Racial variation in some parts of the skull involved in chewing
At some point, our ancestors made the switch to eating cooked food. This allowed people to get by with a less robust chewing apparatus, and the chewing apparatus did indeed become less robust. Therefore, an examination of racial variation in the chewing apparatus will surely reveal some interesting aspects of racial history.
First, we consider some parts of the skull under selection pressures related to chewing (Figure 1; see legend for details). Selection pressures refer to forces constraining trait variation.
Figure 1: Some parts of the skull under selection pressures related to chewing. The involvement of the teeth should be obvious. The red ellipses mark the regions of attachment of a major muscle involved in shutting the jaw, i.e., the masseter, which attaches to parts of the cheekbones (zygomatic bones; also known as malars), the zygomatic arches (the posterior bony arches attached to the zygomatics) and the mandible (lower jaw). The green outline marks the area over which the temporalis muscle is spread; the temporalis passes underneath the zygomatic arch.
It should be obvious that our primitive ancestors who ate raw food only would have required larger teeth. They would also have needed larger chewing muscles, larger areas for attaching chewing muscles to bones, and thereby larger bones involved in the support of chewing. As should be clear from Figure 1, they would have had larger cheekbones. Additionally, breadth “b” in Figure 1 describes the breadth of the attachment of the masseter to the lower jaw bone (mandible), and this breadth would have been larger to accommodate a larger masseter. Obviously, if one were to increase breadth “b,” the jaw would end up protruding more. Indeed, all apes and monkeys have more protrusive jaws than humans. Further, the zygomatic arches couldn’t be too flattened or else there would not be much space for a large temporalis muscle to pass beneath the arches.
With the background above, we can now address racial variation. Let us consider cheekbones first. I have previously cited formal evidence that the cheekbones of whites are smaller, on average, than those of non-whites, especially Mongoloids, Negroids and Australian aboriginals; see Figures 9 and 10 here, and this should be common observation. Hybrid populations with Caucasian admixture—such as Hindoos—also have more prominent cheekbones than whites, on average, likely due to major Australoasiatic genetic influence among Hindoos.
Next, we consider the mandible (lower jaw). Figure 2 shows mandibular variation across some major races.
It is clearly seen from Figure 2 that whites have, on average, smaller mandibles than Negroes and Mongoloids. Australian aboriginals also have larger mandibles than whites; see, for example, the two pictures at the bottom right of Figure 7 here. Figure 2 also shows that the order of jaw protrusion is Negro > Mongoloid > white. Although the lower jaw is smaller in whites than in other races, whites have better chin development than non-whites, and this is something that I will properly address later on.
In Figure 3 below, note that although the woman on the left has a small lower jaw, the shape of her lower jaw is not very European-looking due to a weak chin and a strong angle of the mandible. The angle of the mandible is formed by the vertical and horizontal parts of the mandible at the gonion (labeled in Figure 5); see Figure 2 for racial variation in the angle of the mandible.
In Figure 4 below, note that the angle of the mandible is so altered that the jawline approaches a smooth curve, and the chin is better developed than that of the woman on the left in Figure 3.
Next, we apply the knowledge above to European aesthetics; see Figure 5 in this regard.
Attractive whites should have chin length greater than the average for non-whites; mandibular body length shorter than the average for non-whites; the angle at the gonion, also known as the angle of the mandible, less sharp than the average for non-whites; and cheekbones that are smaller than the average for non-whites. In the event that these requirements are not obvious, the following images should suffice to convince.
In Figure 6 below, contrast the beastly appearance of Maria Shriver—thanks to her remarkably primitive mandible and zygomatics—to that of the fine-featured woman on the right and the fine-plus-soft-featured woman at the bottom. Primitive means ancestral, not inferior.
Figure 7 shows cheekbone variation among white women, ranging from the extremely primitive to the normal.
Figure 8 shows mandible variation, ranging from the extremely primitive to the normal.
Artists often possess a sophisticated aesthetic sense, and when asked to sketch realistic portraits of attractive white women, do not sketch cheekbones and jawlines that look primitive (Figure 9).
Since there is a normal range of mandible variation among whites (Figure 2), the aesthetic range of mandible variation among whites is the subset of the normal range that is less primitive and thereby more European. It is easy to picture that if one were to extend the “Europeanization” of the mandible to a point where the mandible goes outside the normal range of mandible variation among whites, then the mandible will become less attractive, and a similar idea applies to zygomatic variation. Therefore, one of the selective forces constraining skeletal size and shape variation is sexual selection, which refers to the tendency to mate with partners that one finds sexually appealing and avoid partners that one finds sexually unappealing.
Compared to apes, the gracilization in humans of the skeletal structures that support chewing has a straightforward explanation. Before the transition to eating cooked food, those with less robust chewing structures would have a more difficult time obtaining adequate nutrition, but the transition to cooking made it easier for these individuals to obtain adequate nutrition. Add in the possibility of a greater prevalence of some Darwinian-fitness-enhancing factors among those with less robust chewing structures and a visual aesthetic bias toward less robust facial features, then given enough generations, one will obtain a more gracile chewing apparatus. However, how does one explain the racial differences? One possibility is that the ancestors of whites made the transition to eating cooked food before the ancestors of non-whites did. Another possibility is that all human populations made the transition to eating cooked food at the same time, but either sexual selection operated more strongly among Europeans or sexual selection operated equally strongly among all human populations but the non-Europeans had less of a visual aesthetic bias toward less robust facial features. Looking at racial variation in overall tooth size will partly help address this question since one does not normally examine tooth size before mating with someone. Figure 10 shows population variation in overall tooth size.
Figure 10 shows that the smallest teeth are present among whites, Ainus and Negritos. Since the Negritos are practically dwarves compared to whites, their teeth are larger than whites relative to body size. Hindoo tooth size lies toward the higher end of white tooth size, but then Hindoos have Caucasian admixture and are physically smaller than whites, and Hindoos in southern India are smaller than Hindoos in Northern India; i.e., Hindoos have larger teeth—with respect to body size—than whites, on average. Since a major contribution to the Hindoo gene pool is Australoasiatic and S.E. Asians and Australian aboriginals have larger teeth than Hindoos (except Negritos), the smaller teeth among Hindoos compared to their Asiatic neighbors appear to be a result of Caucasian admixture. The smaller teeth of the Somalis among black Africans appear to be a result of non-Negroid admixture. Indeed, the residents of Eastern Africa thousands of years ago were not a Negroid people. 
Figure 10 strongly suggests that Europeans and the Ainus of Japan were the first people to transition to eating cooked food, which is confirmed by archeological evidence.  The question of the intensity of sexual selection across different populations cannot be answered within this post, but one can likely rule out the possibility than non-whites have less of a visual aesthetic bias toward gracile facial features. Indeed, Negroids and Mongoloids passed off as attractive by Negroids and Mongoloids, respectively, are farther removed—in the direction of gracility—from the average of jaw and cheekbone structures in their respective populations than attractive whites are with respect to the average of these structures in Northern Europe.
Therefore, it appears that a major factor that explains the racial differences in some parts of the skull involved in chewing is that Europeans made an earlier transition to cooking food than non-Europeans did (except the Ainus, who have more Caucasoid facial features than the typical Japanese), likely because they along with the Ainus were the first people to produce humans intelligent enough to tame fire and put it to practical use.
The discussion above allows us to partly answer a question previously asked by Svigor:
Well, masculinization sharpens the angle of the mandible,  and a sharper angle of the mandible is also a primitive trait (Figures 1 and 2). Additionally, more robust zygomatics/zygomatic arches and more robust mandibles (excluding the chin) add ruggedness to the face, happen to be more primitive traits and are disproportionately more characteristic of non-whites. Therefore, part of what appears to be greater facial masculinity among non-white women to Svigor and undoubtedly many others is not higher masculinization among them but simply greater retention of primitive and thereby robust facial features.
Once again, it should be clear that race mixing will not be enhancing the beauty of the most attractive whites; see Figure 11 in this regard and think about the possibility of race mixing producing the facial structures shown in Figure 9.
1. Bastir M, Rosas A, Kuroe K: Petrosal orientation and mandibular evidence for an integrated petroso-developmental unit. American Journal of Physical Anthropology 2004, 123:340-350.
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