Is the Iceland experiment an example of the social environment being more important than biology?

An analysis of the intergenerational shift in behaviors in that country

In the 1990s, over 40% of Icelandic youths aged 15 to 16 reported excessive alcohol consumption. Other substances—such as cigarettes and marijuana—were also consumed at levels comparatively higher than in other European countries. However, following a series of measures adopted by the Icelandic government, this "hedonistic" youth culture changed dramatically; today, only 5% of young people in the same age group report heavy alcohol consumption, compared to 42% three decades ago. Regarding cigarettes and marijuana, the intergenerational differences in consumption are equally striking: dropping from 23% to 3% and from 17% to 7%, respectively.

https://www.espn.com.br/futebol/artigo/_/id/4306536/lado-b-da-copa-islandia-o-pais-que-usou-o-esporte-para-combater-o-alcoolismo-entre-jovens

If this remarkable behavioral shift is directly linked to the introduction of government measures aimed at fostering healthy habits—such as sports—from an early age, as well as restricting access to alcohol and other drugs, then it serves as a prime example of human plasticity. It illustrates the broader capacity to alter or change behavior—if not about a single individual, then at least within a group (it would be interesting to know the current status of the Icelandic youths who were assessed in the 1990s and reported high consumption of alcohol and other substances). It also demonstrates just how powerful an influence the environment can have on us. ...of just how socially conformist we can be... But it also shows that, even before—when "Icelandic youth" were disproportionately mired in habits harmful to physical and mental health—the situation didn't apply to the entire group; 60% (a majority) did not fall into the "bad habits" statistics... It demonstrates that even when homogenizing forces exist within certain social groups, there is a strong likelihood that at least a minority will not "follow the herd"... This also highlights the power of biology itself as an influence on behavior—perhaps the most important factor. After all, both the young person who falls into the world of addiction and the one who does not are primarily—and, I would argue, deterministically—influenced by their behavioral biology: the morphological characteristics of their brains and the hormonal makeup of their bodies, in constant interaction with the environment, these traits manifest as behavioral tendencies that may be similar or vastly different. There is no such thing as someone "from nowhere" taking up smoking while another person in the same group quits; in terms of behavior, nothing ever happens "from nowhere." There is no *blank slate* inside our heads leading us down completely random paths; the range of behaviors we can adopt is predetermined—provided we aren't born literally without brains, and given that the brains we are born are result from combinations of our parents' genetic material, which already possesses its own specific individual makeup. We are certainly born with developing brains, but never without pre-existing or predetermined elements—contrary to the notion of a blank slate waiting for experience to write upon it. Although many believe this—including supposed experts in related fields—the Icelandic experiment does not prove that human genetics or biology is entirely a product of the social and cultural environment; rather, it shows that because our biology is intrinsically plastic, it allows for a wider range of behavioral variation. Some might still argue that various individual and environmental factors operate as a chain of influences... ...can lead some or many to follow certain paths. The "anatomical structure" of multiple, highly specific causal factors leading an individual or group to adopt certain behaviors is not inherently superfluous, as it can serve to illustrate a trajectory. However, it does not support the argument—which might otherwise be used to bolster the "blank slate" hypothesis—given that intrinsic predispositions remain the most important factor. Indeed, there is a correlation between addiction and certain personality traits, such as neuroticism, as well as physiological predispositions—for instance, the capacity to tolerate high levels of alcohol in the bloodstream and how this can contribute to the establishment of a specific cycle of alcohol addiction. 

Furthermore, there is another interesting fact not shown in the linked report: the crime rate in that country has not decreased significantly since the government began steering younger generations away from cigarettes, marijuana, and alcohol, as illustrated in the linked graph..below, having remained relatively constant (generally very low) from that time until the most recent years of the 2020s. This is interesting because it is common to attribute some irrationally antisocial behaviors to alcohol or drug abuse. And even though there is a logical link between behavioral changes and excessive substance use, even in that dire scenario of total surrender to addiction, intrinsic factors—such as predominant personality traits—continue to exert influence; after all, not every addict goes around mugging people or committing even graver acts, such as unprovoked violence or even homicide. This may demonstrate that certain behaviors or habits are more malleable than others, but it also suggests that this experiment is particularly well-suited to countries with populations ethnically similar to Iceland’s—such as its Scandinavian cousins—whereas populations that are culturally, psychologically, and cognitively distinct might well show different responses... Even if it could be adopted as a medium- to long-term public policy in other countries...

https://www.macrotrends.net/global-metrics/countries/isl/iceland/crime-rate-statistics

To answer the question posed in the title: the social environment certainly influences human behavior. However, behavior is never shaped solely by the environment; for the interaction to be complete, it depends first on the behavioral biology of the population or the individual. Secondly, if the "environment" is merely a set of factors determined in arbitrary and variable ways, the only true agent—and the primary one in this dynamic—is always the living being/ human being. Consequently, the most important directives and determinants originate from within that individual. Just as a human being cannot fly unaided without the necessary biological machinery and physical and mental capabilities, neither can they overcome their own limitations—specifically, the very traits that define and characterize them. For if—based on the example in the text—he lacks the psychological and even physiological predispositions to become addicted to alcohol or drugs, it is highly likely that he will not end up trapped in that problematic cycle of reward in his daily life, even if he happens to be exposed to it...

A Pseudo-Paradoxical Validation of Biological Determinism

Epigenetics Does Not Prove the Tabula Rasa/Blank Slate Ideology...

During a few months of the harsh European winter of 1944-45, Nazi invaders cut off all food supplies to 4.5 million people in the still-occupied regions of the Netherlands, resulting in a mass famine that killed approximately 20,000 people from severe malnutrition. Decades later, its consequences continued to be felt in the children of women who were pregnant during that critical period in the history of the Netherlands, as they were found to have a higher incidence of metabolic diseases, such as diabetes and obesity, cardiovascular problems, and schizophrenia, than the rest of the population of the same country.

It seems obvious that extreme conditions, depending on what is considered extreme for each species, often cause extreme effects on the organisms of living beings. However, it is also necessary that these organisms are not adapted to withstand such conditions, as is the case with humans. Therefore, it is not only the environment that influences them, because they respond and interact according to their own natures (their adaptive limits and potential).

Regarding the famous example above, often used to demonstrate transgenerational epigenetic effects, it does not prove that the environment is more important than biology, even though many have reached that conclusion. In fact, it proves that it is biology that determines the behavioral and/or organic reactions of living beings to the different environmental conditions in which they find themselves, always providing the final response. Therefore, if the human organism were fully adapted to a situation of food shortage, it would not suffer major repercussions if subjected to the same.

After all, what makes some species more adapted to extreme conditions, such as some bacteria, and others not?

Mainly their biology.

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.

A hypothesis based on the correlations found between month or season of birth and psychological tendencies

 There are some interesting studies that have found positive, though relatively modest, correlations between the month or season of birth and certain psychological tendencies: those born in the winter, especially late winter and early spring, at least in the Northern Hemisphere, are at greater risk of developing mental disorders, especially schizophrenia. The most common explanation is that pregnant women who conceive during this period are more exposed to viral infections, and that, if infected, their children could experience long-term effects later in life, including mental disorders. Another possible factor is that cold weather induces a vitamin D deficiency, which could complicate the normal development of pregnancies. A correlation between prematurity (or low birth weight) and schizophrenia (and psychopathology in general) has also been noted. Perhaps normal brain development that is abruptly interrupted by external factors could also be a long-term trigger for the expression of a mental disorder. Or it may be that genetic, and therefore hereditary, factors explain a good portion of psychiatric disorders. First, a couple whose two partners have the same disorder are at greater risk of passing it on to their natural descendants than a couple with only one carrier, and especially if there is no explicit sign of mental disorder between a pair of humans biologically capable of procreating or who have already done so. It is precisely this last possibility that seems most likely to me, perhaps because it is the least extraordinary. First, because assortative relationships, in which there is a mutual and active interest in mating based on the perception of phenotypic similarities—usually a combination of biotype, personality, and social circumstances—increase the likelihood that individuals of opposite sexes with the same health risks, including psychiatric ones, will enter into a relationship that will result in natural offspring. Second, the proposed mechanism to explain the correlation between being born in winter (cold, in the Northern Hemisphere) and developing certain mental disorders requires empirical proof, and to my knowledge, I don't know if it exists in humans. Third, most individuals born in winter do not become schizophrenic, although it would be interesting to see if a higher proportion of individuals born in this period (especially in temperate climates) develop other psychiatric disorders, or at least a greater expression of associated personality and cognitive traits. Fourth, human individuals with different personality profiles (which are predominantly stable patterns of behavior) tend to exhibit different habits, likely also in mating. Even more directly related to this correlation between month or season of birth and psychological tendencies, one of the behavioral or personality differences that may explain it is climate preference. Those who prefer cold weather (or who don't exhibit this type of preference) feel more motivated during this time of year, even to have sex/procreate (or who don't exhibit any differences in motivation throughout the year), while the opposite pattern occurs for those who prefer warm weather. For example, more emotionally unstable individuals tend to feel more "depressed" or less motivated in cold weather, especially in environments with harsh winters, including for sexual intercourse. The opposite pattern occurs during the warmer months. And since human pregnancy lasts, on average, nine months, a pregnancy that began in summer or spring will complete its cycle in fall or winter. So perhaps the most important element in this situation is the influence of personality type, which expresses various biological aspects: hormonal, mental, genetic... and not necessarily the influence of the environment acting directly on the human organism, even if it influences it indirectly, through behavior.

Okay, but then how can we explain this pattern in tropical and equatorial climates, if these climates are characterized by less significant temperature variations?

Even if there is less temperature variation in these regions, the underlying factor is the same: there are differences in mental traits among human beings that result in differences in habits. In addition, these mental traits are not just abstractions, as they also express more organic and variably hereditary aspects of the body. So, even if this pattern isn't confirmed in all regions, its possible absence of correlative universality does not invalidate its evidence of specific correlation. But perhaps this correlation is nothing more than "genetic confounding," in which a correlation that suggests environmental causality for a given behavioral tendency actually has as its underlying, primary, and most influential factors: biological characteristics, such as personality traits, which are also transmitted from parents to children. And, before concluding this text, I wonder if the risk of premature birth (or even miscarriage) could also be an intrinsic and variably heritable predisposition, not just a completely random incident—that is, one that doesn't present the same probability of occurring in any pregnant woman. I know there are studies showing differences in this risk between ethnic or racial groups (during a quick search on this topic, I found studies showing that, in fact, there is indirect evidence of a genetic influence on this risk)...

Sources:

Season of birth in schizophrenia: a maternal-fetal chronobiological hypothesis

https://pubmed.ncbi.nlm.nih.gov/21382670/;

https://www.uol.com.br/vivabem/noticias/redacao/2017/10/06/maioria-dos-casos-de-esquizofrenia-e-genetico.htm

Heritability of Schizophrenia and Schizophrenia Spectrum Based on the Nationwide Danish Twin Register

https://www.biologicalpsychiatryjournal.com/article/S0006-3223(17)31905-4/abstract;

Family history is a predictor of current preterm birth

https://www.ajogmfm.org/article/S2589-9333(20)30270-6/pdf;

The Role of Genetics in Preterm Birth

https://link.springer.com/article/10.1007/s43032-023-01287-9;

Levels of the stress hormone cortisol are higher in women who give birth in the autumn and winter than those who give birth in the spring or summer, finds a new study by researchers at Cardiff University.

https://www.cardiff.ac.uk/news/view/1547555-new-research-could-explain-why-babies-born-during-winter-are-at-higher-risk-of-developing-mental-health-disorders

An example that explains more precisely the hierarchy of influences on human behavior

 Why does crime tend to be lower in small towns?

The bigger the city, the greater the tendency for high crime rates. And the same pattern coincides, only in the opposite direction, for small towns. Even in more violent countries, such as Brazil.

So, what are the factors behind this phenomenon?

Many will point to the environment as the main factor. They will say that, in big cities, there are more people, and this factor alone increases the risk of human conflicts that result in violent acts. They will also say that social inequalities are greater and this leads some or many people, especially the poorest, to envy those who have more money than them, increasing the risk of engaging in criminal activities. And that these first two factors also fuel the urge for competition, especially among men, increasing the risk of them becoming involved in criminal activities or violent acts. They could also cite other, more specific environmental factors, such as greater access to psychotropic drugs, to claim that what is generally lacking in small cities and exceeds in large ones is sufficient to explain why there is this predominant trend of statistical differences in crime. And what's more, because they are not wrong, if, in fact, it is entirely feasible that these environmental factors have an influence on human behavior. However, these same people enter a state of absolute denial when they conclude that only the environment explains how we behave, because, even though there is a certain logic in not concluding in advance about biological or genetic factors, if they have not yet been fully identified and understood by science, it is a rationally pragmatic matter to deduce, confidently, that these factors are as influential or more influential and that discarding them, as these "circumstantialists" do, is, at the very least, imprudent. Although we do not yet have a complete picture of direct evidence on the genetic or biological influence on human behavior, it is already possible to perceive an accumulation of indirect evidence, through the observation of patterns, which confirm it, for example, by the perception of stability and predictability, in the medium and long term, of personality traits and intelligence. So, if it is true that densely populated urban environments present an increased risk of violent behavior, it is also true that individuals with different behavioral dispositions are impacted in different ways in the same environments or when they are exposed to the same stimuli and pressures, if not the majority of human beings in these spaces become violent or prone to committing crimes, not even in the outskirts of large cities. Therefore, it is not only the environment that influences human behavior, but also our own mental characteristics, which are more innate or intrinsic, and not just reflections of the influence of the environment on us. Again, it is a deduction that can be made, precisely because they are more stable and predictable in the medium and long term, because they are, on average, less influenced by social interventions or because they express themselves in a relatively independent way to pressures and stimuli (our behaviors are not absolutely logical, in the sense of reciprocal, to what happens around us or that interacts with us), there being, most likely, a coincidence or confluence between mental traits and environmental interaction factors, when there is a reciprocal response, and not that "factor x caused a behavioral expression to emerge, out of nowhere, in a certain individual". In conclusion, the most appropriate explanation for this social phenomenon, which is also behavioral, psychological, cognitive, genetic..., is that individuals with significantly higher levels of willingness to engage in violent, selfish or impulsive behavior feel more stimulated to practice them in densely populated urban environments than in less populated environments, also due to all the factors mentioned above, which serve as triggers or catalysts for tendencies and not as primary sources from which they originate. Because if only the environment had a preponderant role of influence, there would always be a great uniformity of behavior in response to it: a certain environment, pressure or stimulus, probably because of the variation in the disposition of mental characteristics (more intrinsic).

Final additional questions

Are these differences in criminality also a question of selective migration? Of mutation? And of statistical proportion??

1-

Do small towns attract or retain more individuals with a more docile temperament, while big cities tend to attract more impulsive, greedy and selfish types?

This is a very important question, because it makes sense that different environments/tend to attract or retain different types of human beings. Not that this factor fully explains this statistical difference in crime, but it can serve as an addendum that can partially explain this social phenomenon.

2-

Larger populations are more likely to have higher values ​​of genetic diversity, because they are more susceptible to mutations that occur more naturally among them than in small populations, including mutations related to mental disorders, personality disorders...

3-

5% of psychopaths in a city of 15 thousand inhabitants (750) is not the same as 5% of psychopaths in a city of 2 million (100 thousand), right??

Therefore, having a large population increases the absolute proportion of individuals with mental disorders of a moral nature, such as psychopathy, and therefore increases the probability that they will engage in violent or criminal acts. This, without taking into account possible statistical differences in the incidence of psychopathy between small and large cities (the selective migration factor).

Uma das palavras mágicas, favoritas da religião esquerdista: "diversidade"

 "Estudo mais completo sobre o genoma dos brasileiros revela que temos a maior DIVERSIDADE genética do mundo"

Mas isso não tem se refletido em 

Pessoas, em média, mais "bonitas"

Mais inteligentes 

Educadas/respeitosas 

Empáticas???

???

Claro, culpemos apenas o meio: a colonização, a falta de educação de qualidade, o homem branco mau...

Supostamente, foram encontradas vantagens genéticas no "nosso povo", por causa da miscigenação, relacionadas com saúde e fertilidade. 

Ok...

Mas, a expectativa de vida do brasileiro não parece ser das maiores, né??

E quanto à saúde: obesidade, transtornos mentais e outros tipos de doenças, parecem ser tão ou mais comuns aqui do que em países mais geneticamente homogêneos, como o Japão e a Finlândia...

Enfim, a diversidade, de fato, é mais como uma palavra mágica que significa "quem sabe?" (churin churin flun flains...). Pode ser boa ou ruim. E no caso do contexto brasileiro, sinceramente...

Sobre hereditariedade, carga mutacional e recombinação fenotípica/About heredity, mutational load and phenotypic recombination

 Eu já comentei sobre isso nesse texto: "Sobre hereditariedade, variação e a metáfora da massinha". Então, além de sempre herdarmos, variavelmente falando, recombinações dos materiais genéticos dos nossos pais biológicos, as mesmas também podem resultar em grande variação entre os descendentes, mesmos dos mesmos progenitores, especialmente se, junto a esses materiais, existir uma maior carga mutacional. Então, quando há mais mutações, discretas ou não, durante a transmissão hereditária e que resulta em recombinação, essas podem gerar fenótipos muito diferentes entre si e até mesmo únicos ou raros. E me refiro em especial aos que estão relacionados com características de personalidade e inteligência. E como eu disse no outro texto, essa variação pode explicar boa parte das diferenças psicológicas e cognitivas, sem que se apele para o meio como fator proeminente em potencial. 

I have already commented on this in this text: "On heredity, variation and the clay metaphor". So, in addition to always inheriting, variably speaking, recombinations of genetic materials from our biological parents, they can also result in great variation between descendants, even from the same parents, especially if, together with these materials, there is a greater mutational load. So, when there are more mutations, discrete or not, during hereditary transmission and resulting in recombination, these can generate phenotypes that are very different from each other and even unique or rare. And I am referring in particular to those related to personality characteristics and intelligence. And as I said in the other text, this variation can explain a good part of the psychological and cognitive differences, without appealing to the environment as a potential prominent factor.

3 pontos para explicar similaridades geracionais e diferenças intergeracionais de comportamento /3 points to explain generational similarities and intergenerational differences in behavior

 1. Gerações tendem a expressar aspectos estruturais ou socioeconômicos de suas épocas

Então, se os jovens, atualmente, estão em maior risco de ficarem desempregados do que nos tempos de juventude das gerações mais velhas, não é apenas porque tem mais preguiçosos entre os jovens atuais, mas também ou especialmente por causa de uma maior estagnação econômica (entre outros fatores, tal como o aumento da automação), resultando em um déficit entre a oferta e a demanda de emprego...

Mesmo diferenças físicas, como de estatura e peso entre as gerações, também podem ser reflexos (nesse caso, cumulativos) de mudanças nas estruturas socioeconômicas, de quando tinha mais pobreza e desnutrição até quando passou a ter mais fartura.

2. Gerações expressam aspectos genéticos e fenotípicos correntes de suas populações 

Diferenças nos padrões seletivos e reprodutivos podem gerar mudanças na paisagem genética entre as gerações e mais notadamente entre as gerações mais distantes. Por exemplo, décadas com baixas taxas de fecundidade, grande aumento da natalidade tardia e da reprodução assortativa* (com base em similaridades fenotípicas do casal) podem causar um acúmulo progressivo de mutações de uma geração para a outra.

* Parcial e possivelmente associada a uma maior incidência de casos de autismo, por exemplo, no vale do Silício, região do estado da Califórnia, nos EUA, com grande concentração de engenheiros, cientistas e técnicos da computação mais propensos a estarem "dentro do espectro"

E como citado acima como parte reflexiva do estado dominante das estruturas socioeconômicas de uma geração, diferenças físicas também expressam o estado corrente de características fenotípicas da mesma, tal como a estatura e o peso. 

3. Gerações tendem a expressar aspectos culturais e psicológicos específicos às suas primeiras décadas de existência

A partir de suas tendências reativas mais comuns a esses aspectos, tal como por diferenças culturais de criação, por exemplo, das gerações mais antigas, em que o modelo era mais "tradicional" ou autoritário, e das gerações mais novas (atualmente, nesse início de século XXI), em que tem havido uma maior atenuação desse autoritarismo dos pais em relação aos seus filhos. 

Além disso, o que é universal à toda geração é uma ligação emotiva à cultura dominante de sua época, especialmente de seus "anos formativos', de infância e juventude, ainda que a força dessa ligação também dependa de outros fatores, tal como a compatibilidade de características intrínsecas, como a personalidade, com a cultura ou, subculturas de influência, no caso das tribos urbanas.  

1. Generations tend to express structural or socioeconomic aspects of their times

So, if young people today are at greater risk of becoming unemployed than in the youth in older times, it is not only because there are more lazy people among today's young people, but also or especially because of greater economic stagnation ( among other factors, such as increased automation), resulting in a deficit between job supply and demand...

Even physical differences, such as height and weight between generations, can also be reflections (in this case, cumulative) of changes in socioeconomic structures, from when there was more poverty and malnutrition to when there was more affluence.

2. Generations express current genetic and phenotypic aspects of their populations

Differences in selective and reproductive patterns can generate changes in the genetic landscape between generations and more notably between more distant generations. For example, decades with low fertility rates, a large increase in late births and assortative reproduction* (based on the couple's phenotypic similarities) can cause a progressive accumulation of mutations from one generation to the next.

* Partially and possibly associated with a higher incidence of autism cases, for example, in the Silicon Valley region of the state of California, in the USA, with a large concentration of engineers, scientists and computer technicians more likely to be "within the spectrum "

And as mentioned above as a reflective part of the dominant state of the socioeconomic structures of a generation, physical differences also express the current state of its phenotypic characteristics, such as height and weight.

3. Generations tend to express cultural and psychological aspects specific to their first decades of existence

Based on their more common reactive tendencies towards these aspects, such as cultural differences in upbringing, for example, of the older generations, in which the model was more "traditional" or authoritarian, and of the younger generations (currently, at the beginning 21st century), in which there has been a greater attenuation of this authoritarianism of parents towards their children.

Furthermore, what is universal to every generation is an emotional connection to the dominant culture of their time, especially their "formative years" of childhood and youth, although the strength of this connection also depends on other factors, such as compatibility of intrinsic characteristics, such as personality, with culture or, subcultures of influence, in the case of urban tribes.