The question of group-level human variation has been a hot one. Some research argues for continental, race-like groupings in which there is more variation between groups than within them (Jorde, et al., 2000) and that self-identified race is a reliable predictor for one’s genetic heritage Tang, et al,, 2005). Other research suggests while there is group-level genetic variation, it exists within a gradation of populations and not a small number of historically isolate draces (Serre & Paabo, 2004). While it is increasingly recognized that early scientific research, such as Lewtonin 1970, which denied any meaningful group-level variation was overly simplistic (Edwards, 2003). Though studies which look at only a few phenotypes continue to find little intergroup variation (Relethford, 2002), broad studies find definite intergroup variation (Rosenberg, 2005) and intragroup similarity (Rosenberg, et al., 2006) Several portions of Bjorklund & Pellegrini’s (2002) third chapter, History and Controversy, also hint at ways that human groups could be more different from each other than once thought.
One way that biological group level variation can increase is if experience can somehow be paseed from parent to child. For instance, even if two populations are genetically very similar, if they face different environments, and the effects of the environment can be passed down, you could have biologically-based differences in only one generation. This was once considered anathema to modern biology: Bjorklund & Pellegrini write that â€œInheritance, and thus genetic variation, is found only within the germ line and is not influenced by experienceâ€ (47). However, i tis now recognized that â€œphysicalâ€ and â€œbehavioralâ€ changes can be passed on (53). An early example of this was Jean Piaget’s experiment with epigenetic snails (54). In contemporary jargon, we should say that â€œfemales pass on cytoplasm (i.e., the cell body) to their offspring [and so environmental] changes that induce chemical changes in the cytoplasm can thus be inherited through the motehr but not through the fatherâ€ (56). On the same page, the authors note that while this cytoplasm is not itself genetic, â€œCytoplasmic inheritance should not be thought of as nongenetic [because] it necessarily expressed its effect on the genes.â€
It’s relatively easy to imagine how this could work. Imagine two otherwise similar populations which are divided from each other. This division forces both to become relatively self-contained breeding populations and leads to differences in diet, with one population eating nutritious food and the other near starvation. After just a few generations, cytoplasmic variants adept to surviving and reproducing in starvation-conditions could become very widespread in the one population, while an opposite set of cytoplasmic variants become widespread in the other population. Frighteningly, this may be happening in Korea. The height difference between North and South Koreans is already four inches (Ser & Team, 2006). If some of this difference is epigenetically, cytoplasmically inherited, this could create a de-facto â€œracialâ€ divide among Koreans that might last centuries, even after a return to environmental equality.
Non-coding DNA is another thing that may have led to a discounting of human intergroup genetic diversity. Bjorklund & Pellegrini describe this DNA as â€œdormantâ€ and â€œunderusedâ€ (57). However, the 97% of our genome that is intergenetic â€œcan have dramatic effects on the way that nearby genes are activated to make proteinsâ€ (Pinker, 2002, 78). One such piece of junk DNA, Dopamine Receptor D4 7 Repeat â€“ has been tied to ADD and novely seeking (Laucht, Becker, & Schmidt, 2006). As earlier studies of human differences focused on coding DNA, such as protein loci and blood group loci (Latter, 1980), these studies have essentially just ignored 97% of human genetic difference. This is especially sad as junk DNA can be inserted into RNA, thus becoming functional (Lev-Maor, Sorek, Shomron, & Ast, 2003).
Yet the idea of intergroup genetic diversity among homo sapiens causes controversy. Indeed, the idea that genes matter in the human species causes controversy Richard Lewtonin, whose work denying the existence of races was cited earlier, famous accused E.O. Wilson of mirroring “the ideologies of the bourgeois revolutions of the eighteenth centuryâ€ (Ridley, 2003, 243). How much more disturbing it might be if not only do children already know about â€œlanguage… objects… and social relationsâ€ (Bjoklund & Pellegrini, 2002, 61), but that groups of children vary in their knowledge of these objects. For instance, if one group has a higher general intelligence ability while another group as a higher rythmatic intelligence (Lynn, 2006). Does this imply that one genetic grouping is more valuable than another?
The answer, of course, is no. As Steven Pinker (2002, 145) wrote â€œThe case against bigotry is not a factual claim that humans are biologically indistinguishable. It is a moral stance…â€ We are all equally human. We are all equally valuable. No evidence, ever, could change that.
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Evolutionary Cognitivism, a tdaxp series
1. Selection and Cognition
2. Epigentics and Diversity
3. Children and Civilization
4. The Implicit and the Explicit
5. Man Among Men
6. More Than Genes