Krapina atlases suggest a high prevalence of anatomical variations in the first cervical vertebra of Neanderthals

Abstract

The first cervical vertebra, atlas, and its anatomical variants have been widely studied in Homo sapiens. However, in Neanderthals, the presence of anatomical variants of the atlas has been very little studied until very recently. Only the Neanderthal group from the El Sidrón site (Spain) has been analysed with regard to the anatomical variants of the atlas. A high prevalence of anatomical variants has been described in this sample, which points to low genetic diversity in this Neanderthal group. Even so, the high prevalence of anatomical variations detected in El Sidrón Neanderthal atlases needs to be confirmed by analysing more Neanderthal remains. In this context, we analysed the possible presence of anatomical variants in the three Neanderthal atlases recovered from the Krapina site (Croatia) within the Neanderthal lineage. Two of the three Krapina atlases presented anatomical variations. One atlas (Krapina 98) had an unclosed transverse foramen and the other (Krapina 99) presented a non‐fused anterior atlas arch. Moreover, an extended review of the bibliography also showed these anatomical variations in other Middle and Upper Pleistocene hominins, leading us to hypothesise that anatomical variations of the atlas had a higher prevalence in extinct hominins than in modern humans.

Comment on ‘Krapina atlases suggest a high prevalence of anatomical variations in the first cervical vertebra of Neanderthals’

“…For instance, in Figure 2b it can be observed the difference in texture between the cortical bone (C) and the porous-like surface (P), indicating that the gap in this atlas should be considered an unfused AS. Although difficult to observe in Figure 2E and 3B from Palancar et al (2020) due to image resolution, the authors noted the presence of this porous-like surface in Kr.99, which would indicate the presence of an unfused AS.…”

“…Based on the graphic information provided by Palancar et al (2020), it is our opinion that Kr.99 represents a juvenile atlas with an unfused anterior synchondrosis (AS), and not an adult atlas with an anterior cleft.…”

“…For comparative purposes, we provide an ontogenetic series of the normal shape changes of the left AS inFigure 1.The clear delimitation of the AS in Kr.99 (Figure 2EandFigure 3B,Palancar et al, 2020) is quite similar to the AS of case E, indicating the presence of a non-fused AS. While the contour of the superior articular facet in Kr.99 seems to be less well marked than in the Kr.98 adult atlas, suggesting that the individual is not fully mature,Palancar et al (2020) might have been confused by the overall mature morphology of Kr.99. The shape and location of the AS might have also confused the interpretation about the maturity status of Kr.99.…”

“…The macroscopic aspect of the presumed defect of the anterior arch (Figure 2Dand E,Palancar et al, 2020) presents the partially flattened surface and well-defined perimeter of an anterior synchondrosis (AS) in the last stages before fusion with the anterior arch. For comparative purposes, we provide an ontogenetic series of the normal shape changes of the left AS inFigure 1.The clear delimitation of the AS in Kr.99 (Figure 2EandFigure 3B,Palancar et al, 2020) is quite similar to the AS of case E, indicating the presence of a non-fused AS. While the contour of the superior articular facet in Kr.99 seems to be less well marked than in the Kr.98 adult atlas, suggesting that the individual is not fully mature,Palancar et al (2020) might have been confused by the overall mature morphology of Kr.99.…”

Response to Letter to the Editor by Dr Rios and Dr Cardoso

“…We have read with interest the letter of Dr Rios and Dr Cardoso about our manuscript entitled “Krapina atlases suggest a high prevalence of anatomical variations in the first cervical vertebra of Neanderthals,” by Palancar et al . (2020). Dr Rios and Dr Cardoso wrote in their letter that Kr.99 probably corresponds to a “ late juvenile atlas vertebra” with a non‐fused anterior synchondrosis, instead of an adult with a cleft, as proposed in our research.…”