Evolutionary Biology

, Volume 41, Issue 4, pp 572–594

A Shared Pattern of Postnatal Endocranial Development in Extant Hominoids

  • Nadia Scott
  • Simon Neubauer
  • Jean-Jacques Hublin
  • Philipp Gunz
Research Article

DOI: 10.1007/s11692-014-9290-7

Cite this article as:
Scott, N., Neubauer, S., Hublin, JJ. et al. Evol Biol (2014) 41: 572. doi:10.1007/s11692-014-9290-7

Abstract

By comparing species-specific developmental patterns, we can approach the question of how development shapes adult morphology and contributes to the evolution of novel forms. Studies of evolutionary changes to brain development in primates can provide important clues about the emergence of human cognition, but are hindered by the lack of preserved neural tissue in the fossil record. As a proxy, we study the shape of endocasts, virtual imprints of the endocranial cavity, using 3D geometric morphometrics. We have previously demonstrated that the pattern of endocranial shape development is shared by modern humans, chimpanzees and Neanderthals after the first year of life until adulthood. However, whether this represents a common hominoid mode of development is unknown. Here, we present the first characterization and comparison of ontogenetic endocranial shape changes in a cross-sectional sample of modern humans, chimpanzees, gorillas, orangutans and gibbons. Using developmental simulations, we demonstrate that from late infancy to adulthood ontogenetic trajectories are similar among all hominoid species, but differ in the amount of shape change. Furthermore, we show that during early ontogeny gorillas undergo more pronounced shape changes along this shared trajectory than do chimpanzees, indicative of a dissociation of size and shape change. As shape differences between species are apparent in even our youngest samples, our results indicate that the ontogenetic trajectories of extant hominoids diverged at an earlier stage of ontogeny but subsequently converge following the eruption of the deciduous dentition.

Keywords

Endocranium Virtual endocast Evolutionary development Hominoid Heterochrony Geometric morphometrics 

Supplementary material

11692_2014_9290_MOESM1_ESM.eps (1.1 mb)
Endocranial growth curves in absolute terms: non-human hominoids. Absolute endocranial volumes are plotted against age groups as coloured filled circles. Volume growth curves are shown as dashed lines, cubed centroid size growth curves as solid lines. (EPS 1108 kb)
11692_2014_9290_MOESM2_ESM.eps (1.6 mb)
Ontogenetic shape trajectories as ontogenetic sequences of specimens in shape space: non-human great apes. PCA of Procrustes shape variables from the eruption of deciduous dentition (age group 2) to adulthood (age group 6). A: The projection of principal components one and two; B: The projection of principal components one and three. Cumulative explained variance for the first three principal components is 64 %. Borderless convex hulls represent pooled sexes of age groups 2-6 for each species; convex hulls with dashed borders represent adult females, those with solid borders represent adult males. Age group labels denote age group means. Lines are B-spline curves of the average species-specific trajectories. Endocranial shape variation along the first three PCs is visualized as mean shapes ± two standard deviations (± 2 SDVs) from the sample mean. (EPS 1656 kb)
11692_2014_9290_MOESM3_ESM.xlsx (12 kb)
Classification accuracy of developmental simulations. (XLSX 12 kb)
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Shape change in humans along entire trajectory in fig. 5b. (MPG 2156 kb)

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Shape change in humans between age groups 2 and 3 in fig. 5b, exaggeration factor: 2. (MPG 735 kb)

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Shape change in humans between age groups 3 and 4 in fig. 5b, exaggeration factor: 2. (MPG 735 kb)

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Shape change in humans between age groups 4 and 6 in fig. 5b, exaggeration factor: 2. (MPG 730 kb)

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Shape change in chimpanzees along entire trajectory in fig. 5b. (MPG 2886 kb)

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Shape change in chimpanzees between age groups 2 and 3 in fig. 5b, exaggeration factor: 2. (MPG 737 kb)

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Shape change in chimpanzees between age groups 3 and 4 in fig. 5b, exaggeration factor: 2. (MPG 730 kb)

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Shape change in chimpanzees between age groups 4 and 5 in fig. 5b, exaggeration factor: 2. (MPG 739 kb)

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Shape change in chimpanzees between age groups 5 and 6 in fig. 5b, exaggeration factor: 2. (MPG 739 kb)

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Shape change in gorillas along entire trajectory in fig. 5b. (MPG 2889 kb)

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Shape change in gorillas between age groups 2 and 3 in fig. 5b, exaggeration factor: 2. (MPG 739 kb)

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Shape change in gorillas between age groups 3 and 4 in fig. 5b, exaggeration factor: 2. (MPG 739 kb)

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Shape change in gorillas between age groups 4 and 5 in fig. 5b, exaggeration factor: 2. (MPG 739 kb)

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Shape change in gorillas between age groups 5 and 6 in fig. 5b, exaggeration factor: 2. (MPG 739 kb)

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Shape change in orangutans along entire trajectory in fig. 5b. (MPG 2895 kb)

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Shape change in orangutans between age groups 2 and 3 in fig. 5b, exaggeration factor: 2. (MPG 737 kb)

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Shape change in orangutans between age groups 3 and 4 in fig. 5b, exaggeration factor: 2. (MPG 737 kb)

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Shape change in orangutans between age groups 4 and 5 in fig. 5b, exaggeration factor: 2. (MPG 733 kb)

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Shape change in orangutans between age groups 5 and 6 in fig. 5b, exaggeration factor: 2. (MPG 742 kb)

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Shape change in gibbons along entire trajectory in fig. 5b. (MPG 1436 kb)

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Shape change in gibbons between age groups 4 and 5 in fig. 5b, exaggeration factor: 2. (MPG 735 kb)

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Shape change in gibbons between age groups 5 and 6 in fig. 5b, exaggeration factor: 2. (MPG 737 kb)

11692_2014_9290_MOESM26_ESM.cdf (5 kb)
Ontogenetic trajectories in age-shape-size space. Trajectories are constructed as accumulations of mean differences in shape (Procrustes distance) and size (endocranial volume difference) for each age group transition. All trajectories begin at a common origin (grey sphere). Gibbons were excluded from this analysis as only those species represented from age group 2 onwards were included. Blue spheres denote humans, orange denotes gorilla, green denotes chimpanzees and red denotes orangutans. (CDF 5 kb)

Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  • Nadia Scott
    • 1
  • Simon Neubauer
    • 1
  • Jean-Jacques Hublin
    • 1
  • Philipp Gunz
    • 1
  1. 1.Department of Human EvolutionMax Planck Institute for Evolutionary AnthropologyLeipzigGermany