This argument rests on all five of these assumptions:
- Racial differences in brain size exist
- Racial differences in brain size are entirely or mostly due to genetics
- Such differences are large enough to explain group differences in IQ
- The relationship between brain size and IQ is causal
- Between-group comparisons show a consistent relationship between brain size and IQ
The first of these assumptions may be true, as Rushton has reported in many studies (e.g. Rushton & Ankney 1996; Rushton 1992, 1994), though there is reason to believe that these studies, and others with similar conclusions, are seriously flawed (Cain & Vanderwolf 1990; Kamin & Omari 1998). Moreover, Rushton's work on this topic has been criticized for using data from museum collections of skulls. These samples are obviously not representative, given that they were often compiled in the 19th century, when the belief in a link between brain size and racial differences in personality traits was widespread (Weizmann et al. 1991, p. 46). It has also been criticized for lumping together data on skulls from disparate populations ("aggregational errors", as Cernovsky (1993) has called them) and for "adjusting" for body size without a clear reason (Winston 1996). Even if it is, though, it doesn't matter, as I explain below in discussing the four other assumptions.
The second of these assumptions may also be false. As Nisbett et al. (2012, p. 146) noted, "Brain size of full-term Black and White infants is the same at birth, and several postnatal factors known to reduce brain size are more common for Blacks than for Whites."
What about the third?
Kamin & Omari (1998, later K&O) maintain that this assumption is false, writing: "Possible relations between head size and measured IQ are so small that they cannot possibly explain black-white differences in IQ." Rushton & Ankney (2000) responded by criticizing this review for four detailed reasons, as they outline in their paper's abstract. They go into a lot of detail arguing that K&O ignored "...the relation between brain size and IQ established by magnetic resonance imaging and the race differences in brain size established by MRI, autopsies, and endocranial volume". However, they do not seem AFAICT to address the "they're too small point" K&O made.
More recently, Wicherts, Borsboom, & Dolan (later WBD) went into more detail on this point, writing, "Given the correlation between cranial capacity as measured externally and intelligence of around .20 (Rushton & Ankney, 2009), the Black-White gap in brain size cannot explain much of the IQ gap. Even if cranial capacity had a causal effect on g, then the Black-White gap in brain size cannot explain more than: .6*.2*15 = 1.8 IQ points. If we were to believe that the IQ gap between Africans and European Whites is 33 IQ points (Lynn & Vanhanen, 2006), then the brain size gap could explain a staggering 1.8/33 = 5% of the IQ gap. Thus, even under these terms, 95% of the IQ gap is left unexplained by brain size. With a correlation of .33 between brain volume and IQ as based on modern techniques (McDaniel, 2005), the gap in brain size can explain only 2.98 IQ points or 9% of the IQ gap."
The fourth assumption may be false as well. "It is not clear, however, that the relation between brain size and IQ is causal. There is conflicting evidence as to whether there is a correlation between siblings’ brain size and IQ" (Nisbett et al. 2012, p. 142).
So this leaves us at the fifth and last assumption. "Brain size differences between men and women are much greater than the race differences in brain size, yet men and women have the same average IQ" (Nisbett et al. 2012, p. 146). This point is also made by WBD, who note that "Another problem with the brain size hypothesis lies with the fact that sex differences in brain size are larger than race differences, yet studies involving representative samples, broad cognitive test batteries, and sound statistical methods consistently fail to show a clear sex difference in g."
Argument 2) Forensic anthropologists can identify race, therefore race is biologically real!
This argument is not uncommon, including from actual scientists, such as Sesardic (2010, p. 55), who wrote that "forensic anthropologists are quite successful in correctly inferring a person’s race from the skeletal characteristics of human remains". There are many situations in which race identification is used regularly in modern American society, such as to determine the race of a deceased individual in searching for their potential killer (Slate 2011). It has also been used to determine whether Kennewick Man was Caucasian, Asian, or something else entirely. (ABC News 2000). Given that this can be done pretty accurately, doesn't this prove that race exists?
No, partly because classifying people into groups from which individuals can be reliably identified leads to ridiculous categories--wayyyy more than just a couple "races" that are traditionally defined (Ousley et al. 2009). As Sauer (1992, p. 107) noted, "the successful assignment of race to a skeletal specimen is not a vindication of the race concept, but rather a prediction that an individual, while alive was assigned to a particular socially constructed ‘racial’ category". Ultimately, accurate assessment of race comes down to the information that the researcher has before making the assessment--without it the results can be ridiculously wrong (Konigsberg et al. 2009).
The traits used to identify remains of people from geographic regions (East Asia/Africa/Europe) aren't adaptive, they're totally random, as C. Loring Brace pointed out in 1995, when he wrote: "The significant identifying features of a given region then are stochastically determined and are not the products of natural selection. If they are valuable for purposes of identification, they have no coherent adaptive, that is, biological, significance."
Argument 3) It's always been this way!
Differential k theory, as defined by Rushton (1988), holds that not only can humans (yes, all of them) be classified into one of three races (namely, Mongoloids, Caucasoids, and Negroids), but also that these races consistently differ in multiple important respects, differences which cannot be explained by non-evolutionary/non-genetic factors. Problem is, the parameters being claimed to be due to evolution have changed WAAAY too fast to be due mostly, much less completely, to genetics. This is a problem because in order for these sorts of theories to be true, these parameters (fertility, IQ, infant mortality, etc.) should be pretty stable over enough time (at least many millennia for sure) for humans to evolve separately into distinct "races". Perhaps the best summary of evidence showing that it hasn't always been this way was provided by Weizmann et al. (1990), who noted in their paper's abstract that "Changes in human life-history traits are so rapid that there is no need to posit genetic selection to explain intergroup variation."
For instance, Rushton (1988, p. 11) wrote this of his theory's predictions: "...the more K the family the greater the spacing between births, the fewer the total number of offspring, the lower the rate of infant mortality, and the better developed the parental care." He goes on to claim that these predictions have been validated with the human species, and that the patterns just described are seen consistently when comparing Negroids (Africans), Caucasoids (Europeans), and Mongoloids (East Asians). As Wicherts et al. (2010) note, however, "In much of the twentieth century, fertility and infant mortality rates have been much higher in China than in European countries. This is inconsistent with Rushton’s assertion that East-Asians are more K-prone than Europeans." This is a similar conclusion to that reached in 1988 by Zuckerman and Brody, who noted that in Rushton's work, "Everything is assumed to be on a primarily genetic basis although sexual mores have shown remarkable changes in a single generation." Besides this, more recent evidence suggests that gestation time is longer, and maturation earlier, among whites than among Blacks or Asians (Patel et al. 2004). Recall that Rushton's theory claims that the order of gestation time is shortest in Blacks, longest in Asians, and intermediate in whites. Either his sources are outdated or they were never representative in the first place. Hmm...
Looking at IQ makes the problem of short-term change especially duh-obvious, given that the Flynn effect has been known to psychologists for over 30 years, and it has occurred on a huge scale (5 to 25 points/generation) (Flynn 1987). Wicherts et al. (2010) note that: "Knowing that national IQs can fluctuate by more than a standard deviation over 50 years, we may question the relevance of contemporary national IQs to peoples that lived thousands of years ago."
The best quote to close out this section came from Zuckerman (2003), who wrote that "To suggest that the behavior of modern descendents of these ancient regional ethnic groups is a function of evolved genetic mechanisms which are specific to their ancestry is not a plausible hypothesis. The more recent history of ethnic populations is much more relevant."
4. "The environment has nothing to do with it!"
The differences in gestation period discussed above are probably due to environmental factors, like disadvantage and discrimination (Sorbye et al. 2016). In any case, they don't seem to be due to genetic or normal sociodemographic factors (Migone et al. 1991).With regard to maturity, Mendle et al. (2007) noted that "Implicit in any discussion of racial differences in pubertal timing in American girls is the dangerous conflation of race with socioeconomic status. Socioeconomic status, and not race, affects known predictors of pubertal timing such as nutrition, environmental stress, and family composition. In fact, Obeidallah et al. (2000) established that documented differences in age of pubertal onset between Caucasian and Latina girls disappeared after controlling for socioeconomic status." Similar results for sexual behavior have been reported by Cunningham & Barbee (1991), who found that "...differences in black versus white birth rates were strongly associated with differences in infant mortality rates. As black infant mortality rates declined, black birth rates also declined at rates parallel to that of whites."
And this isn't even getting into the fact that the differences claimed to exist by hereditarians haven't been found in all studies on the subject, as Lynn (1989, p. 5) pointed out: "...a recent report to the National Academy of Sciences (Hayes, 1987) cites two sources reporting that sexually experienced blacks had intercourse slightly less often than whites (i.e., Zabin & Clark, 1981; Zelnick, Kantner, & Ford, 1981). In addition, there are apparently data inconsistent with Rushton and Bogaert’s (1987) claimed race differences in age at menarche. Gregerson (1982) reports that Cuban and Hong Kong girls have the earliest average age of menarche- just over 12 years-while the Greenland Eskimo. South African Bantu, and New Guinea Bundi have an average age at menarche of over 15 years. While these counterexamples and failures to replicate do not disprove Rushton and Bogaert’s (1987) claims, they do challenge the apparent unanimity of the findings reviewed by these authors and raise questions about the validity of the reported race differences."
Sources:
ABC News 2000: http://abcnews.go.com/Technology/story?id=98485&page=1
Brace 1995: https://www.astm.org/DIGITAL_LIBRARY/JOURNALS/FORENSIC/PAGES/JFS15336J.htm
Cain & Vanderwolf 1990: http://www.sciencedirect.com/science/article/pii/019188699090185T
Cernovsky 1993: http://philipperushton.net/wp-content/uploads/2015/02/iq-race-brain-size-rushton-cernovsky-j-of-black-psychology-1993.pdf
Cunningham & Barbee 1991: http://www.sciencedirect.com/science/article/pii/009265669190016J
Flynn 1987: http://www.jugendsozialarbeit.de/media/raw/flynn1987_What_IQ_tests_really_measure.pdf
Kamin & Omari 1998: http://journals.sagepub.com/doi/abs/10.1177/008124639802800301
Konigsberg et al. 2009: http://onlinelibrary.wiley.com/doi/10.1002/ajpa.20934/abstract
Lynn 1989: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.876.8834&rep=rep1&type=pdf
Mendle et al. 2007: http://www.sciencedirect.com/science/article/pii/S0273229706000773
Migone et al. 1991: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3016.1991.tb00724.x/abstract
Nisbett et al. 2012: https://www.apa.org/pubs/journals/releases/amp-67-2-130.pdf
Ousley et al. 2009: http://onlinelibrary.wiley.com/doi/10.1002/ajpa.21006/full
Patel et al. 2004: https://academic.oup.com/ije/article/33/1/107/668109
Rushton 1988: http://philipperushton.net/wp-content/uploads/2015/02/iq-race-brain-size-r-k-theory-sex-rushton-personality-individual-differences-1988.pdf
Rushton 1992: http://www.sciencedirect.com/science/article/pii/016028969290017L
Rushton 1994: http://www.sciencedirect.com/science/article/pii/0160289694900027
Rushton & Ankney, 1996: https://link.springer.com/article/10.3758/BF03210739
Rushton & Ankney, 2000: http://atavisionary.com/wp-content/uploads/2017/08/Size-matters-Rushton.pdf
Sesardic 2010: http://www.ln.edu.hk/philoso/staff/sesardic/Race.pdf
Slate 2011: http://www.slate.com/articles/news_and_politics/explainer/2011/01/alas_poor_yorick_or_is_it_othello.html
Sorbye et al. 2016: http://www.sciencedirect.com/science/article/pii/S1521693415001613
Weizmann et al. 1990: http://psycnet.apa.org/record/1991-07104-001
Weizmann et al.,1991: http://philipperushton.net/wp-content/uploads/2015/02/race-r-k-theory-rushton-weizmann-canadian-psychology-1-1991.pdf
Wicherts, Borsboom, & Dolan 2010: www.sciencedirect.com/science/article/pii/S0191886909003675
Winston 1996: http://philipperushton.net/wp-content/uploads/2015/02/iq-race-brain-size-rushton-winston-j-of-social-distress-the-homeless-4-1996.pdf
Zuckerman & Brody 1988: http://www.sciencedirect.com/science/article/pii/0191886988901365
Zuckerman 2003: www.sciencedirect.com/science/article/pii/S0191886902003628
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3016.1991.tb00724.x/abstract
http://www.nber.org/chapters/c6545.pdf
http://www.encyclopedia.com/social-sciences/encyclopedias-almanacs-transcripts-and-maps/forensic-anthropology-and-race
The second of these assumptions may also be false. As Nisbett et al. (2012, p. 146) noted, "Brain size of full-term Black and White infants is the same at birth, and several postnatal factors known to reduce brain size are more common for Blacks than for Whites."
What about the third?
Kamin & Omari (1998, later K&O) maintain that this assumption is false, writing: "Possible relations between head size and measured IQ are so small that they cannot possibly explain black-white differences in IQ." Rushton & Ankney (2000) responded by criticizing this review for four detailed reasons, as they outline in their paper's abstract. They go into a lot of detail arguing that K&O ignored "...the relation between brain size and IQ established by magnetic resonance imaging and the race differences in brain size established by MRI, autopsies, and endocranial volume". However, they do not seem AFAICT to address the "they're too small point" K&O made.
More recently, Wicherts, Borsboom, & Dolan (later WBD) went into more detail on this point, writing, "Given the correlation between cranial capacity as measured externally and intelligence of around .20 (Rushton & Ankney, 2009), the Black-White gap in brain size cannot explain much of the IQ gap. Even if cranial capacity had a causal effect on g, then the Black-White gap in brain size cannot explain more than: .6*.2*15 = 1.8 IQ points. If we were to believe that the IQ gap between Africans and European Whites is 33 IQ points (Lynn & Vanhanen, 2006), then the brain size gap could explain a staggering 1.8/33 = 5% of the IQ gap. Thus, even under these terms, 95% of the IQ gap is left unexplained by brain size. With a correlation of .33 between brain volume and IQ as based on modern techniques (McDaniel, 2005), the gap in brain size can explain only 2.98 IQ points or 9% of the IQ gap."
The fourth assumption may be false as well. "It is not clear, however, that the relation between brain size and IQ is causal. There is conflicting evidence as to whether there is a correlation between siblings’ brain size and IQ" (Nisbett et al. 2012, p. 142).
So this leaves us at the fifth and last assumption. "Brain size differences between men and women are much greater than the race differences in brain size, yet men and women have the same average IQ" (Nisbett et al. 2012, p. 146). This point is also made by WBD, who note that "Another problem with the brain size hypothesis lies with the fact that sex differences in brain size are larger than race differences, yet studies involving representative samples, broad cognitive test batteries, and sound statistical methods consistently fail to show a clear sex difference in g."
Argument 2) Forensic anthropologists can identify race, therefore race is biologically real!
This argument is not uncommon, including from actual scientists, such as Sesardic (2010, p. 55), who wrote that "forensic anthropologists are quite successful in correctly inferring a person’s race from the skeletal characteristics of human remains". There are many situations in which race identification is used regularly in modern American society, such as to determine the race of a deceased individual in searching for their potential killer (Slate 2011). It has also been used to determine whether Kennewick Man was Caucasian, Asian, or something else entirely. (ABC News 2000). Given that this can be done pretty accurately, doesn't this prove that race exists?
No, partly because classifying people into groups from which individuals can be reliably identified leads to ridiculous categories--wayyyy more than just a couple "races" that are traditionally defined (Ousley et al. 2009). As Sauer (1992, p. 107) noted, "the successful assignment of race to a skeletal specimen is not a vindication of the race concept, but rather a prediction that an individual, while alive was assigned to a particular socially constructed ‘racial’ category". Ultimately, accurate assessment of race comes down to the information that the researcher has before making the assessment--without it the results can be ridiculously wrong (Konigsberg et al. 2009).
The traits used to identify remains of people from geographic regions (East Asia/Africa/Europe) aren't adaptive, they're totally random, as C. Loring Brace pointed out in 1995, when he wrote: "The significant identifying features of a given region then are stochastically determined and are not the products of natural selection. If they are valuable for purposes of identification, they have no coherent adaptive, that is, biological, significance."
Argument 3) It's always been this way!
Differential k theory, as defined by Rushton (1988), holds that not only can humans (yes, all of them) be classified into one of three races (namely, Mongoloids, Caucasoids, and Negroids), but also that these races consistently differ in multiple important respects, differences which cannot be explained by non-evolutionary/non-genetic factors. Problem is, the parameters being claimed to be due to evolution have changed WAAAY too fast to be due mostly, much less completely, to genetics. This is a problem because in order for these sorts of theories to be true, these parameters (fertility, IQ, infant mortality, etc.) should be pretty stable over enough time (at least many millennia for sure) for humans to evolve separately into distinct "races". Perhaps the best summary of evidence showing that it hasn't always been this way was provided by Weizmann et al. (1990), who noted in their paper's abstract that "Changes in human life-history traits are so rapid that there is no need to posit genetic selection to explain intergroup variation."
For instance, Rushton (1988, p. 11) wrote this of his theory's predictions: "...the more K the family the greater the spacing between births, the fewer the total number of offspring, the lower the rate of infant mortality, and the better developed the parental care." He goes on to claim that these predictions have been validated with the human species, and that the patterns just described are seen consistently when comparing Negroids (Africans), Caucasoids (Europeans), and Mongoloids (East Asians). As Wicherts et al. (2010) note, however, "In much of the twentieth century, fertility and infant mortality rates have been much higher in China than in European countries. This is inconsistent with Rushton’s assertion that East-Asians are more K-prone than Europeans." This is a similar conclusion to that reached in 1988 by Zuckerman and Brody, who noted that in Rushton's work, "Everything is assumed to be on a primarily genetic basis although sexual mores have shown remarkable changes in a single generation." Besides this, more recent evidence suggests that gestation time is longer, and maturation earlier, among whites than among Blacks or Asians (Patel et al. 2004). Recall that Rushton's theory claims that the order of gestation time is shortest in Blacks, longest in Asians, and intermediate in whites. Either his sources are outdated or they were never representative in the first place. Hmm...
Looking at IQ makes the problem of short-term change especially duh-obvious, given that the Flynn effect has been known to psychologists for over 30 years, and it has occurred on a huge scale (5 to 25 points/generation) (Flynn 1987). Wicherts et al. (2010) note that: "Knowing that national IQs can fluctuate by more than a standard deviation over 50 years, we may question the relevance of contemporary national IQs to peoples that lived thousands of years ago."
The best quote to close out this section came from Zuckerman (2003), who wrote that "To suggest that the behavior of modern descendents of these ancient regional ethnic groups is a function of evolved genetic mechanisms which are specific to their ancestry is not a plausible hypothesis. The more recent history of ethnic populations is much more relevant."
4. "The environment has nothing to do with it!"
The differences in gestation period discussed above are probably due to environmental factors, like disadvantage and discrimination (Sorbye et al. 2016). In any case, they don't seem to be due to genetic or normal sociodemographic factors (Migone et al. 1991).With regard to maturity, Mendle et al. (2007) noted that "Implicit in any discussion of racial differences in pubertal timing in American girls is the dangerous conflation of race with socioeconomic status. Socioeconomic status, and not race, affects known predictors of pubertal timing such as nutrition, environmental stress, and family composition. In fact, Obeidallah et al. (2000) established that documented differences in age of pubertal onset between Caucasian and Latina girls disappeared after controlling for socioeconomic status." Similar results for sexual behavior have been reported by Cunningham & Barbee (1991), who found that "...differences in black versus white birth rates were strongly associated with differences in infant mortality rates. As black infant mortality rates declined, black birth rates also declined at rates parallel to that of whites."
And this isn't even getting into the fact that the differences claimed to exist by hereditarians haven't been found in all studies on the subject, as Lynn (1989, p. 5) pointed out: "...a recent report to the National Academy of Sciences (Hayes, 1987) cites two sources reporting that sexually experienced blacks had intercourse slightly less often than whites (i.e., Zabin & Clark, 1981; Zelnick, Kantner, & Ford, 1981). In addition, there are apparently data inconsistent with Rushton and Bogaert’s (1987) claimed race differences in age at menarche. Gregerson (1982) reports that Cuban and Hong Kong girls have the earliest average age of menarche- just over 12 years-while the Greenland Eskimo. South African Bantu, and New Guinea Bundi have an average age at menarche of over 15 years. While these counterexamples and failures to replicate do not disprove Rushton and Bogaert’s (1987) claims, they do challenge the apparent unanimity of the findings reviewed by these authors and raise questions about the validity of the reported race differences."
Sources:
ABC News 2000: http://abcnews.go.com/Technology/story?id=98485&page=1
Brace 1995: https://www.astm.org/DIGITAL_LIBRARY/JOURNALS/FORENSIC/PAGES/JFS15336J.htm
Cain & Vanderwolf 1990: http://www.sciencedirect.com/science/article/pii/019188699090185T
Cernovsky 1993: http://philipperushton.net/wp-content/uploads/2015/02/iq-race-brain-size-rushton-cernovsky-j-of-black-psychology-1993.pdf
Cunningham & Barbee 1991: http://www.sciencedirect.com/science/article/pii/009265669190016J
Flynn 1987: http://www.jugendsozialarbeit.de/media/raw/flynn1987_What_IQ_tests_really_measure.pdf
Kamin & Omari 1998: http://journals.sagepub.com/doi/abs/10.1177/008124639802800301
Konigsberg et al. 2009: http://onlinelibrary.wiley.com/doi/10.1002/ajpa.20934/abstract
Lynn 1989: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.876.8834&rep=rep1&type=pdf
Mendle et al. 2007: http://www.sciencedirect.com/science/article/pii/S0273229706000773
Migone et al. 1991: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3016.1991.tb00724.x/abstract
Nisbett et al. 2012: https://www.apa.org/pubs/journals/releases/amp-67-2-130.pdf
Ousley et al. 2009: http://onlinelibrary.wiley.com/doi/10.1002/ajpa.21006/full
Patel et al. 2004: https://academic.oup.com/ije/article/33/1/107/668109
Rushton 1988: http://philipperushton.net/wp-content/uploads/2015/02/iq-race-brain-size-r-k-theory-sex-rushton-personality-individual-differences-1988.pdf
Rushton 1992: http://www.sciencedirect.com/science/article/pii/016028969290017L
Rushton 1994: http://www.sciencedirect.com/science/article/pii/0160289694900027
Rushton & Ankney, 1996: https://link.springer.com/article/10.3758/BF03210739
Rushton & Ankney, 2000: http://atavisionary.com/wp-content/uploads/2017/08/Size-matters-Rushton.pdf
Sesardic 2010: http://www.ln.edu.hk/philoso/staff/sesardic/Race.pdf
Slate 2011: http://www.slate.com/articles/news_and_politics/explainer/2011/01/alas_poor_yorick_or_is_it_othello.html
Sorbye et al. 2016: http://www.sciencedirect.com/science/article/pii/S1521693415001613
Weizmann et al. 1990: http://psycnet.apa.org/record/1991-07104-001
Weizmann et al.,1991: http://philipperushton.net/wp-content/uploads/2015/02/race-r-k-theory-rushton-weizmann-canadian-psychology-1-1991.pdf
Wicherts, Borsboom, & Dolan 2010: www.sciencedirect.com/science/article/pii/S0191886909003675
Winston 1996: http://philipperushton.net/wp-content/uploads/2015/02/iq-race-brain-size-rushton-winston-j-of-social-distress-the-homeless-4-1996.pdf
Zuckerman & Brody 1988: http://www.sciencedirect.com/science/article/pii/0191886988901365
Zuckerman 2003: www.sciencedirect.com/science/article/pii/S0191886902003628
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3016.1991.tb00724.x/abstract
http://www.nber.org/chapters/c6545.pdf
http://www.encyclopedia.com/social-sciences/encyclopedias-almanacs-transcripts-and-maps/forensic-anthropology-and-race
