- Award ID(s):
- 2020044
- NSF-PAR ID:
- 10432592
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Date Published:
- Journal Name:
- Science
- Volume:
- 380
- Issue:
- 6641
- ISSN:
- 0036-8075
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Tectonically driven physiographic evolution has profound effects on the climate and vegetation of Early Miocene terrestrial ecosystems across eastern Africa, creating habitat heterogeneity. Early hominoids were present on these dynamic landscapes, which likely influenced their evolutionary history. In western Kenya, a series of Early Miocene (ca.19-21Ma) fossiliferous exposures around the now-extinct Tinderet volcano document this history through preservation of hominoid fossils, fossil leaves, tree stump casts, and paleosols. Here, we use multiple proxies to reconstruct the paleoclimate and paleoecology of the fossil site Koru-16. Sedimentological and stratigraphic analysis indicate the landscape was disturbed by periodic eruptions of the volcano followed by intervals of stability, as shown by features of moderate to poorly developed paleosols. Paleoclimate estimates using the paleosol-paleoclimate model (PPM) indicate warm and wet climate conditions. Over 1000 fossil leaves were collected from two stratigraphic intervals. Seventeen morphotypes were identified across both sites, with an unequal distribution of morphotypes. Average leaf size estimate is mesophyll to megaphyll, with mean annual precipitation estimates using leaf physiognomic methods indicate >2000mm/yr. Leaf lifespan reconstructions based on leaf mass per area (MA) proxy indicate the site was predominately evergreen, with few deciduous taxa, with a MA distribution like modern tropical rainforests and tropical seasonal forests in equatorial Africa. Forest density estimates based on fossil tree stump casts indicate an open forest, with density similar to modern tropical forests that support large-bodied primates. Importantly, fossil leaves, tree stump casts, a medium-sized pythonid, a large-bodied hominoid and Proconsul africanus are all found within the same strata, indicating that these early apes lived within the reconstructed Koru-16 ecosystem. Our multi-proxy paleoclimate and paleoecological reconstructions indicate Koru-16 site sampled a very wet and warm climate that supported a tropical seasonal forest to rainforest biome. This likely provided an ideal habitat for hominoids and suggests that forested habitats played a role in the evolution of Early Miocene hominoids.more » « less
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null (Ed.)The fossil record of ‘lesser apes’ (i.e. hylobatids = gibbons and siamangs) is virtually non-existent before the latest Miocene of East Asia. However, molecular data strongly and consistently suggest that hylobatids should be present by approximately 20 Ma; thus, there are large temporal, geographical, and morphological gaps between early fossil apes in Africa and the earliest fossil hylobatids in China. Here, we describe a new approximately 12.5–13.8 Ma fossil ape from the Lower Siwaliks of Ramnagar, India, that fills in these long-standing gaps with implications for hylobatid origins. This ape represents the first new hominoid species discovered at Ramnagar in nearly a century, the first new Siwalik ape taxon in more than 30 years, and likely extends the hylobatid fossil record by approximately 5 Myr, providing a minimum age for hylobatid dispersal coeval to that of great apes. The presence of crown hylobatid molar features in the new species indicates an adaptive shift to a more frugivorous diet during the Middle Miocene, consistent with other proposed adaptations to frugivory (e.g. uricase gene silencing) during this time period as well.more » « less
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Abstract Objectives Riparian or gallery forests are critical habitats for numerous plants and animals today. Paleoanthropologically, reliance on such habitats informs behavioral and ecological reconstructions; for example, gallery forest habitats likely played a critical role in the transition from ape to hominin in the early Pliocene and may represent a preferred habitat for the last common ancestor of chimpanzees and humans. Direct indicators for gallery forest habitats preference are lacking. The objective of this article is to assess whether strontium isotope ratios are a reliable indicator of habitat preference for fauna living in and around gallery forests.
Materials and methods We report bioavailable strontium isotope ratios from the Mugiri River, its tributaries, and its gallery forest (Toro‐Semliki Wildlife Reserve, southwestern Uganda), and compare them to surrounding savanna‐grassland values. We compare these environmental values to strontium isotopes ratios in faunal tooth enamel to determine if habitat preferences are accurately reflected.
Results Gallery forest and savanna‐grassland vegetations have significantly different strontium isotope ratio profiles. We trace these isotopic differences to the influence of the Mugiri tributaries, which originate on Paleoproterozoic gneiss deposits on top of the surrounding escarpments. These isotopic differences in vegetation are mirrored in the tissues of fauna with habitat preferences for either the gallery forest or the surrounding grasslands.
Discussion This research demonstrates the potential of strontium isotope ratios to identify habitat preferences in modern or fossil fauna under proper geologic variability. It provides a methodological model for future studies seeking to reconstruct habitat preferences in early hominins.
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Abstract Objectives Availability of fruit is an important factor influencing variation in great ape foraging strategies and activity patterns. This study aims to quantify how frugivory influences activity budgets across age‐sex classes of mountain gorillas in Bwindi Impenetrable National Park, Uganda.
Materials and methods Daily proportions of fruit‐feeding and activity budgets were calculated using 6 years of observational data on four habituated groups. We fitted generalized linear mixed models to test for age‐sex differences in the amount of fruit‐feeding, and to test whether these factors influence the proportion of time spent feeding, resting, and traveling.
Results Bwindi mountain gorillas spent on average 15% of feeding time consuming fruit, with monthly variation ranging from 0 to 70%. Greater amounts of fruit‐feeding were associated with more time feeding and traveling, and less time resting. Immatures tended to spend more feeding time on fruit than adults, but less overall time feeding and more time traveling. There were no significant differences in the amount of fruit‐feeding and overall feeding time between adult females and silverback males, despite differences in body size.
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Abstract Objectives Gorillas, along with chimpanzees and bonobos, are ubiquitously described as ‘knuckle‐walkers.’ Consequently, knuckle‐walking (KW) has been featured pre‐eminently in hypotheses of the pre‐bipedal locomotor behavior of hominins and in the evolution of locomotor behavior in apes. However, anecdotal and behavioral accounts suggest that mountain gorillas may utilize a more complex repertoire of hand postures, which could alter current interpretations of African ape locomotion and its role in the emergence of human bipedalism. Here we documented hand postures during terrestrial locomotion in wild mountain gorillas to investigate the frequency with which KW and other hand postures are utilized in the wild.
Materials and methods Multiple high‐speed cameras were used to record bouts of terrestrial locomotion of 77 habituated mountain gorillas at Bwindi Impenetrable National Park (Uganda) and Volcanoes National Park (Rwanda).
Results We captured high‐speed video of hand contacts in 8% of the world's population of mountain gorillas. Our results reveal that nearly 40% of these gorillas used “non‐KW” hand postures, and these hand postures constituted 15% of all hand contacts. Some of these “non‐KW” hand postures have never been documented in gorillas, yet match hand postures previously identified in orangutans.
Discussion These results highlight a previously unrecognized level of hand postural diversity in gorillas, and perhaps great apes generally. Although present at lower frequencies than KW, we suggest that the possession of multiple, versatile hand postures present in wild mountain gorillas may represent a shared feature of the African ape and human clade (or even great ape clade) rather than KW
per se .