15 years ago |

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.

joubert 15 years ago | |

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

zppx 15 years ago | | |

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.

ars 15 years ago |

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)...."

Ardit20 15 years ago | |

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

ars 15 years ago | | |

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.

awongh 15 years ago |

another reason to support universal health care: a smarter public

ams6110 15 years ago | |

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

Retric 15 years ago | | |

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.

awongh 15 years ago | | |

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.....

archer 15 years ago |

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

Dove 15 years ago | |

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.