Mailbag: Water Fluoridation and Human Genetic Variation

It is time for another entry in the mailbag series where I answer feedback email from readers and others. If you want to send me a question, comment or any other kind of feedback, please do so using the contact info on the about page.

Fluoride occurs naturally in many forms of drinking water, because it is leached from the bedrock where it occurs in the form of calcium fluoride and other compounds. Sometimes, fluoride is added into the drinking water where this natural source does not exist or is too little. Water fluoridation in drinking water prevents cavities (and contributes to equalizing dental health across socioeconomic groups), but the concentration is not large enough to cause harm.

There is an important limitation with water fluoridation, and that is that it is typically applied in an one-size-fits-all instead of tailoring the amount to the needs of the community. However, the objections to water fluoridation that you might find on the Internet and social media in particular is batshit conspiracy theories that water fluoridation sterilizes people and lowers their IQ despite the fact that the human populations has exploded in size during the past 100 years and IQ steadily rises over time due to the Flynn effect. Earlier, Debunking Denialism published a refutation of the claim that if you add fluoride, you should supposedly have no problem adding arsenic. This is, of course, completely wrong in so many different ways.

The second topic in this mailbag is that of human genetic variation. These issues are often misunderstood by so-called race realist who argues that modern genomics have validated pseudoscientific superstitions about human diversity from the 1700s. Why race realists are mistaken on the facts was discussed in Modern High-Throughput Genomics Versus Race Realism and dozens other on this websites.

But first, let us see what people have written in about water fluoridation.

Pete writes:

“Water fluoridation does not treat or cure anything.” yes that is accurate . After 70 years of fluoridation tooth decay is still rampant. In fact many non-fluoridated countries have better teeth than fluoridated countries. Fluoridation is the biggest scam of the 20th and 21st centuries.

Here Pete has decided to quote me out of context. The actual quote in the fluoridate article I linked above was “Water fluoridation does not treat or cure anything. Therefore, it is not a medication. One wonders why anti-fluoridation activists are not against naturally occurring fluoride in water, fluoride in tea or chlorination of drinking water.” In other words, this was part of an argument on why water fluoridation is not a form of mass medication. Water fluoridation does treat or cure anything, but it does prevent dental cavities. References to the scientific literature can be found in the original post.

The reason that tooth decay is still rampant is that people consume high quantities of sugar than before and that people do not use toothpaste and fluoridated mouthwash enough. It isn’t enough to drink fluoridated drinking water to avoid cavities if you skip the toothbrush and eat an excessive amount of sugary food all around the clock. Pete has simply not factored in the obesity crisis.

Another critic of water fluoridation with the name of Dan wrote the following:

Anyone who can’t understand that fluoridationism is based on pure pseudoscience is extremely stupid. You wrote “arbitrary correlations do not demonstrate causation”. That is true, but somehow you have failed to recognise that the “studies” which are supposed to prove that forced-fluoridation prevents dental cavities depend on the fallacy that correlation proves causation. The fact is you can’t cite a single good quality original research study which indicates that the forced-fluoridation human experiment is anything but harmful and useless. You freaks are the world’s ultimate hypocrites.

Here, Dan attempts to pull down the science of water fluoridation down to the level of pseudoscience by calling it an “ism”. In reality, many studies (reviewed here and here) have shown that water fluoridation works and both the CDC and the WHO supports this conclusion. WHO even calls it “the most effective public health measure for the prevention of dental decay.”. As can be read above, the efficacy of water fluoridation is not based on correlations only. There are many other study designs and indirect evidence, as well as the fact that the mechanisms by which water fluoridation works have been identified. Had Dan read the original post, he would have noticed that the review papers I cited did, by definition, cite good quality original research. Furthermore, water fluoridation is not forced, since you are free not to drink tap water.

Moving on to human genetic variation, a commenter by the name of Curious sent in what he or she thought were four rhetorical “gotcha” questions:

1) Japan for Japanese, Africa to Africans but white countries for everyone? Why?
2) If races only have a small % of difference, why isn’t this important. We have a 2% different with chimps. Why doesn’t that small % explain differences in IQ by race as well as th differences in skin/hair?
3) Why is the % of white people lowering compared to other races?
4) Why are white nations more successful, have better technology, were able to take over other nations, and have lower poverty, better systems etc? While black countries never had any industrial revolution and most of them are living in mud huts, have lower national IQ etc?

The first question is not so much a scientific question, but rather a common white nationalist talking-point. The answer is that Japan is going to experience one of their largest demographic crisis ever in a few decades due to the fact that they have very little immigration, low and decreasing fertility and people reducing their sexual activity generally. So Japan is probably going to need quite a lot of immigration if they want to keep their current living standards. There are also racism in Japan, notably against Koreans and the Burakumin. If someone wants to move from Europe to Africa, I think they should have the freedom to do so if they want.

The second question does not completely appreciate scale. The average difference (the same kind of differences as the ~2% figure cited above) between two people is 0.1%. Only a tiny proportion of this, perhaps 10%, is between continents, so that might be on the order of 0.01%. So the difference, and the answer to the first part of the question, is that the difference is two orders of magnitude lower, and one order of magnitude lower than between individuals. In essence, it is like asking why a bridge across a large river cannot be 1 meter when there are bridges that are 100 meters hat do cross rivers. It is a misunderstanding of scale. Why cannot these 0.01% genetic variation between continents account for unadjusted IQ differences? That is because the vast majority of genes that have undergone recent differential positive selection have little or nothing to do with IQ, but more to do with gross morphology and the immune system. Sources can be found in the original post about human genetic variation linked above.

The third question assumes typological (rather than population thinking) and blending inheritance. In other words, they think that an offspring between a “white” and a “black” parent is “black” (or at any rate “non-white”). But this is not how it works. That person has just as many gene variants from the “white” parent and the “black” parent. Because inheritance is discrete and not blending, the notion that you are “mixing out whiteness” over time is not scientific accurate.

The fourth question neglects history, development and geography. There are many times throughout history when Europeans have been living in very rudimentary housing and other cultures have intellectually and technologically flourished. In particular, ancient Egyptians and the Chinese empire were far superior to Europeans during certain time periods. It is also no longer accurate to describe Africans as categorically living in mud huts, because there has been an immense development during the past 50 years and Africa already have several megacities, such as Cairo and Lagos, and they will have many more in the near future due to massive urbanization. Global poverty has declined to below 10% in recent decades.

Another factor to take into account is geography. Europe is in temperate climate, whereas Africa is in tropical or subtropical climate. Europe is also wide, so crops that worked well in one area of Europe can work well in other areas as well compared with crops in different parts of Africa. There are many other geographical factors that have played a role historically and those are reviewed in the original post linked above. On the issue of national IQ, most of those studies do not use representative samples (and in some comparisons, adults are compared with children) and over 100 countries (>50% of the dataset) has been interpolated from neighbors because there is no data. Malnutrition also has a severe effect on IQ, so those studies do not generally control sufficiently for confounders. These issues about IQ studies are discussed in additional detail here.