The modernity mess

When we had the good fortune to study the Klasies River Mouth Cave remains at the South African Museum in 1989, the isolated partial zygomatic KRM 16651 presented us with a morphometric challenge. The face of the bone appeared quite large, but only a small portion of the inferior border was preserved, and that mostly under the temporal process. No measuring points allowed standard comparisons to be made for the size of the zygomatic face. However, comparing it with other more complete specimens, we felt a conservative interpretation placed the inferior edge of the medial break close to the zygomaxillary suture (the interpretation is conservative because if we assumed the break was further from the suture, the size of the bone we estimated would be larger). The orbital rim, zygofrontal suture, jugal notch, and superior zygotemporal suture allowed us to place the fragment on complete specimens in proper orientation; we used the crania of our comparative sample of Holocene populations from the Southern Cape, and casts of African fossils. We did not want to guess at the position of the zygomaxillare (zm) point, so instead we knowingly underestimated the vertical distance of that point to the orbital rim, in Frankfurt Horizontal, by taking the vertical distance from the most inferior point of the bone. We knew this would underestimate the true measurement that would be taken had the zm point been preserved. We did this a number of times, using different specimens for orientation, and recorded (and reported) a distance of greater than 30 mm. With assertions and figures, Bräuer & Singer (1996) argue this is incorrect and that the specimen is much smaller. This is important in their train of evidence that Klasies is an anatomically modern human sample. We did not mismeasure or misreport, and although we do not believe that the size of the zygomatic face is critical in considering whether the Klasies sample is modern, we want to briefly show why our anatomical assessment is the correct one. To avoid problems of picturing specimens to different scales, or in different orientations, we present in our figure, a picture of the KRM 16651 cast, in the same frame as a cast of the left zygomatic for Kabwe, cut to present the same portion as the Klasies specimen preserves. According to the data reported by Bräuer & Singer, Kabwe is larger than the Klasies specimen; according to the results of our measurements it is smaller. Although we usually abhor this phrase, the figure speaks for itself. We hope focus can now return to the real question—the modernity of the Klasies sample. This question can not be separated from a deeper one—what does it mean to be modern?—the question that is at the heart of these human origins debates. Because it is variable, the interpretation of the Klasies sample is entirely dependent on what one thinks ‘‘modernity’’ is, and, therefore, there is a real danger of circularity if the broader issue is not reckoned with. Even if we concentrate on the putative modern features at Klasies, absence of supraorbitals for KRM 16425 (though it is possible that the specimen is juvenile) and the chin of KRM 41815 [though it might be an artefact of a strong incisure (the concave area on the symphysis