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Comment on “The growth pattern of Neandertals, reconstructed from a juvenile skeleton from El Sidrón (Spain)”

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Science  09 Mar 2018:
Vol. 359, Issue 6380, eaar3611
DOI: 10.1126/science.aar3611

Figures

  • Fig. 1 Neandertal brain size evolution.

    Adult is known for 26 Neandertals (blue circles). Notice that there is a slight but statistically significant (r = 0.49, P = 0.006) increase in brain size over the course of Neandertal evolution. El Sidrón J1 (red ×) falls comfortably within the range of adult cranial capacities in late Würm Neandertals.

  • Fig. 2 El Sidrón J1 relative brain size.

    The cranial capacity of El Sidrón (1330 cc) was divided by all adult Neandertal cranial capacities to calculate a percentage of adult brain size achieved by the age of the individual’s death (7.7 years). The mean value (black square) is plotted along with the 95% confidence interval of the mean (gray bars). Note that the percentage of brain size achieved at death in a similarly aged modern human (95 to 100%; green highlighted range) either encompasses the mean (for all Neandertals) or very nearly does. These data suggest that El Sidrón J1 had achieved significantly more of its adult cranial capacity than the 87.5% reported by Rosas et al. (1), and likely had little remaining brain growth.

  • Fig. 3 Neandertal brain ontogeny.

    El Sidrón J1 is one of 13 known juvenile Neandertal crania (Table 1). Developmental ages of these individuals were based on data in (1, 8, 13, 14). These juvenile cranial capacities were each divided by the 18 Würm + Krapina adult cranial capacities to calculate a Neandertal brain growth curve. Error bars indicate 95% confidence interval of the mean of the percentage of brain growth achieved by that chronological age in Neandertals and modern humans. Human data were drawn from (15). Notice the similarities between human and Neandertal brain development [see also (9)]. Although El Sidrón J1 is slightly smaller than expected, in this broader context it appears best interpreted as normal variation in Neandertals. Accepting the premise that El Sidrón J1 (at age 7.7 years) is evidence for extended brain growth in the Neandertals would also necessitate accepting that Neandertals essentially ceased brain growth between the ages of 3 and 7.7 years, only to resume again.

Tables

  • Table 1 Neandertal cranial capacities.

    Würm Neandertals (living <115,000 years ago) are in italics. Cranial capacities are from (1, 7, 1113).

    SpecimenCranial capacityDevelopmental agePercent of El Sidrón
    juvenile cranial capacity
    Saccopastore 11174Adult113.3
    Saccopastore 21300Adult102.3
    Reilingen1430Adult93.0
    Biache1200Adult110.8
    Apidima 21454Adult91.5
    Fontechevade II1350Adult98.5
    La Chaise1065Adult124.9
    Lazaret1250Subadult106.4
    Krapina 112936 to 8 years
    Krapina 21450Subadult91.7
    Krapina 31255Adult106.0
    Krapina 51535Adult86.6
    Krapina 61205Adult110.4
    Tabun C11271Adult104.6
    Subalyuk11873.2 years
    Ganovce1320Adult100.8
    Teshik-Tash1525~9 years
    Roc de Marsal13253 years
    La Ferrassie1640Adult81.1
    Spy I1305Adult101.9
    Spy II1553Adult85.6
    La Quina 51172Adult113.5
    La Quina 1812006 to 8 years
    Mezmaiskaya429Infant
    Engis 213623.2 years
    Shanidar 11600Adult83.1
    Shanidar 51550Adult85.8
    Monte Circeo1360Adult97.8
    Gibraltar–Devil’s Tower14004.6 years
    Gibraltar–Forbes Quarry1200Adult110.8
    La Chapelle1625Adult81.9
    El Sidrón J113307.7 years
    Dederiyeh 110961.55 years
    Dederiyeh 210892.0 years
    Pech de l’Aze11352.5 years
    Amud1740Adult76.4
    Le Moustier 11565Subadult85.0
    Le Moustier 2418Infant
    Feldhofer1525Adult87.2

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