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Black-White Differences in Bone Density

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I have written a few response articles to some of what Thompson has written over the past few years. He is most ridiculous when he begins to talk about nutrition (see my response to one of his articles on diet: Is Diet An IQ Test?). Now, in a review of Angela Saini’s (2019) new book Superior: The Return of Race Science, titled Superior Ideology, Thompson, yet again, makes more ridiculous assertions—this time about bone density as an adaptation. (I don’t care about what he says about race; though I should note that the debate will be settled with philosophy, not biology. Nor do I care about whatever else he says, I’m only concerned with his awful take on anatomy and physiology.)

The intellectually curious would ask: are there other adaptations which are not superficial? How about bone density?

https://academic.oup.com/jcem/article/82/2/429/2823249
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1863580/

Just-so story incoming.

I’m very familiar with these two papers. Let’s look at them both in turn.

The first study is Racial Differences in Bone Density between Young Adult Black and White Subjects Persist after Adjustment for Anthropometric, Lifestyle, and Biochemical Differences (Ettinger et al, 1997). Now, I did reference this article in my own piece on racial differences in drowning, though only to drive home the point that there are racial differences in bone density. Thompson is outright using this article as “evidence” that it is an adaptation.

In any case, Ettinger et al (1997) state that greater bone density in blacks may be due to differences in calciotropic hormones—hormones that play a major role in bone growth and bone remodeling. When compared with whites “black persons have lower urinary calcium excretion, higher 1,25-dihydroxyvitamin D (1, 25D) level, and lower 25-hydroxyvitamin D (25D) and osteocalcin level (9)” (Ettinger et al, 1997). They also state that bone density can be affected by calcium intake, physical activity, They also state that testosterone (an androgen) may account for racial and gender differences in bone density, writing “Two studies have demonstrated statistically significantly higher serum testosterone level in young adult black men (22) and women (23).”

Oh, wow. What are refs [22] and [23]? [22] is one of my favorites—Ross et al (1986) (read my response). To be brief, the main problems with Ross et al is that assay times were all over the place, along with it being a small convenience sample of 50 blacks and 50 whites. LabTests Online writes that it is preferred to assay in the morning while in a fasted state. In Ross et al, the assay times were between 10 am and 3 pm, which was a “convenient time” for the students. Along with the fact that the sample was small, this study should not be taken seriously regarding racial differences in testosterone, and, thus, racial differences in bone density.

Now what about [23]? This is another favorite of mine—Henderson et al (1988; of which Ross was a part of). Mazur (2016) shows that black women do not have higher levels of testosterone than white women. Furthermore, this is just like Ellis’ (2017) claims that there is a difference in prenatal androgen exposure, but that claim, too, fails. In any case, testosterone can’t explain differences in bone density between races.

Ettinger et al (1997) showed that blacks had higher levels of bone density than whites in all of the sites they looked at. (Though they also used skin-fold testing, which is notoroiously bad at measuring body composition in blacks; see Vickery, Cureton, and Collins, 1988). However, Ettinger et al (1997) did not claim, nor did they imply that bone density is an adaptation.

Now, getting to the second citation, Hochberg (2007). Hochberg (2007) is a review of differences in bone mineral density (BMD) between blacks and whites. Unfortunately, there is no evidence in this paper, either, that BMD is an adaptation. Hochberg (2007) gives numerous reasons why blacks would have stronger skeletons than whites, and neither is that they are an “adaptation”:

Higher bone strength in blacks could be due to several factors including development of a stronger skeleton during childhood and adolescence, slower loss of bone during adulthood due to reduced rates of bone turnover and greater ability to replace lost bone due to better bone formation. Bell and colleagues reported that black children had higher bone mass than white children and that this difference persisted into young adulthood, at least in men (,). Development of a stronger skeleton during childhood and adolescence is dependent on the interaction of genetic and environmental factors, including nutrition and lifestyle factors ().

[…]

Genetic, nutritional, lifestyle and hormonal factors may contribute to differences in rates of bone turnover during adulthood

There are numerous papers in the literature that show that blacks have higher BMD than whites and that there are racial differences in this variable. However, the papers that Thompson has cited are not evidence. That trait T exists and there is a difference in trait T between G1 and G2 does not license the claim that the difference in trait T between G1 and G2 is “genetic.”

Thompson then writes:

Equally, how about differences in glomerular function, a measure of kidney health, for which the scores are adjusted for those of Black African descent, to account for their higher muscle mass? Muscle mass and bone density are not superficial characteristics. In conflicts it would be a considerable advantage to have strong warriors, favouring “hard survival”.

Here’s the just-so story.

Race adjustment for estimating glomerular filtration rate (GFR) is not always needed (Zanocco et al, 2012). Renal function is measured by GFR. Renal function is an indication of the kidney’s functioning. Racial differences in kidney function exist, even in cases where the patients do not have CKD (chronic kidney disease) (Peralta et al, 2011). Black Americans also constitute 35 percent of all patients in America receiving kidney dialysis, despite being only 13 percent of the US population. Blacks do generate higher levels of creatinine compared to whites, and this is due to higher average muscle mass when compared with whites.

There are differences in BMD and muscle mass between blacks and whites which is established by young adulthood (Popp et al, 2017), but the claim that there trait T is an adaptation because trait T exists and there is a difference between G1 and G2 is unfounded. It’s simply a just-so story, using the old EP reverse engineering. The two papers referenced by Thompson are not evidence that the BMD is an adaptation, it only shows that there are racial differences in the trait. That there are racial differences in the two traits does not license the claim that the traits in question are an adaptation as Thompson seems to be claiming. The papers he refers to only note a difference between the two groups; it does not discuss the ultimate etiology of the difference between the groups, which Thompson does with his just-so story.

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2 Comments

  1. Phil78 says:

    This is pretty easy to resolve. In the anthropological record, modern reduced BMD occurred alongside sedentary farming, which is obvious by comparing contemporaneous HG populations to them.

    AS A farmees, however, in their origins in the Sahel as either HG or Pastoralists practice agro-pastoralism and shifting cultivation. The Guinea was somewhat varied but still shifted.

    In the forest, becoming farmers as well, I believed were still decentralized for a while and would become more mobile during the Bantu expansion.

    Therefore, a more mobile living retained more BMD, but thus really isn’t an adaptation but more of a preservation of human BMD variation. Reduced BMD can’t really be said to be much of an advantage as much of a result of a lack of fixation.

    This is embarrassing on Thompson’s behalf.

    Like

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