A climatic context for the out-of-Africa migration

Tierney, Jessica E.; deMenocal, Peter B; Zander, Paul D.

doi:10.1130/g39457.1

Cited by 133 publications

(144 citation statements)

References 32 publications

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“…The refilling of these lakes is attributed to stable precipitation conditions as eccentricity decreased (Scholz et al, 2007). The paleosol-based paleoprecipitation reconstruction indicates that Lake Victoria region remained dry until 36 ka, which is similar to the cooler and drier conditions in the Horn of Africa between 50 and 75 ka (Tierney et al, 2017) and to the record of Lake Naivasha (Trauth et al, 2003), ∼250 km to the east. Because eccentricity decreased from 70 to 36 ka, the cause for extended aridity from ∼70 to 36 ka in the Lake Victoria region must be due to factors other than eccentricity-enhanced precession.…”

Section: Discussion Paleoclimate Reconstructionmentioning

confidence: 67%

“…The mechanism for the emergence and dispersal of early modern humans is still poorly understood due to limited number of sites with coexisting fossils, artifacts, and paleoenvironmental records (McDougall et al, 2005;Brown et al, 2012;Soares et al, 2012;Rito et al, 2013). Environmental change driven by climate is a commonly suggested mechanism (Ambrose and Lorenz, 1990;Potts, 1998;Scholz et al, 2007;Blome et al, 2012;Soares et al, 2012;Rito et al, 2013;Potts and Faith, 2015;Tierney et al, 2017), but few data on African climate or environment are associated with archaeological sites prior the Last Glacial Maximum (LGM) in East Africa. This makes additional data from the Lake Victoria Basin of equatorial East Africa important especially because it directly ties pre-LGM climatic reconstructions to fossil fauna and Middle Stone Age (MSA) tools.…”

Section: Introductionmentioning

confidence: 99%

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Reconstruction of Late Pleistocene Paleoenvironments Using Bulk Geochemistry of Paleosols from the Lake Victoria Region

et al. 2017

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The impact of changing environments on the evolution and dispersal of Homo sapiens is highly debated, but few data are available from equatorial Africa. Lake Victoria is the largest freshwater lake in the tropics and is currently a biogeographic barrier between the eastern and western branches of the East African Rift. The lake has previously desiccated at ∼17 ka and again at ∼15 ka, but little is known from this region prior to the Last Glacial Maximum. The Pleistocene terrestrial deposits on the northeast coast of Lake Victoria (94-36 ka) are ideal for paleoenvironmental reconstructions where volcaniclastic deposits (tuffs), fluvial deposits, tufa, and paleosols are exposed, which can be used to reconstruct Critical Zones (CZ) of the past (paleo-CZs). The paleo-CZ is a holistic concept that reconstructs the entire landscape using geologic records of the atmosphere, hydrosphere, lithosphere, biosphere, and pedosphere (the focus of this study). New paleosol-based mean annual precipitation (MAP) proxies from Karungu, Rusinga Island, and Mfangano Island indicate an average MAP of 750 ± 108 mm year −1 (CALMAG), 800 ± 182 mm year −1 (CIA-K), and 1,010 ± 228 mm year −1 (PPM 1.0 ) with no statistical difference throughout the 11 m thick sequence. This corresponds to between 54 and 72% of modern precipitation. Tephras bracketing these paleosols have been correlated across seven sites, and sample a regional paleo-CZ across a ∼55 km transect along the eastern shoreline of the modern lake. Given the sensitivity of Lake Victoria to precipitation, it is likely that the lake was significantly smaller than modern between 94 and 36 ka. This would have removed a major barrier for the movement of fauna (including early modern humans) and provided a dispersal corridor across the equator and between the rifts. It is also consistent with the associated fossil faunal assemblage indicative of semi-arid grasslands. During the Late Pleistocene, the combined geologic and paleontological evidence suggests a seasonally dry, open grassland environment for the Lake Victoria region that is significantly drier than today, which may have facilitated human and faunal dispersals across equatorial East Africa.

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Section: Discussion Paleoclimate Reconstructionmentioning

confidence: 67%

Section: Introductionmentioning

confidence: 99%

Reconstruction of Late Pleistocene Paleoenvironments Using Bulk Geochemistry of Paleosols from the Lake Victoria Region

et al. 2017

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“…E). When compared with leaf wax data (Tierney et al ., ), the oldest peak occurs within a similar timeframe as a relatively strong northeastern African monsoon. This also occurs within the timeframe of inferred increased monsoon intensity from 40 to 50 ka.…”

Section: Travertine Formation At Regional Scalesmentioning

confidence: 97%

“…(), RC09‐166 core is from Tierney et al . (), Hölloch Cave is from Wurth et al . (), Villars Cave is from Genty et al .…”

Section: Travertine Formation On a Global Scalementioning

confidence: 99%

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Global travertine deposition modulated by oscillations in climate

Ricketts

Wagler

et al. 2019

J Quaternary Science

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Travertine deposits are important records of past fluid flow in the Earth's crust, and document fluid migration through both tectonic activity and changes in climate. While many studies hint at possible relationships between travertine formation and global climate, none have investigated these connections on a global scale. Here we compile 1649 published travertine ages from six continents to test the hypothesis that global and/or regional changes in climate regulate travertine deposition. Peaks in bedded travertine ages occur with main frequencies that correspond to 100‐kyr changes in global climate, where most peaks occur during glacial terminations or interglacial periods, including a large peak that coincides with the Early Holocene climatic optimum. Time–series analysis also suggests a possible connection with 41‐kyr obliquity cycles. At regional scales, many peaks also correspond with local times of high precipitation or wet conditions. This can be attributed to higher groundwater recharge rates, providing the necessary water to form travertine. Many bedded travertine‐depositing systems may therefore be water‐limiting and sufficient CO2 may be present even during times of no travertine deposition. Exceptions to this conclusion are banded vein travertine deposits, which typically form during times of dry climate when water tables are low. Copyright © 2019 John Wiley & Sons, Ltd.

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Hyperandrogenism associated with polycystic ovary syndrome may have a protective effect against fracture risk in female athletes: A pilot study

Manthey,

Cepon‐Robins,

Warrener

2024

American J Hum Biol

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ObjectivesPolycystic ovary syndrome (PCOS), characterized by polycystic ovaries, anovulation, and hyperandrogenism, is believed to be an evolutionary mismatch disease. Past research has examined PCOS as a uniform disease, despite variation in phenotypes across diagnostic categories, but establishing an evolutionary mismatch requires a focus on individual traits. We suggest PCOS hyperandrogenism may have been beneficial in ancestral environments because it reduced fracture risk and associated morbidity and mortality due to increased bone mineral density (BMD). We test this hypothesis by assessing fracture frequency, a proxy for BMD, in highly active females with and without PCOS hyperandrogenism.MethodsSixty‐seven reproductive‐aged women were surveyed and grouped as: high intensity interval training (HIIT; a proxy for metabolic and physical stress) athletes with hyperandrogenic PCOS (31.24%), HIIT athletes without PCOS (29.85%), and nonathletes with hyperandrogenic PCOS (38.81%). Fracture occurrence was compared between the groups using independent samples Kruskal–Wallis tests for non‐normally distributed data, and multiple regression analysis was used to examine anthropometrics, lifestyle and reproductive factors, PCOS status, and exercise frequency on fracture occurrence.ResultsFracture occurrence was higher in non‐PCOS athletes (3.8 ± 4.3) than PCOS‐athletes (1.2 ± 1.4, p = .11) and PCOS‐non‐athletes (1.0 ± 1.4, p < .01). PCOS‐athletes and nonathletes did not differ significantly in fracture occurrence (p = .33). These results were independent of factors associated with bone health.ConclusionsThese preliminary findings suggest females with PCOS‐related hyperandrogenism may be less likely to experience bone fractures and provide an initial step to explaining why PCOS has persisted despite marked negative reproductive consequences in modern populations.

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A climatic context for the out-of-Africa migration

Cited by 133 publications

References 32 publications

Reconstruction of Late Pleistocene Paleoenvironments Using Bulk Geochemistry of Paleosols from the Lake Victoria Region

Reconstruction of Late Pleistocene Paleoenvironments Using Bulk Geochemistry of Paleosols from the Lake Victoria Region

Global travertine deposition modulated by oscillations in climate

Hyperandrogenism associated with polycystic ovary syndrome may have a protective effect against fracture risk in female athletes: A pilot study

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