Person: Worthington, Steven
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Worthington
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Steven
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Worthington, Steven
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Publication Distribution of a Chimpanzee Social Custom Is Explained by Matrilineal Relationship Rather Than Conformity(Elsevier BV, 2016) Wrangham, Richard; Koops, Kathelijne; Machanda, Zarin; Worthington, Steven; Bernard, Andrew B.; Brazeau, Nicholas F.; Donovan, Ronan; Rosen, Jeremiah; Wilke, Claudia; Otali, Emily; Muller, Martin N.High-arm grooming is a form of chimpanzee grooming in which two individuals mutually groom while each raising one arm. Palm-to-palm clasping (PPC) is a distinct style of high-arm grooming in which the grooming partners clasp each other’s raised palms. In wild communities, samples of at least 100 observed dyads grooming with raised hands showed PPC frequencies varying from <5% (M group, Mahale) to >30% dyads grooming (Kanyawara, Kibale), and in a large free-ranging sanctuary group, the frequency reached >80% dyads (group 1, Chimfunshi) [1 ; 2]. Because between-community differences in frequency of PPC apparently result from social learning, are stable across generations, and last for at least 9 years, they are thought to be cultural, but the mechanism of transmission is unknown [2]. Here, we examine factors responsible for individual variation in PPC frequency within a single wild community. We found that in the Kanyawara community (Kibale, Uganda), adults of both sexes varied widely in their PPC frequency (from <10% to >50%) and did not converge on a central group tendency. However, frequencies of PPC were highly consistent within matrilines, indicating that individuals maintained lifelong fidelity to the grooming style of their mothers. Matrilineal inheritance of socially learned behaviors has previously been reported for tool use in chimpanzees [3] and in the vocal and feeding behavior of cetaceans [4 ; 5]. Our evidence indicates that matrilineal inheritance can be sufficiently strong in nonhuman primates to account for long-term differences in community traditions.Publication News and views: Non-metric dental traits and hominin phylogeny(Elsevier BV, 2014) Carter, Katherine E.; Worthington, Steven; Smith, TanyaAnalyses of hominin dental remains conventionally include measurements of tooth crown sizes and descriptions of occlusal morphology such as minor accessory cusps, fissure patterns, and ridges (e.g., Wood, 1981, Aiello and Dean, 1990 and Bailey, 2006). Following Dahlberg, 1951 and Turner et al., 1991 developed a formal system for dividing these ‘non-metric’ aspects of dental morphology into discrete categories. This system, termed the Arizona State University Dental Anthropology System (ASUDAS), is an effective tool for discriminating among modern human populations and for assessing inter-population relationships (Scott and Turner, 1997). Other researchers later used ASUDAS to examine the evolutionary relationships of various Pleistocene hominins (Irish and Guatelli-Steinberg, 2003 and Martinón-Torres et al., 2007; but see Bailey et al., 2009). Most recently, Irish et al. (2013) used ASUDAS to assess the phylogenetic position of Australopithecus sediba, finding support for both an Au. sediba + Au. africanus clade and a clade uniting South African australopiths with Homo. However, as Kimbel (2013) has argued, there are theoretical issues with applying ASUDAS to assess phylogenetic relationships from small samples of fossil hominin dental remains. Here we explore the suitability of applying a method developed for partitioning among modern human populations to assess interspecies relationships among fossil hominins. We then discuss the ramifications of different choices made during phylogenetic estimation, including those pertaining to character weighting, clade support, and outgroup composition. We find that slight alteration of phylogenetic assumptions leads to numerous equally possible evolutionary reconstructions for Au. sediba.Publication The evolution of anthropoid molar proportions(BioMed Central, 2016) Carter, Katherine E.; Worthington, StevenBackground: Developmental processes that underpin morphological variation have become a focus of interest when attempting to interpret macroevolutionary patterns. Recently, the Dental Inhibitory Cascade (dic) model has been suggested to explain much of the variation in mammalian molar size proportions. We tested the macroevolutionary implications of this model using anthropoid primate species (n=100), focusing on overall morphological patterns, as well as predictions made about molar size variability, direct developmental control, and diet. Results: Of the species sampled, 56 % had centroids that fell within regions of molar proportion morphospace consistent with the dic model. We also found that the third molar had greater variation in size than either the first or second molars, as expected by the model. Some dic model predictions were not supported, however, such as the expected proportion of M2/M1 when the third molar is absent. Furthermore, we found that some variability in third molar size could not be explained by the influence of the inhibitory cascade. Overall, we found considerable clade-specific differences in relative molar sizes among anthropoid primates, with hominoids and cercopithecins strongly divergent from dic model predictions, and platyrrhines, colobines, and papionins more consistent with the inhibitory cascade. Finally, we investigated reasons why some clades deviated from dic model expectations. Adaptations for frugivory (e.g., bunodont cusp relief) appeared to be one driver of relatively larger second molars and have evolved independently in multiple lineages of anthropoids. Conclusions: The dic model explains some of the variation in anthropoid primate molar proportions. However, there are interesting deviations away from this broad mammalian pattern, particularly in hominoids and cercopithecins, which suggest the model is only one of multiple mechanisms determining morphological variability in mammalian teeth. Electronic supplementary material The online version of this article (doi:10.1186/s12862-016-0673-5) contains supplementary material, which is available to authorized users.Publication Built Environment and Self-Rated Health: Comparing Young, Middle-Aged, and Older People in Chengdu, China(SAGE Publications, 2021-01-05) Lyu, Yingying; Forsyth, Ann; Worthington, StevenObjectives: This article explores how the building-scale built environment is associated with self-rated health, examining differences in this association among younger, middle-aged, and older age groups. Features examined included building type, building condition, and sidewalk presence in front of dwellings. Background: Understanding how the relationships between built environments and health vary across age groups helps to build a healthy environment for all. However, most studies have concentrated on the neighborhood or indoor environment, rather than whole buildings, and few have compared age groups. Methods: This study analyzed survey data from 1,019 adults living in 40 neighborhoods in Chengdu, China, recruited through a clustered random sampling approach. It used a Bayesian logistic mixed-effects model with interaction terms between age-group indicators and other variables. Results: Significant differences exist in the relationships of self-rated health with some environmental and other indicators among age groups. For older people, living in multi-floor buildings, having a household smoker, and undertaking fewer hours of weekly exercise were associated with lower odds of reporting good, very good, or excellent health. These relationships were not identified among middle-aged and younger people. More education was associated with higher odds of reporting better health among older and middle-aged groups. Conclusions: Older people experience more health-related challenges compared to middle-aged and younger people. However, among the examined built environment factors, building type was the only significant factor related to self-rated health among older people. To promote health among older people, this study recommends adding elevators in the multi-floor buildings.Publication Response To: Chimpanzee Culture Extends Beyond Matrilineal Family Units(Elsevier BV, 2017-06) Wrangham, Richard; Worthington, Steven; Bernard, Andrew; Koops, Kathelijne; Machanda, Zarin; Muller, MartinWe thank van Leeuwen et al. for their response to our finding that matrilineal relationships strongly influence the style of high-arm grooming in wild chimpanzees of the Kanyawara community. We agree with them that grooming styles could be transmitted by different mechanisms in different contexts, and we appreciate their effort to assess whether the transmission of grooming styles within two captive groups in Chimfunshi accords with our result.