3050 words

Introduction

Psychologist J. P. Rushton was perhaps most famous for attempting to formulate a grand theory of racial differences. He tried to argue that, on a matrix of different traits, the “hierarchy” was basically Mongoloids > Caucasoids > Negroids. But Rushton’s theory was met with much force, and many authors in many of the different disciplines in which he derived his data to formulate his theory attacked his r/K selection theory also known as Differential K theory (where all humans are K, but some humans are more K than others, so some humans are more r than others). Nonetheless, although his theory has been falsified for many decades, did he get some things right about race? Well, a stopped clock is right twice a day, so it wouldn’t be that outlandish to believe that Rushton got some things right about racial differences, especially when it comes to physical differences. While we can be certain that there are physical differences in groups we term “racial groups” and designate “white”, “black”, “Asian”, “Native American”, and “Pacific Islander” (the five races in American racetalk), this doesn’t lend credence to Rushton’s r/K theory.

In this article, I will discuss Rushton’s claims on motor development between blacks and whites. I will argue that he basically got this right, but it is of no consequence to the overall truth of his grand theory of racial differences. We know that there are physical differences between racial groups. But that there are physical differences between racial groups doesn’t entail that Rushton’s grand theory is true. The only entailment, I think, that can be drawn from that is there is a possibility that physical differences between races could exist between them, but it is a leap to attribute these differences to Rushton’s r/K theory, since it is a falsified theory on logical, empirical and methodological grounds. So I will argue that while Rushton got this right, a stopped clock is right twice a day but this doesn’t mean that his r/K theory is true for human races.

Was Rushton right? Evaluating newer studies on black-white motor development

Imagine three newborns: one white, one black and the third Asian and you observe the first few weeks of their lives. Upon observing the beginnings of their lives, you begin to notice differences in motor development between them. The black infant is more motorically advanced than the white infant who is more motorically advanced than the Asian infant. The black infant begins to master movement, coordination and dexterity showing a remarkable level of motoric dexterity, while the white infant shows less motoric dexterity than the black infant, and the Asian infant still shows lower motoric dexterity than the white infant.

These disparities in motor development are evidence in the early stages of life, so is it genetic? Cultural? Bio-cultural? I will argue that what explains this is a bio-cultural view, and so it will of course eschew reductionism, but of course as infants grow and navigate through their cultural milieu and family lives, this will have a significant effect on their experiences and along with it their motoric development.

Although Rushton got a lot wrong, it seems that he got this issue right—there does seem to be differences in precocity of motor development between the races, and the references he cites below in his 2000 edition of Race, Evolution, and Behavior—although most are ancient compared to today’s standards—hold to scrutiny today, where blacks walk earlier than whites who walk earlier than Asians.

Rushton (2000: 148-149) writes:

Revised forms of Bayley’s Scales of Mental and Motor Development administered in 12 metropolitan areas of the United States to 1,409 representative infants aged 1-15 months showed black babies scored consistently above whites on the Motor Scale (Bayley, 1965). This difference was not limited to any one class of behavior, but included: coordination (arm and hand); muscular strength and tonus (holds head steady, balances head when carried, sits alone steadily, and stands alone); and locomotion (turns from side to back, raises self to sitting, makes stepping movements, walks with help, and walks alone).

Similar results have been found for children up to about age 3 elsewhere in the United States, in Jamaica, and in sub-Saharan Africa (Curti, Marshall, Steggerda, & Henderson, 1935; Knobloch & Pasamanik, 1953; Williams & Scott, 1953; Walters, 1967). In a review critical of the literature Warren (1972) nonetheless reported evidence for African motor precocity in 10 out of 12 studies. For example, Geber (1958:186) had examined 308 children in Uganda and reported an “all-round advance of development over European standards which was greater the younger the child.” Freedman (1974, 1979) found similar results in studies of newboms in Nigeria using the Cambridge Neonatal Scales (Brazelton & Freedman, 1971).

Mongoloid children are motorically delayed relative to Caucasoids. In a series of studies carried out on second- through fifth-generation Chinese-Americans in San Francisco, on third- and fourth-generation Japanese-Americans in Hawaii, and on Navajo Amerindians in New Mexico and Arizona, consistent differences were found between these groups and second- to fourth-generation European-Americans using the Cambridge Neonatal Scales (Freedman, 1974, 1979; Freedman & Freedman, 1969). One measure involved pressing the baby’s nose with a cloth, forcing it to breathe with its mouth. Whereas the average Chinese baby fails to exhibit a coordinated “defense reaction,” most Caucasian babies turn away or swipe at the cloth with the hands, a response reported in Western pediatric textbooks as the normal one.

On other measures including “automatic walk,” “head turning,” and “walking alone,” Mongoloid children are more delayed than Caucasoid children. Mongoloid samples, including the Navajo Amerindians, typically do not walk until 13 months, compared to the Caucasian 12 months and Negro 11 months (Freedman, 1979). In a standardization of the Denver Developmental Screening Test in Japan, Ueda (1978) found slower rates of motoric maturation in Japanese as compared with Caucasoid norms derived from the United States, with tests made from birth to 2 months in coordination and head lifting, from 3 to 5 months in muscular strength and rolling over, at 6 to 13 months in locomotion, and at 15 to 20 months in removing garments.

Regarding newer studies on this matter, there are differences between European and Asian children in the direction that Rushton claimed. Infants from Hong Kong displayed a difference sequence of rolling compared to Canadian children. There does seem to be a disparity in motoric development between Asian and white children (Mayson, Harris, and Bachman, 2007). These authors do cite some of the same studies like the DDST (which is currently outdated) which showed how Asian children were motorically delayed compared to white children. And although they put caution on their findings of their literature review, it’s quite clear that this pattern exists and it is a bio-cultural one. So they conclude their literature review writing “the literature reviewed suggests differences in rate of motor development among children of various ethnic origins, including those of Asian and European descent” and that “Limited support suggests also that certain developmental milestones, such as rolling, may differ between infants of Asian and European origin.” Further, cultural practices in northern China—for example, lying them on their backs on sandbags—stall the onset of walking in babies sitting, crawling, and walking by a few months (Karasik et al, 2011).

This is related to the muscles that are used to roll from a supine to prone position and vice versa. Since some Asian children spend a longer time in apparatuses that aren’t conducive to growing a strong muscular base to be able to roll from the supine to prone position, to crawl and eventually walk, this is the “cultural” in the “bio-cultural” approach I will argue for.

One study on Norwegian children found that half of the children were waking by 13 months (the median) while 25 percent were walking by 12 months and 75 percent were walking by 14 months (Storvold, Aarethun, and Bratberg, 2013). One reason for the delayed response time could be supine sleeping, which was put into effect during the Back to Sleep program to mitigate causes of death from SIDS. Although it obviously saved tens of thousands of infant lives, it came at a cost of slightly stunted motoric development. It also seems that there is poor predictive value for infant milestones such as walking when it comes to health (Jenni et al, 2012).

Black Caribbean, black African and Indian infants were less likely to show delays in gross motor milestones compared to white infants. But Pakistani and Bangladeshi infants were more likely to be delayed in motoric development and communicative gestures, which was partly attributed to socio-cultural factors (Kelly et al, 2006). Kelly et al (2006: 828) also warn against genetic conclusions based on their large findings of difference between white and African and Caribbean infants:

The differences we observed between Black African and Black Caribbean compared with White infants are large and remain unaffected after adjusting for important covariates. This makes it tempting to conclude that the remaining effect must be a consequence of genetic differences. However, such a conclusion would be prematurely drawn. First, we have not included the measurement of genetic factors in our analysis, and, therefore, the presence of such effects cannot be demonstrated. Second, speculating on such effects should only be done alongside recognition that the model we have been able to test contains imperfect measurement.

It has also been observed that black and white children achieved greater mastery of motoric ability (locomotor skills) compared to Asian children but there was no difference by age group (Adeyemi-Walker et al, 2018). It was also found that infants with higher motor development scores had a lower weight weight relative to their length as they grew. So it was found that delayed motor development was associated with higher weight relative to length (Shoaibi et al, 2018). Black infants are also more motorically advanced and this is seen at up to two years of age (Malina, 1988) while black children perform better on tests of motor ability than white children (Okano et al, 2001). Kilbride et al (1970) also found that Baganda infants in Uganda showed better motoric ability than white American children. Campbell and Heddeker (2001) also showed that black infants were more motorically advanced than infants of other races.

It is clear that research like this blows up the claim that there should be a “one-size fits all” chart for motoric development in infants and that there should be race-specific milestones. This means that we should throw out the WEIRD assumptions when it comes to motoric development of infants (Karasik et al, 2011). They discuss research in other cultures where African, Caribbean and Indian caregivers massage the muscles of babies, stretch their limbs, toss them in their air, sit them up, and walk with them while helping them which then shapes their muscles and has them learn the mind-muscle connections needed to be able to learn how to eventually walk. And it also seems that random assignment to exercise excelerates how quickly an infant walks. White infants also sit at 6 months while black infants sit at 4 months. Nonetheless, it is clear that culture and context can indeed shape motoric development in groups around the world.

A bio-cultural view of motor development

When it comes to biological influences on motor development, sex and age are two important variables (Escolano-Perez, Sanchez-Lopez, and Herrero-Nivela, 2021). Important to this, of course, is that the individual must be normal, and they must have a normal brain with normal vision and spatial skills. They must be able to hear (to eventually follow commands and hear what is going on in their environment to change their course of action if need be). Further, the child’s home environment and gestational age influence different portions of motoral development (Darcy, 2022). After infants begin crawling, their whole world changes and they process visual motion better and faster, being able to differentiate between different speeds and directions, so a stimulating environment for the infant can spur the development of the brain (Van der Meer and Van der Weel, 2022). Biological maturation and body weight also affect motor development. Walking develops naturally, but walking and motor competence need to be nurtured for the child to reach their full potential; lower motor competence is related to higher body weight (Drenowatz and Greier, 2019).

One study on Dutch and Israeli infants even found—using developmental niche construction—that “infant motor development indeed is at least partly culturally constructed [which] emphasizes the importance of placing infant motor development studies into their ‘cultural cradle‘ (Oudgeneong, Atun-Eni, and Schaik, 2020). Gross motor development—rolling over, crawling, alternating kicks, moving from lying to sitting, and having tummy time—is recognized by the WHO. Further, children from different cultures have different experiences, which also could lead to, for example, not doing things that are conducive to the development of gross motor development (Angulo-Barroso et al, 2010). Moreover, motor development is embodied, enculturated, embedded, and enabling (Adolph and Hoch, 2020). It is also known that differences in the cultural environment “have a non-negligible effect on motor development” (Bril, 1986). Motor development also takes place in physical environments and is purposive and goal-directed (Hallemans, Verbeque, and de Walle, 2020).

So putting this all together, we have conceptualized motor development as a dynamic process which is influenced by a complex interplay of biological and cultural factors (Barnes, Zieff, and Anderson, 1999). Biological factors like sex, age, health, sensory abilities, and socio-cultural factors like home environment and developmental niches explain motor development and differences in them between individuals. The cultural differences, though, can impede motoral development, and not allow one to reach milestones they would have otherwise reached in a different cultural environment, just like if one couldn’t hear or see would have trouble reaching developmental milestones.

Children of course grow up in cultural environments and contexts and so they are culturally situated. So what this means is that both the cultural and social environment the child finds themselves in will of course then influence their physical and mental development and lead them to their milestones they hit which is dictated by the normal biology they have which then is allowed by the socio-cultural environment they are born into. So we have the bio-cultural view on motor development, and beyond the cultural environment the child finds themselves in, the interactions they have between parents and caregivers—more knowledgeable others—can be pertinent to their motor development and reaching of developmental milestones. Cultural practices and expectations could emphasize certain milestones over others and then guide the child towards the trajectory. So the framework recognizes that normal biology and sensory perceptions are needed for the development of normal motor development, but that cultural and social differences in that context will spur motor development in the child who finds themselves in different cultures.

Conclusion

Was Rushton right about this? Yes, I think he was. The recent literature on the matter speaks to this. But that doesn’t mean that his r/K selection theory is true. There are differences in motor development between races. But what is interesting is the interaction between biological and cultural factors that spur motor development. The question of black motor precocity, however, is a socio-political question, since science is a social convention influenced by the values of the scientist in question. Now, to the best of my knowledge, Rushton himself never carried out studies on this, he just collated them to use them for his racial trait matrix. However, it’s quite clear that Rushton was politically politically and socially motivated to prove that his theory was true.

But physical differences between the races are easy enough to prove, and of course they are due to biological and cultural interactions. There are differences in skin color and their properties between blacks and whites (Campiche et al, 2019). There is a 3 percent center of mass difference between blacks and whites which explains why each race excels at running and swimming (Bejan, Jones, and Charles, 2010). There are differences in body composition between Asians and whites which means, at the same BMI, Asians would have thicker skin folds and higher body fat than whites (Wang et al, 1994; WHO expert consultation, 2004; Wang et al, 2011). Just like at the same BMI, blacks have lower body fat and thinner skin folds than whites (Vickery, Cureton, and Collins, 1988; Wagner and Heyward, 2000; Flegal et al, 2010). There are differences in menarche and thelarche between blacks and whites (Wagner and Heyward, 2000; Kaplowitz, 2008; Reagan et al, 2013; Cabrera et al, 2014; Deardorff et al, 2014; ). There are differences in anatomy and physiology and somatotype between blacks and whites and these differences would explain how the races would perform on the big four lifts. There are interesting and real physical differences between races.

So obviously, what is considered “normal” is different in different cultures, and motor development is no different. So just like I think we should have different BMI and skin fold charts for different races, so too should we have different developmental milestones for different races and cultures. The discussion here is clear, since what is “average” and “normal” is different based on race and culture. Like for instance, black babies begin walking around 11 months, white babies around 12 months and Native American babies at 13 months. So while parents may be worried that their child didn’t hit a certain developmental milestone like walking, sitting, rolling, taking a bio-cultural approach will assuage these worries.

Nonetheless, while Rushton was right about race and motor development, we need to center his research project in context. He was clearly motivated, despite the numerous and forceful critiques of his framework, to prove that he was right. But the continuance of Rushton pushing his theory up until his death shows me that he was quite obviously socially and politically motivated, contrary to what he may have said.

We have approached this paper from the stance that science is a social activity, with all observations influenced by, as well as reflective of, the values of scientists and the political leanings of the sociocultural context within which research is conducted. We suggest that when questions of group difference are pursued in science, awareness of how the categories themselves have been shaped by social and historical forces, as well as of the potential effects on society, is important. (Barnes, Zieff, and Anderson, 1999)