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hypothesis that the marks on the fossil bones of Balaenotus had been produced by the teeth of sharks. “In the first place,” he said, “it is evident that the marks shown to us have been produced by cutting. All the world agrees on this point. We are only discussing the question of whether these cuts were made by the sharp pointed teeth of sharks or by the human hand armed with sharp flint. There is another point which seems to me incontestable. That is that all the incisions, in their diverse forms, those perpendicular as well as oblique, can be easily reproduced, with all their characteristics, with a flint implement on fresh whale bones. The hypothesis of Capellini explains very well the observed facts, while the other hypothesis encounters very strong objections. Capellini has remarked with reason that every bite should produce two imprints corresponding to the two jaws that seize the bone at two opposite points. But without exception all the incisions are on the convex surface of the ribs, with the concave surface totally exempt from all markings. I do not believe that one can respond to this argument” (Capellini 1877, p. 58).

Here Broca seems to be thinking that the shark would completely devour the whale carcass, thus breaking apart the rib cage. Given the feeding frenzies of sharks, especially the great white shark, present in the Pliocene as Cacharodon megalodon, one might expect this to happen. Otherwise, it is difficult to see how the shark could place bite marks on both sides of the rib.

Some years later, de Mortillet (1883, p. 62) suggested, in Le Préhistorique, that the particular nature of a shark’s jaw and method of biting would result in tooth marks being placed on only one side of a bone subjected to its attack. As usual, however, de Mortillet only painted speculative scenarios and did not present any hard experimental evidence.

Broca continued: “Among the incisions, the majority penetrate obliquely into the bone. One of the sides of the V-shaped incision slices into the bone at a small angle, departing only slightly from the horizontal plane of the surface of the bone; while the opposite side, shorter than the first, is abrupt, almost vertical. The incision shows breakage. That is to say, the cutting action results in the separation of a small shaving of bone, broken at its base [Figure 2.1]. The cutting action of a sharp edge produces marks of this type. I don’t believe that the teeth of any animal could produce the same effect” (Capellini 1877, p. 58). The same thing was admitted by de Mortillet himself, who raised the point in his discussion of the bones of St. Prest (Section 2.1).

“Finally,” said Broca, “—and I insist on this point, which Capellini touched upon only lightly—the direction of certain of the marks is incompatible with the idea of a bite. The jaws do not execute such a movement. They open and they close.

The sort of curve described by a tooth rests always on the same plane. The incision produced by a pointed tooth on a hard surface, convex and immobile, is of determinate form. It is that of a plain curve, from one point to another by the shortest path, like a meridian on the surface of a sphere. The majority of incisions before our eyes do not present such a character. Here is one among others in which the direction changes many times [ Figure 2.2]. . . . the whole incision is made up, first, of a path perpendicular to the axis of the rib, then another longitudinal path, and finally an oblique one. It is a turning movement that a jaw could not make. The human hand, on the contrary, is capable, because of its multiple articulations, of perfect mobility, of guiding and inclining in every direction over the surface the instruments with which it is armed” (Capellini 1877, pp. 58–59).

Figure 2.2. A Pliocene whale scapula from Monte Aperto, Italy, with cut marks similar to those described by Broca (de Quatrefages 1887, p. 97).

Even though there may be some justification for pursuing the shark hypothesis with regard to the markings on the Pliocene whale bones of Italy, there is no reason