Pedagogy in Action > Library > Earth History Approach > Teaching the Central Themes of Science > Evolution > Human Race

A New Perspective on Race

Consistent physical distinctions between groups of people from different areas, some of which can be readily observed (skin color, average build, etc.) and some of which can not (blood type distribution, etc.) are caused by genetic variation between those groups. Cultures divide people into races based on these physical, ultimately genetic differences.

But how important is race and how distinct are the races from one another?

  • Are there genetic differences that we can't see that are important: ones that affect people's ability to learn math, for example, or their ability to control their tempers?
  • How consistent are the differences? Are all negroids darker-skinned than all Caucasians? Can you identify a person's race from a blood sample? This question is even more important if there are genetic differences between races that are important.

Findings from Genetic Research

A lot of genetics journals archive their abstracts (sometimes with links to the entire article) at PubMed (more info) .

  • Human beings have very low genetic variability. Probably the entire species is descended from a single family that lived about 200,000 years ago.
  • Most (85%) of our genetic variation is within populations rather than among them, even when different sequences of DNA (or proteins) are examined (Barbujani et al., 1997 ). Statistical divisions of humanity based on different kinds of genetic data do not group people consistently into races (Romualdi, 2002 ).
  • Many of the genetic distinctions among races are based on commonness versus rarity of certain alleles (forms of a gene), but the same alleles are usually found in all human populations. There are very few alleles (such as the one that causes Tay-Sachs disease) or genetic markers that are found only in one race, and those tend to be fairly rare within that race.
  • Among the few genes that vary consistently between populations is the one believed to have the greatest effect on skin, hair, and eye color: MC1R (Ranaa et al., 1999 ).
  • The greatest physical and genetic diversity among humans is among the people who live in Africa today (Relethford and Harpending, 1994 ).

Findings from Fossil Remains

Physical anthropologists and archaeologists are frequently working with geneticists and publishing their findings in genetics journals.

  • The remains of modern humans Homo sapiens and the technology associated with them are found in Africa tens of thousands of years before they appear in the rest of the world (e.g. Brooks et al., 1995 ).
  • The mitochondrial DNA extracted from the bones of Neanderthal people indicate that they are not related to modern Europeans or any other living humans (Krings et al., 1997 , Ovchinnikov et al., 2000 ). Thus the modern people of Europe all immigrated from elsewhere, likely Africa or Asia.

Overall Findings

  • The genetic differences that divide races appear to be new, geologically speaking, and tend to result from harmless mutations (differences in blood type) and adaptations to recent environments (skin color).
  • Traits that people consider important, like certain forms of intelligence and self-control, are most likely going to be important in mate selection, so alleles that enhance these traits will spread to spread throughout the human gene pool in all habitats and increase in frequency to a greater degree than alleles that don't. Consequently, alleles that favor useful traits will be overwhelmingly common in all populations.
  • Mutations within populations have produced genetic differences among individuals that are greater than those among populations.
  • The idea of a recent African origin is still under investigation, as is the idea of a recent common ancestry for all living people.

Resources

Olson, 2001 . The Genetic Archaeology of Race. The Atlantic Monthly - April: a summary written for the educated public.

References

  • An apportionment of human DNA diversity. Barbujani et al., 1997 Based on multiple markers within nuclear DNA samples from individuals in different populations, the authors found 85% of the variance in their sample was between individuals within populations. (citation and description)
  • Dating and Context of Three Middle Stone Age Sites with Bone Points in the Upper Semliki Valley, Zaire. Brooks et al., 1995 Relics found at three sites in eastern Zaire are greater than 90,000 years old and are typical of those associated with anthropologically modern humans. (citation and description)
  • Neanderthal DNA Sequences and the Origin of Modern Humans. Krings et al., 1997 Neanderthal mitochondrial DNA was found to be radically different from that of modern humans. Modern Europeans are closely related to the rest of humanity and are not descended from Neanderthals. (citation and description)
  • Molecular analysis of Neanderthal DNA from the northern Caucasus.. Ovchinnikov et al., 2000 The authors sequenced mitochondrial DNA preserved within the bones of a Neanderthal. It resembled DNA from another Neanderthal, but not from any modern humans, nor from the Europeans. (citation and description)
  • High Polymorphism at the Human Melanocortin 1 Receptor Locus. Ranaa et al., 1999 MC1R regulates production of different kinds of melanin, and is a major determinant of human coloration. It seems to have been subject to selection, recently in African populations. (citation and description)
  • Craniometric variation, genetic theory, and modern human origins. Relethford and Harpending, 1994 The authors study craniometric variation in human populations in four regions, and find within-population variation to be greatest in Africa. (citation and description)
  • Patterns of Human Diversity, within and among Continents, Inferred from Biallelic DNA Polymorphisms. Romualdi, 2002 The authors continue to find that 85% of autosomal DNA variation is within a population, but Y chromosomes tend to vary more between populations. (citation and description)