Lead Pollution Reduced the Intelligence of Europeans

Are we more intelligent than our ancestors? Surely you have asked yourself this on several occasions. A priori, everything points to yes. Technological advances, in medicine, in space technology… in short, the 21st century opens with countless new developments that make us think that yes, our IQ is indeed higher than that of our ancestors.

However, a recent study refutes this idea. And the research, recently published in the journal Proceedings of the National Academy of Scienceshas shown that, Since the Romans, the IQ (intelligence quotient) of Europeans has fallen by 2.5 – 3 points, and everything indicates that it is due to lead contamination through inhalation.

Lead contamination in Europeans: the secret is in Greenland

The team of researchers, led, among others, by Joseph R. McConnell (Desert Research Institute, Reno), have analyzed ice sheets from Greenland that correspond to the Roman period in Europe. In them, they have found obvious traces of high levels of lead, which European settlers inhaled and from which they suffered high contamination. How did lead levels get so high? McConnell’s team links the discovery to Roman silver mines and smelters.

Historically, it is known that the Romans carried out important mining activity throughout Europe, so it is not unreasonable to propose that it was precisely this dynamism in mining that caused notable air pollution that reached the entire continent.

The unquestionable fact that lead reached a region as remote as Greenland is suggestive enough to conclude that Pollution reached all parts of the Roman Empire with the consequences that this had for its inhabitants.

Poison in the blood

Research in modern populations shows how highly dangerous lead can be for health. It is a neurotoxin that can cause severe alterations, such as cognitive disabilities, mental disorders and even infertility problems.

Actually, Any human bloodstream contains lead, but if levels exceed 3.5 µg/dL immediate testing is required.. The presence of high amounts of lead in the body is highly toxic and constitutes a true poison in the blood, which then distributes it to all parts of the body.

We tend to think that pollution is a thing of modernity, but the fact is that reliable evidence has been found that lead pollution has been present since human beings began their productive activity. The case of Ludwig van Beethoven is well known: after analyzing his hair, high amounts of lead and mercury were found, surely caused by the contamination of Danube fish.

But, beyond the various health problems it entails, can lead contamination reverse the growth of human IQ or intellectual quotient?

A little less intelligent than the Romans

The study concludes that, indeed, increased lead levels and decreased IQ may be related. Lead exposure levels at the time of the Pax Romana (that is, between 27 BC and 180 AD) turned out to be incredibly high: a full third of what they were in the United States during the 1970s. More yet: according to McConnell, American children today are not exposed to as much lead as the inhabitants of the Roman Empire…

But how is it possible that so much lead was emitted in Roman times? The researcher is clear in this sense: for each ounce of silver, approximately 10,000 ounces of lead were produced, so, while the Romans manufactured the desired silver, they were introducing a large amount of lead into the atmosphere, which they subsequently inhaled.

This inhalation produced, according to the study, a significant recession in the IQ of Europeans. Specifically, The inhabitants of ancient Hispania are the ones who come out worst off. Well, according to McConnell, by living near the most important mines, they are the ones who breathed the most amounts of lead. On the other hand, it is also necessary to take into account other sources of contamination, such as, for example, “poisoned” wine, in which lead was leached from the containers.

The fall of the Roman empire… due to lead?

Some researchers go further and issue conclusions that cannot help but sound somewhat sensational. And certain scholars in the 1980s admitted that lead had a lot to do with the fall of the Roman Empire, by poisoning and alienating Roman elites.

Of course, this is saying a lot, and, above all, it is ignoring all the rest of the circumstances that led to the fall of the empire. In other words, it is a reductionism that, because it is so simple, is absurd. Because, if lead had been capital in disintegrating the empire, it would also have been capital in the case of subsequent empires, exposed to the same levels of lead as their predecessors.

The exact relationship between lead poisoning among the Romans (whose high levels have been sufficiently demonstrated) and the decline in the IQ of the European population over 2,000 years of history remains to be confirmed. The study is still open.