Chimpanzee fauna isotopes provide new interpretations of fossil ape and hominin ecologies

Abstract

Carbon and oxygen stable isotopes within modern and fossil tooth enamel record the aspects of an animal's diet and habitat use. This investigation reports the first isotopic analyses of enamel from a large chimpanzee community and associated fauna, thus providing a means of comparing fossil ape and early hominin palaeoecologies with those of a modern ape. Within Kibale National Park forest, oxygen isotopes differentiate primate niches, allowing for the first isotopic reconstructions of degree of frugivory versus folivory as well as use of arboreal versus terrestrial resources. In a comparison of modern and fossil community isotopic profiles, results indicate that Sivapithecus, a Miocene ape from Pakistan, fed in the forest canopy, as do chimpanzees, but inhabited a forest with less continuous canopy or fed more on leaves. Ardipithecus, an early hominin from Ethiopia, fed both arboreally and terrestrially in a more open habitat than inhabited by chimpanzees.

Do Oxygen Isotope Values in Collagen Reflect the Ecology and Physiology of Neotropical Mammals?

“…Oxygen isotope values track those for carbon and nitrogen insofar as they are higher for plants and animals inhabiting dry, hot habitats compared to moist, cool ones (e.g., Cormie et al, 1994;Nelson, 2013). In addition, the δ 18 O values of plants are positively related to height in stratified canopies (Sternberg et al, 1989;Ometto et al, 2005).…”

“…Additionally, nitrogen isotope values can be measured only in proteinaceous tissues (i.e., collagen and keratin), which seldom preserve beyond several thousand years (Tuross et al, 1988). Oxygen isotope (δ 18 O) values also have the potential to identify ecological differences among organisms (e.g., Bryant and Froelich, 1995;Lee-Thorp and Sponheimer, 2005;Nelson, 2013). Additionally, because oxygen is present in collagen and bioapatite, which is well preserved in the fossil record, it is well suited for investigating the foraging ecology of extant and extinct organisms.…”

“…Additionally, because oxygen is present in collagen and bioapatite, which is well preserved in the fossil record, it is well suited for investigating the foraging ecology of extant and extinct organisms. Yet few studies have investigated how variation in diet or habitat might affect oxygen isotope variation in modern or fossil communities (Bocherens et al, 1995(Bocherens et al, , 1996Kohn, 1996;Cerling et al, 2004;Lee-Thorp and Sponheimer, 2005;Levin et al, 2006;Secord et al, 2008;White et al, 2009;Pietsch et al, 2011;Moritz et al, 2012;Krigbaum et al, 2013;Nelson, 2013;Crowley, 2014;Carter and Bradbury, 2015).…”

“…These patterns are primarily driven by varying temperature, humidity, light, vapor pressure deficit, and the δ 18 O of atmospheric water vapor beneath the forest canopy (Farquhar and Sharkey, 1982;Ometto et al, 2005;Barbour et al, 2007). Given that isotopic differences in canopy and understory vegetation are transmitted to the animals that forage in these strata, it is plausible that oxygen isotopes can distinguish arboreal species from those that feed on or near the forest floor (Krigbaum et al, 2013;Nelson, 2013;Carter and Bradbury, 2015).…”

Origins of Bipedalism

“…The earliest hominins, Sahelanthropus and Ardipithecus have been suggested to have been bipedal and partly arboreal (Nelson 2013). Interestingly, extinct hominins that were close to the common chimpanzee ancestor were partially bipedal.…”