The Evolution of the Brain of Primates: Its Influence on the Form of the Skull

Hofer, H.

doi:10.1111/j.1749-6632.1969.tb20455.x

Cited by 16 publications

(5 citation statements)

References 16 publications

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“…However, this condition is linked to the effects of a dramatic posterior elongation of the occipital lobe of the telencephalon in this smallbodied, relatively large-brained platyrrhine (19,22). Anterior to its foramen magnum, the base is very long and unflexed, as in most other primates (2,23). In these cases, sufficiently close inspection of the larger anatomical context reveals the logical basis for identifying homoplasy as the most likely explanation for the observed similarity (e.g., via scaling effects of small body size in Saimiri).…”

Section: Resultsmentioning

confidence: 94%

Ardipithecus ramidus and the evolution of the human cranial base

Kimbel

Suwa

Asfaw

et al. 2014

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

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The early Pliocene African hominoid Ardipithecus ramidus was diagnosed as a having a unique phylogenetic relationship with the Australopithecus + Homo clade based on nonhoning canine teeth, a foreshortened cranial base, and postcranial characters related to facultative bipedality. However, pedal and pelvic traits indicating substantial arboreality have raised arguments that this taxon may instead be an example of parallel evolution of human-like traits among apes around the time of the chimpanzee-human split. Here we investigated the basicranial morphology of Ar. ramidus for additional clues to its phylogenetic position with reference to African apes, humans, and Australopithecus. Besides a relatively anterior foramen magnum, humans differ from apes in the lateral shift of the carotid foramina, mediolateral abbreviation of the lateral tympanic, and a shortened, trapezoidal basioccipital element. These traits reflect a relative broadening of the central basicranium, a derived condition associated with changes in tympanic shape and the extent of its contact with the petrous. Ar. ramidus shares with Australopithecus each of these human-like modifications. We used the preserved morphology of ARA-VP 1/500 to estimate the missing basicranial length, drawing on consistent proportional relationships in apes and humans. Ar. ramidus is confirmed to have a relatively short basicranium, as in Australopithecus and Homo. Reorganization of the central cranial base is among the earliest morphological markers of the Ardipithecus + Australopithecus + Homo clade.A s the confluence of the neural, locomotor, and masticatory systems, the cranial base has been the site of profound structural change in human evolution. The modern human basicranium differs from that of our closest living relatives, the great apes, in numerous aspects of shape and morphological detail (1-4). In humans, the foramen magnum and occipital condyles are more anteriorly located, the midline basicranial axis is relatively short anteroposteriorly and strongly "flexed" internally, and the bilateral structures marking vascular and neural pathways through the central part of the base are more widely separated. This organization alters the relationships between the petrous and tympanic parts of the temporal bone. These phylogenetically derived features are already seen in the earliest known skulls of Australopithecus, ca. 3.0-3.4 Ma (5, 6).The cranium of Ardipithecus ramidus, an early Pliocene (4.4 Ma) hominoid from Ethiopia, was shown to have a relatively anterior foramen magnum on a short basicranium, corroborating evidence of nonhoning canine teeth and terrestrial bipedality for phylogenetic attribution of this taxon. These sets of derived characters are shared uniquely with the Australopithecus + Homo clade (7-10). At the same time, pelvic and pedal characters indicate that Ar. ramidus also retained considerable arboreal capabilities (11)(12)(13)(14). Despite the evidence for a unique phylogenetic relationship with the Australopithecus + Homo clade, it has been a...

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Section: Resultsmentioning

confidence: 94%

Ardipithecus ramidus and the evolution of the human cranial base

Kimbel

Suwa

Asfaw

et al. 2014

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

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“…The fossils Tetonius and Necroleinur approach Tarsius in these and related features. Hofer [1969] suggested that the great breadth of the occipital plane in all three forms results from the elaboration of the occipital lobes of the visual system, which also confers an auditory advantage by in creasing interaural distance. This would aid acoustic localization by the time delay mech anism.…”

Section: Discussionmentioning

confidence: 99%

In Favor of the Necrolemur-Tarsier Hypothesis

Rosenberger¹

1985

IJFP

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The traditional view that tarsiers are more closely related to middle Tertiary European microchoerines is supported by a new examination of the gross anatomy of the basicranium. Tarsius shares with Necrolemur and Microchoerus a suite of characters spanning several subsystems of the skull: the craniofacial junction, bony proportions of the basicranium, morphology of the pterygoids and the temporomandibular joint. Comparisons with other omomyids, adapids, plesiadapiforms and modern primates suggest that the states and combinations common to Tarsius, Necrolemur and Microchoerus are derived. Fewer components can be established in Tetonius, Pseudoloris and Nannopithex, whereas only primitive tarsiiform traits are evident in Rooneyia. Functional interpretations lend confidence to the inference that these phenetically very similar traits are homologous in Tarsius and its ‘necrolemur’ allies, and demonstrate their coordination with other synapomorphies of the cranium and postcranium. Necrolemurs appear to have undergone an adaptive transition to a crepuscular life-style, relying on insects significantly, using a powerful incisal killing bite, employing specialized auditory and optical prey detection techniques, and stealthy sit-and-wait foraging habits involving an important degree of leaping locomotion. These behaviors would have been preadaptive to the biology of tarsiers, and are built upon a homologous framework of derived tarsiiform characteristics.

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“…[1][2][3][4][5][6] It has been suggested that the highly heritable brain growth rates 5,6 may not be significantly influenced by synostosis. The redirected growth patterns may result in altered brain shape but not necessarily a reduction in overall intracranial volume.…”

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confidence: 99%

Intracranial Volume Changes in Craniosynostotic Rabbits: Effects of Age and Surgical Correction

Cooper

Singhal

Barbano

et al. 2006

Plastic and Reconstructive Surgery

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These data suggest that in rabbits with uncorrected craniosynostosis, compensatory changes in the neurocranium were not capable of compensating for the loss of sutures as growth sites. The results also showed that that surgical release of the synostosed suture improved intracranial volume in the short term (25 to 42 days) but failed to change it in the long term (42 to 84 days), possibly because of rapid resynostosis of the suturectomy site. This study suggests that surgical release of the suture fusion site alone may not be adequate to allow for normal intracranial volume growth in synostotic rabbits. For this reason, it may be efficacious to design and develop adjunct protein and gene therapies to prevent resynostosis and improve postoperative intracranial volume in craniosynostotic individuals.

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The Evolution of the Brain of Primates: Its Influence on the Form of the Skull

Cited by 16 publications

References 16 publications

Ardipithecus ramidus and the evolution of the human cranial base

Ardipithecus ramidus and the evolution of the human cranial base

In Favor of the Necrolemur-Tarsier Hypothesis

Intracranial Volume Changes in Craniosynostotic Rabbits: Effects of Age and Surgical Correction

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