Lewontin's paradox: what it is and what it says about the concept of human races

Evolution is the process by which organisms change over time. Spontaneous heritable mutations produce variability in the populations of living beings, which allows natural selection to "favour" and select those individuals best suited to the around.

Along with genetic drift and gene flow, natural selection explains much of the process. evolutionary: the strongest remain, while the weakest do not reproduce and their genes are lost throughout the history.

Thus, we can affirm that evolution bases its operation on genetic inheritance. If a character is not heritable, its variability in the population matters little, since it will not condition the phenotype of the following generations. All of these bases seem obvious today, but they have been challenged by different thinkers over the years, in order to get to the point where we are today.

Today we introduce you to the world of population genetics and unresolved issues, at least from a genetic and social point of view. Do not miss the fascinating Lewontin paradox and how it applies to human existence.

• Related article: "The theory of biological evolution: what it is and what it explains"

the foundations of evolution

Before introducing the Lewontin paradox, it is necessary to establish certain bases. Human beings present 23 pairs of chromosomes in each of our cells, that is, a total of 46.. These contain genes, which in turn differ in alleles, which are defined as each of the alternative forms in which the same gene can be expressed. Thus, any gene will be made up of 2 alleles, A1 and A2, for example.

Of the 46 chromosomes found in the nucleus of our cells, one comes from the mother and one from the father. Thus, if a mother has alleles (aa) for a gene and a father has alleles (AA), the only possible frequency in the offspring would be: Aa, one allele from the father (A) and one from the mother (a). ). The dominant alleles (A) are those that only need one copy in the gene to manifest themselves, while the recessive ones (a) have to present two copies in the genome to become valid (aa). The fixed position of this gene or any other on a chromosome is known as a locus.

When the two alleles are the same for the same trait, whether dominant (AA) or recessive (aa), the individual is said to be homozygous for a gene. When this is not the case, the individual is called heterozygous (Aa), despite the fact that only the dominant allele (A) is externally manifested over the recessive one (a).

With this express class, we understand a little about the mechanisms of evolution: from a theoretical point of view, the more individuals present genomes with heterozygous characters, the more likely it is that the population will maintain itself over time, since natural selection will act negatively on some characters, but may select others positively.

In general, loss of genetic information results in homozygosity, leading a species to extinction in the long term. Processes like the Genetic drift or inbreeding favor this situation, but they are beyond our competence at this time. With these bases established, we can dive into the Lewontin paradox.

What is Lewontin's paradox?

Richard Lewontin is an evolutionary biologist, geneticist, and philosopher who was born in New York, United States, in March 1921. He is still alive, at an impressive 91 years of age. This fascinating researcher was one of the pioneers in applying molecular biology techniques, such as gel electrophoresis, which are still essential in the field of science to this day. He specialized in population genetics, as we will see in the following lines.

Lewontin was a proponent of the hierarchical theory of evolution.. Although it is difficult to find information about this current of thought, it can be summarized in the following lines: in it, natural selection does not act solely on based on genes (as we have seen so far), but also cells, organisms, species and clades, among others, are considered evolutionary units. organizations.

Transporting this postulation in the world of animal populations, Lewontin's paradox would come to tell us that theoretical predictions about the relationship between population size and genetic diversity do not hold up in the real world. As anecdotal as this may seem, you will see how the human collective is transported.

• You may be interested in: "Richard Lewontin: biography of this biologist"

How does Lewontin's paradox apply to humans?

The Lewontin paradox (or "Lewontin's fallacy", for its translation into English) has led to a great debate in the scientific community, since based on it it is argued that the conception of the human race has no sense. In an article published in 1972, Richard Lewontin postulated that 85% of genetic variation in humans occurs between individuals of the same population and that, failing that, only the remaining 15% is due to differences between ethnic groups.

This means that, broadly speaking, one individual is different from another because of their individual condition and not because of their ethnic origin or supposed racial heritage. Thus, the theories that circulate around the race would be dismantled, and the supposed differences behaviors between individuals could only be explained by cultural constructs, not by genetics. If the breed does not explain variations at the genotypic (genes) or phenotypic (external characteristics) level, its usefulness in the field of taxonomy is nil.

Here some of the concepts that we have explained to you previously come into play. Certain researchers (such as Anthony William Fairbank Edwards) have tried to dismantle the Lewontin paradox, since they do not consider the researcher's approach to be correct. While it is true that the frequency of different alleles (AA or aa, for example) at an individual locus does not report significant difference between ethnic groups, it does when taking into account several areas of the genome at the same time. time. We explain ourselves.

If allele frequencies are factored at several loci (plural of locus) at the same time, this research statistician argues that individuals can be classified into an ethnic group with almost 100% reliability. That is, the allele frequencies tend to "cluster" across ethnic groups, so if they are only taken into account account the alleles separately, clearly the population reality of the being is not being represented in its entirety human.

Between props and fallacies

Some renowned biologists, such as Richard Dawkins, agree with Lewontin that individual variability is far more important than ethnic variability. when explaining genotypic and phenotypic differences in humans. Despite this, he does not think that the concept of race or ethnicity has no taxonomic interest: "no matter how small, if a racial characteristic is linked to another racial characteristic, it is already informative and, therefore, of importance taxonomic”.

The question that remains in the air, despite the musings, is the following: is "more" different genetically a person of one race in comparison with that of another race, or two individuals different from the race same race?

Summary and considerations

According to different biologists around the world, and based on articles published relatively recently, "the use of the concept race biology in human genetic research, so contested and confused, is problematic at best and harmful at best. worst". Undoubtedly, the Lewontin paradox and its ensuing debates are of great biological interest, but we must not forget that we are talking about human beings with diverse feelings and identities, not statistics and gene expressions.

To this day, the concept of the human race is considered problematic and offensive and, therefore, it is not there must be a scientific basis to support its replacement by other more correct words, as ethnicity. Science is a product of society, and not vice versa, so it must adjust to the new social codes in the most inclusive and permissive way possible. As much as something is "scientifically correct", if it hurts the collective sensitivity and closes bridges of dialogue, it does little to encourage the search for knowledge.

Bibliographic references:

• Depew, D. J. (2018). Richard Lewontin and the Argument from Ethos. Poroi: An Interdisciplinary Journal of Rhetorical Analysis & Invention, 13(2).
• Edwards, A. W. (2003). Human genetic diversity: Lewontin's fallacy. BioEssays, 25(8), 798-801.
• Kaplan, J. m. (2011). 'Race': What biology can tell us about a social construct. eLS.
• Lewontin, R. c. (2005). The fallacy of racial medicine: confusions about human races. Genewatch: a bulletin of the Committee for Responsible Genetics, 18(4), 5-7.
• Moore, D. S., & Shenk, D. (2017). The heritability fallacy. Wiley Interdisciplinary Reviews: Cognitive Science, 8(1-2), e1400.
• Okazaki, A., Yamazaki, S., Inoue, I., & Ott, J. (2020). Population genetics: past, present, and future. Human Genetics, 1-10.
• Sober, E. (2020). AWF Edwards on Phylogenetic Inference, Fisher's Theorem, and Race. The Quarterly Review of Biology, 95(2), 125-129.