More compelling evidence in favor of hereditarianism??

 That is, of a postmodern "heresy": believing that behavior is primarily determined by genetics or biology, not by environment.

1- On the alleged absolute causal relationship between low cognitive performance and social deprivation

"Sub-Saharan Africans are, on average, less intelligent in terms of IQ and other comparative aspects of intelligence because of the very high rates of poverty they experience or the social neglect in which they live. Because malnutrition and poverty directly affect brain development, all that is needed is for these differences in intellectual performance to be eliminated."

This is certainly a line of thinking commonly adopted by individuals who identify with the "left" of the political-ideological spectrum, and it applies not only to the sub-Saharan context, but also to any other context of poverty and inequality. More than a thought, it is a narrative, a discourse closed to intellectually honest criticism and that typically does not accurately reflect the facts. While it makes logical sense that poor environmental conditions have deleterious medium- to long-term effects on humans, their effects were not well understood until now, especially without examples of significant social improvements some 70 or 80 years ago. But in 2025, this assertion is no longer possible, given that such examples already exist, as in the case of the United States, a country that, while in the 1940s had high levels of social inequality and a significant proportion of individuals living in absolute poverty, has managed to significantly reduce its extreme poverty statistics to this day, also because it has managed to provide the majority of its citizens with a life cycle free from malnutrition. For one of the most obese countries in the world today, it is clear that this situation of endemic hunger, especially for certain ethnic, racial, and social groups, is a thing of the past. It's not that it will definitely not return, but for a good few decades now, there has been significant improvement in the reduction of extreme poverty there. As a result, Americans, even the poorest, have, over the generations, become taller and more robust than their grandparents and great-grandparents. However, average differences in cognitive performance and social adjustment continue to persist, even though most Americans do not live in an intergenerational cycle of malnutrition and measures to combat inequalities (regardless of how fair they may be) have been adopted. This is a supposed paradox, because if better nutrition promotes the healthy development of body and mind, and this is primarily true for the body, the belief that it _works miracles_ for the mind or brain seems to be untenable, at least based on this remarkable evidence from the richest country in the world, with a high rate of social and racial inequalities, especially some 70 years ago, where, in fact, there has been a secular and cumulative increase in the height and weight of its inhabitants, gains particularly strong among the poorest, due to improvements in living conditions. But this has not resulted in a homogeneous increase in cognitive abilities among these groups. Indeed, the performance differences observed since the beginning of the 20th century continue to persist, as if an increase in weight and height, caused by better nutrition, did not have a significant impact on intellectual abilities, especially in the sense of equalizing them. Some might still appeal to the "Flynn effect," a statistical phenomenon consisting of the secular increase in performance on IQ tests observed in several countries. But in the case of racially diverse countries like the United States, even if this phenomenon also occurred, it occurred primarily in the population as a whole, because when groups are compared, the differences tend to remain the same, for example, between ethnic and racial groups. It is still unknown what the "Flynn effect" actually consists of—whether it reflects real gains in cognitive abilities or whether it reflects changes in the tests themselves, resulting in an increase in averages. One example of this phenomenon is the increase in the average IQ or test performance of the American population, in which the first scores, when adjusted for current scores, would be about 20 to 30 points lower. If the average was 100 100 years ago, today it would be 70. But a spectacular increase of 20 to 30 points should be reflected in all social aspects, and that is not what we perceive (a statement by the scientist responsible for discovering this phenomenon). Furthermore, it is unlikely that the American population at the beginning of the 20th century had an average intelligence level at the level of intellectual disability.

Despite this very likely evidence in favor of hereditarianism, it still doesn't mean that poor environmental conditions can't impact cognitive performance or brain development in the medium and long term. The most likely conclusion is that, when they are eliminated, the increase in cognitive performance occurs according to the genetic or biological potential of the individual or population, which is not the same for everyone. This may explain the secular increase in intelligence, at least on cognitive tests, in the American population as a whole, yet another reflection of the impact of these improvements among the poorest, while also perpetuating performance differences between groups.