WHAT IS THE POLYGENIC THEORY? - CULTURE VOCABULARY - 2025

The polygenic theory or polygenism defends that the human species is divided into races whose origin is due to different lineages. It has been developed to explain the origin and evolution of man.

According to polygenism, hominids living in Africa emerged in a first wave and, years later, evolved men emerged in a second wave from Africa and met the inhabitants of those lands.

It is a theory that conflicts with the notion of original sin defended by the Catholic Church. It has also been said that it is a conception of man that served to justify slavery.

Theorists in favor of polygenism

Ernst Haeckel, who widely disseminated his interpretation of Darwin's ideas among German-speaking Germans, was a supporter of polygenism, arguing that the human being was a genus divided into nine separate species since the appearance of speech.

While Carleton Coon, defender of a modern polygenism, that each human race evolved separately (multiregional hypothesis).

In any case, it is a belief that has not been sufficiently consolidated to generate consensus among the scientific community.

Polygenism and human biology

The first theories that spread about the origin of the modern human being, proposed that the races referred to different biological species with little or no genetic flow between them.

For example, the multiregional model, based on the fossil record, suggests that a parallel evolution from Homo erectus to Homo sapiens occurred after the migration of Homo erectus from Africa (more than 800,000 years ago).

According to the model of recent African origin (RAO), all non-African populations share an ancestor: Homo sapiens, which evolved in Africa approximately 200 thousand years ago, and replaced the populations that it found outside of Africa (the Neanderthals, for example).

Indeed, phenotype, mitochondrial DNA (mtDNA) and Y chromosome investigations reveal that this migration originated from East Africa.

Being that human beings, as a species, share an ancestor and are genetically similar, what scientific basis supports the notion of races? The answer seems to lie in the field of demography.

It happens that man does not mate at random; the chances of mating are greater between beings that live in the same geographic region and share the language.

This is so both because of the natural process of genetic drift and because of the tendency of human beings to mate with those with whom they share certain phenotypic characteristics.

There are population structure studies that investigate genetic variance between populations and are based on the Sewall Wright FST. This is a statistic whose results range from zero (no differentiation) to one (no shared genetic variation).

When the results reflect a low FST value it could mean that there are recent common ancestors or high levels of migration.

Many studies reveal higher levels of genetic variation in African populations than in non-African populations; populations outside of Africa have only a fraction of the genetic diversity within it.

It must be considered that there are demographic factors that affect the genome: the size and structure of the population, the founder effect and the addition.

The non-random association of alleles is called linkage disequilibrium (LD), and science has found that Africans have lower LD than Eurasians and Americans.

That could explain why ancestral African populations maintained a larger effective population size (Ne) and consequently had more time for recombination and mutation to reduce their LD.

Beyond this and the variations imposed by the adaptation of individuals to their close environment (for example, immunity to certain diseases or the variation of melanin that affects skin color), the correlation between what is popularly understood as "race", and the actual physical variations in the human species, is practically nil.

Polygenism and religion

Given the monogenism raised by Christian Genesis (origin of humanity in a single couple), polygenism proposes that human life was formed in several places relatively simultaneously and that the name Adam does not refer to a single person but rather alludes to the collective “men” and / or “humanity”.

This interpretation, heretical until the middle of the 19th century, has been considered as an attempt to scientifically explain, without renouncing the Christian faith, the few human generations between Adam and Eve and the humans of today.

This doubt raised by Voltaire in 1756, found some followers and the resistant opposition in the Catholic Church not only for attempting against one of its main dogmas of faith, but for finding historical evidence of a biological and cultural evolution so fluid that it cannot be restricted to some stages linked by transitions.

Polygenism and human rights

Since polygenism also functioned as a scientific way to justify slavery, human rights defenders have spared no effort to refute it.

In the mid-20th century, the international movement in defense of human rights focused on biological experiments focused on investigating racial types and the hierarchies that they implied.

At that time, the discussions that were generated in the scientific community suggested a dissolution of the hierarchy between the races, even when the existence of the same was still assumed.

In fact, today molecular biology and genetics continue to try to find evidence of the existence of races. The notion of races is still valid and entrenched as a social category in the West, perhaps because of the habit, for many reductionist, of thinking in categories.

While medicine says that this type of classification allows the development of more appropriate public health policies, for other sciences it contributes to efforts to know the evolutionary history of our species, but for a human rights activist it generates stigmatization for certain populations.

References

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4. Martinez Martinez, Stefa (s / f). Polygenist theory of Paul Rivet. Recovered from: es.scribd.com.
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