The
            <i>Ardipithecus ramidus</i>
            Skull and Its Implications for Hominid Origins

Suwa, Gen; Asfaw, Berhane; Kono, Reiko T.; Kubo, Daisuke; Lovejoy, C. Owen; White, Tim D.

doi:10.1126/science.1175825

Cited by 122 publications

(89 citation statements)

References 46 publications

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“…ramidus cranium presents a strong contrast with the primitive anatomy of other parts of the skull, including some of the more peripheral parts of the base, such as the glenoid region of the temporal bone, with its flat mandibular fossa and small-caliber tympanic tube (7,10). A similar distinction in phylogenetic signal is seen in the earliest known Australopithecus crania.…”

Section: Resultsmentioning

confidence: 87%

“…Within and among species of Australopithecus and early Homo there is considerable variation in the bony morphology of the nuchal and glenoid regions, including differences between "robust" and "nonrobust" species of Australopithecus (3, 5). However, this variation appears to be unlinked to the morphology of the central basicranium, the derived configuration of which, as described here, was apparently fixed early in the clade's evolutionary history (3,6,10,(24)(25)(26).…”

Section: Resultsmentioning

confidence: 99%

“…These sets of derived characters are shared uniquely with the Australopithecus + Homo clade (7)(8)(9)(10). At the same time, pelvic and pedal characters indicate that Ar.…”

mentioning

confidence: 84%

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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: 87%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

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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“…Importantly, these measures of ER capabilities index different parts of human athletic performance (speed/energy costs versus stability), supporting the idea that athletic ability in general is tied to neurobiological evolution. Although more work is clearly needed to test our hypothesis, this analysis of fossil data serves as important preliminary support for the idea that human aerobic activity [85], EQ for P. paniscus from species means of Isler et al [86]). Anterior and posterior semicircular canal radii (ASC and PSC, respectively) from Spoor et al [82] (ASC and PSC for H. neanderthalensis from Spoor et al [88]).…”

Section: Human Evolutionmentioning

confidence: 93%

Linking brains and brawn: exercise and the evolution of human neurobiology

2013

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The hunting and gathering lifestyle adopted by human ancestors around 2 Ma required a large increase in aerobic activity. High levels of physical activity altered the shape of the human body, enabling access to new food resources (e.g. animal protein) in a changing environment. Recent experimental work provides strong evidence that both acute bouts of exercise and long-term exercise training increase the size of brain components and improve cognitive performance in humans and other taxa. However, to date, researchers have not explored the possibility that the increases in aerobic capacity and physical activity that occurred during human evolution directly influenced the human brain. Here, we hypothesize that proximate mechanisms linking physical activity and neurobiology in living species may help to explain changes in brain size and cognitive function during human evolution. We review evidence that selection acting on endurance increased baseline neurotrophin and growth factor signalling (compounds responsible for both brain growth and for metabolic regulation during exercise) in some mammals, which in turn led to increased overall brain growth and development. This hypothesis suggests that a significant portion of human neurobiology evolved due to selection acting on features unrelated to cognitive performance.

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“…Ponce de León and Zollikofer, 1999). Recently discovered crania of the early hominids Sahelanthropus tchadensis and Ardipithecus ramidus have also been digitally restored (Zollikofer et al, 2005;Suwa et al, 2009). The importance of digital restoration is growing.…”

Section: Introductionmentioning

confidence: 99%

Computerized assembly of neurocranial fragments based on surface extrapolation

Kikuchi

Ogihara

2013

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Fossil crania are often fractured and fragmented due to compaction and diagenesis. To restore the antemortem appearance of a fossil cranium, it is necessary to correctly assemble the fragments into their original anatomical positions. In this study, we propose a concept for computerized reconstruction that employs surface extrapolation to aid the assembly of fossil neurocranial fragments. Specifically, we approximate the surface of each neurocranial fragment using a bicubic Bézier surface to extrapolate the surface and mathematically predict the shape of adjacent fragments. The positions and orientations of adjacent fragments were calculated by minimizing the fitting errors. To evaluate the usefulness of this concept, we virtually divided modern human and chimpanzee neurocrania into pieces and used the proposed method to reassemble the generated virtual fragments. The neurocranial fragments were smoothly and correctly assembled. Comparison of the results obtained using the proposed method and conventional manual assembly revealed that the proposed method delivered similar performance in terms of differences between the original and reassembled shapes. However, the accuracy of the reassembly was found to be worse in the chimpanzee case because the fragments were more curved than those for the human cranium. Although there are some methodological limitations, the proposed concept may be useful for development of digital reassembly of fossil neurocranial fragments.

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The Ardipithecus ramidus Skull and Its Implications for Hominid Origins

Cited by 122 publications

References 46 publications

Ardipithecus ramidus and the evolution of the human cranial base

Ardipithecus ramidus and the evolution of the human cranial base

Linking brains and brawn: exercise and the evolution of human neurobiology

Computerized assembly of neurocranial fragments based on surface extrapolation

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