The estimation and evolution of hominin body mass

Ruff, Christopher B.; Wood, Bernard

doi:10.1002/evan.21988

Cited by 6 publications

(2 citation statements)

References 122 publications

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“…Bi-iliac breadth was also measured on the living sample using the NMDID image data (Wallace et al, 2023). All measured bi-iliac breadths were converted to living bi-iliac breadths using formulae appropriate for skeletal (Ruff & Wood, 2023) and CT-derived dimensions (Ruff et al, 2018: footnote 1).…”

Section: Size Standardization Of Propertiesmentioning

confidence: 99%

The effects of the industrial transition on lower limb bone structure: A comparison of the inhabitants of Pecos Pueblo and present‐day Indigenous peoples of New Mexico

Ruff,

Wallace,

Toya

et al. 2024

American Journal of Biological Anthropology

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ObjectivesComparisons between Indigenous peoples over time and within a particular geographic region can shed light on the impact of environmental transitions on the skeleton, including relative bone strength, sexual dimorphism, and age‐related changes. Here we compare long bone structural properties of the inhabitants of the late prehistoric‐early historic Pecos Pueblo with those of present‐day Indigenous individuals from New Mexico.Materials and MethodsFemora and tibiae of 126 adults from Pecos Pueblo and 226 present‐day adults were included in the study. Cross‐sectional diaphyseal properties—areas and second moments of area—were obtained from past studies of the Pecos Pueblo skeletal sample, and from computed tomography scans of recently deceased individuals in the present‐day sample.ResultsFemora and tibiae from Pecos individuals are stronger relative to body size than those of present‐day Indigenous individuals. Present‐day individuals are taller but not wider, and this body shape difference affects cross‐sectional shape, more strongly proximally. The tibia shows anteroposterior strengthening among Pecos individuals, especially among males. Sexual dimorphism in midshaft bone shape is stronger within the Pecos Pueblo sample. With aging, Pecos individuals show more medullary expansion but also more subperiosteal expansion than present‐day individuals, maintaining bone strength despite cortical thinning.DiscussionHigher activity levels, carried out over rough terrain and throughout adult life, likely explain the relatively stronger lower limb bones of the Pecos individuals, as well as their greater subperiosteal expansion with aging. Greater sexual dimorphism in bone structure among Pecos individuals potentially reflects greater gender‐based differences in behavioral patterns.

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Section: Size Standardization Of Propertiesmentioning

confidence: 99%

The effects of the industrial transition on lower limb bone structure: A comparison of the inhabitants of Pecos Pueblo and present‐day Indigenous peoples of New Mexico

Ruff,

Wallace,

Toya

et al. 2024

American Journal of Biological Anthropology

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“…Smaller, they are not such a risk to kill. Body weight estimates for early Homo (50-90 kg) and Australopithecus (25-60 kg) [384] exceed this 20 kg threshold, and they could also complement that by dabbing themselves with the blood scent of larger prey hunted by potential predators. Consequently, their size and smell would categorise Homo as a fellow predator.…”

Section: Intolerance Vs Tolerance Cost-benefit Balancementioning

confidence: 99%

Darwin’s road not taken: white sclera, shared intentionality, niche construction, predator fear, teams and Homo origins

Skoyles

2023

Preprint

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Palaeoanthropologists have yet to pinpoint how Homo evolved from Australopithecus. I propose niche construction ending predator ambush and stalking attacks, white sclera, and ultrafast team cognition were key.Human white sclera allows the quick, distant detection of line-of-sight. This is unique. In other primates, predators eliminate conspicuous-eyed individuals. Consequently, nonhuman primates have coloured sclera, hiding gaze direction broadcasting. Recognizing line-of-sight’s split-second changes from a distance enables the ultrafast detection of attention shifts that support intercoupling cognitions (cognitive alignment, shared intentionality, and split-second coordination). Under certain conditions, such split-second coordinated teams can niche-construct predator-shunning safe habitats. Once shunning replaces hunting, it stops white sclera targeting, allowing it to persist.Constructing predator-safe habitats ended the “landscape of fear” that limited Australopithecus foraging, health, and cognitive/cultural development. Once shunned and freed from fear, these safe habitats allowed previously “wheel-clamped” cognitive potentials, including social learning, to flourish, revolutionizing hominin capacity for cultural evolution and cumulative culture. Thus, predator-safe niche construction transfigured Australopithecus’s phenotype into Homo. White-eyed australopiths, I argue, were the first humans.Significance Statement: The prevailing view is that genetic changes initiated the emergence of the human genus Homo. However, research on predator fear in songbirds and capuchin monkeys, along with its negative effects on social learning and cultural transmission, points to a non-genetic alternative. In this account, Homo arose when a group of Australopithecus found a way to gain predator shunning, not attack, freeing them from constant predation fear. Ending predator fear unlocked previously “wheel-clamped” cognitive and cultural potentials, triggering a phenotypic change dividing humans from other hominids. Critically, a plausible mechanism must have enabled Homo to achieve predator shunning to end its predation. A comprehensive review provides a compelling argument that such a mechanism did indeed exist and that its past occurrence can be empirically established. The proposed mechanism centres on two often-overlooked human traits: the conspicuous direction of our line-of-sight due to white sclera and our unique ability for split-second team coordination. The proposal posits that Homo emerged when white-sclera-eyed Australopithecus used their conspicuous line-of-sight to split-second coordinate as teams to get predators to shun them. This perspective challenges dominant genetic assumptions and identifies unexplored avenues to research human origins.

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Technical note: Prediction of body mass from stature and pelvic breadth

Ruff,

Wallace,

Abeyta‐Brown

et al. 2024

American Journal of Biological Anthropology

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Equations for predicting body mass from stature and bi‐iliac (maximum pelvic) breadth have been developed, but have had variable success when applied to living or recently deceased individuals, calling into question their general applicability. Here we test these equations on a large, ethnically diverse sample. Skeletal and anthropometric data for 507 recently deceased Indigenous, Hispanic, and non‐Hispanic White adults were obtained from the New Mexico Decedent Image Database. The body mass of individuals with a “normal” body mass index (BMI = 18.5–24.9) is very accurately predicted, with an average directional bias of about 1% and an average random error of less than 8%. Underweight individuals (BMI < 18.5) are overpredicted, while overweight (BMI = 25–29.9) and especially obese (BMI≥30) individuals are underpredicted. Within BMI categories, there is a strong and isometric relationship between predicted and true body mass. Individual body mass prediction errors using the stature/bi‐iliac method are mainly dependent on variation in BMI. Because earlier humans were more likely to fall within or close to the normal BMI range, the equations should be applicable, on an individual basis, in archeological and paleontological contexts. Because of the prevalence of obesity in many modern populations, these equations are not applicable in a general forensic context. We derive new equations from nonobese individuals in our sample (n = 338), which produce reasonable average prediction errors. If obese individuals can be identified using other skeletal parameters, these equations may be useful in estimating body mass in nonobese forensic cases.

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The estimation and evolution of hominin body mass

Cited by 6 publications

References 122 publications

The effects of the industrial transition on lower limb bone structure: A comparison of the inhabitants of Pecos Pueblo and present‐day Indigenous peoples of New Mexico

The effects of the industrial transition on lower limb bone structure: A comparison of the inhabitants of Pecos Pueblo and present‐day Indigenous peoples of New Mexico

Darwin’s road not taken: white sclera, shared intentionality, niche construction, predator fear, teams and Homo origins

Technical note: Prediction of body mass from stature and pelvic breadth

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