Early hominid brain evolution: a new look at old endocasts

Falk, Dean; Redmond, John C.; Guyer, John; Conroy, C.; Recheis, Wolfgang; Weber, Gerhard; Seidler, Horst

doi:10.1006/jhev.1999.0378

Cited by 148 publications

(122 citation statements)

References 30 publications

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“…3) are consistent with their typically sloping foreheads, frontal lobes that are more pointed rostrally in dorsal views, and hypothetically smaller forebrains (15,21,26,27,29). In brains of normal humans, the orbital surface of the frontal lobes (in lateral view) is expanded due to ventral protrusion of the cortex medially (underneath the paths of the olfactory tracts) (33) (Fig. 1 and SI Fig.…”

Section: Discussionsupporting

confidence: 51%

“…On the other hand, LB1's endocast shows affinities with Homo erectus in its relative height, disparity between its maximum and frontal breadths, relative widths of its caudal and ventral surfaces and long, low lateral profile (1). Its tiny cranial capacity, relative brain size, and derived ventrally expanded orbital surface, however, show affinities with Australopithecus africanus (33). Because subsets of LB1's features occur normally in other hominins and because virtual reconstruction adjusted for the slight in situ distortion of LB1's skull, these endocast features should not be attributed to pathology nor to postmortem mechanical deformation.…”

Section: Discussionmentioning

confidence: 99%

“…4). Between 2.5 and 3.0 million years ago, a derived ventrally expanded orbital surface and squared-off frontal lobes (in dorsal view) appeared in another species that may have been directly ancestral to humans, Australopithecus africanus (33). These converging data raise the interesting possibility that genes involved in primary microcephaly (e.g., ASPM) may have been important for the evolution of the shape and internal organization of the orbitofrontal cortex in addition to their effects on brain size.…”

Section: Discussionmentioning

confidence: 99%

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Brain shape in human microcephalics and Homo floresiensis

Falk

Hildebolt

Smith

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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Because the cranial capacity of LB1 (Homo floresiensis) is only 417 cm 3 , some workers propose that it represents a microcephalic Homo sapiens rather than a new species. This hypothesis is difficult to assess, however, without a clear understanding of how brain shape of microcephalics compares with that of normal humans. We compare three-dimensional computed tomographic reconstructions of the internal braincases (virtual endocasts that reproduce details of external brain morphology, including cranial capacities and shape) from a sample of 9 microcephalic humans and 10 normal humans. Discriminant and canonical analyses are used to identify two variables that classify normal and microcephalic humans with 100% success. The classification functions classify the virtual endocast from LB1 with normal humans rather than microcephalics. On the other hand, our classification functions classify a pathological H. sapiens specimen that, like LB1, represents an Ϸ3-foottall adult female and an adult Basuto microcephalic woman that is alleged to have an endocast similar to LB1's with the microcephalic humans. Although microcephaly is genetically and clinically variable, virtual endocasts from our highly heterogeneous sample share similarities in protruding and proportionately large cerebella and relatively narrow, flattened orbital surfaces compared with normal humans. These findings have relevance for hypotheses regarding the genetic substrates of hominin brain evolution and may have medical diagnostic value. Despite LB1's having brain shape features that sort it with normal humans rather than microcephalics, other shape features and its small brain size are consistent with its assignment to a separate species.virtual endocast

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Section: Discussionsupporting

confidence: 51%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Brain shape in human microcephalics and Homo floresiensis

Falk

Hildebolt

Smith

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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“…Comparative measurements of the virtual endocast with other australopithecine endocasts reveal that Taung shares a number of shape features that align it more closely with other A. africanus specimens than with Paranthropus endocasts, including squaredoff frontal lobes and the shape of the temporal poles (3,13). This finding suggests that, with a brain size that falls within the range for great apes, but represents a higher degree of encephalization, A. africanus was neurologically reorganized compared with similarly sized Paranthropus brains (13,14). It is not known, however, whether the brains of A. africanus had become reorganized in conjunction with a trend for brain enlargement, because their direct ancestors (and their brain sizes) remain unknown.…”

mentioning

confidence: 99%

Metopic suture of Taung ( Australopithecus africanus ) and its implications for hominin brain evolution

Falk

Zollikofer

Morimoto

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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The type specimen for Australopithecus africanus (Taung) includes a natural endocast that reproduces most of the external morphology of the right cerebral hemisphere and a fragment of fossilized face that articulates with the endocast. Despite the fact that Taung died between 3 and 4 y of age, the endocast reproduces a small triangular-shaped remnant of the anterior fontanelle, from which a clear metopic suture (MS) courses rostrally along the midline [Hrdlicka A (1925) Am J Phys Anthropol 8:379-392]. Here we describe and interpret this feature of Taung in light of comparative fossil and actualistic data on the timing of MS closure. In great apes, the MS normally fuses shortly after birth, such that unfused MS similar to Taung's are rare. In humans, however, MS fuses well after birth, and partially or unfused MS are frequent. In gracile fossil adult hominins that lived between ∼3.0 and 1.5 million y ago, MS are also relatively frequent, indicating that the modern human-like pattern of late MS fusion may have become adaptive during early hominin evolution. Selective pressures favoring delayed fusion might have resulted from three aspects of perinatal ontogeny: (i) the difficulty of giving birth to large-headed neonates through birth canals that were reconfigured for bipedalism (the "obstetric dilemma"), (ii) high early postnatal brain growth rates, and (iii) reorganization and expansion of the frontal neocortex. Overall, our data indicate that hominin brain evolution occurred within a complex network of fetopelvic constraints, which required modification of frontal neurocranial ossification patterns.brain size evolution | virtual endocast | fossil hominins | frontal cortex | obstetrics

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“…Oldowan technology is not complex if compared with more recent ones, but it seems to show an increased interest in relations between things: hominins had to learn the properties of different kinds of rocks; as Australopithecus africanus shows an enhancement of the brain areas related to planning (Falk et al 2000), we may suppose better anaphorics than in living non human primates. Early Acheulean brings more novelty.…”

Section: Mind Evolutionmentioning

confidence: 99%

On the Acheulean origin of mind and language

Sá-Saraiva

2012

THS

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Early hominid brain evolution: a new look at old endocasts

Cited by 148 publications

References 30 publications

Brain shape in human microcephalics and Homo floresiensis

Brain shape in human microcephalics and Homo floresiensis

Metopic suture of Taung ( Australopithecus africanus ) and its implications for hominin brain evolution

On the Acheulean origin of mind and language

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