The dental microwear of hard‐object feeding in laboratory Sapajus apella and its implications for dental microwear formation

Abstract

Objectives: This study seeks to determine if (a) consumption of hard food items or a mixture of food items leads to the formation of premolar or molar microwear in laboratory capuchin monkeys (Sapajus apella) in one feeding session and (b) rates of microwear formation are associated with the number of food items consumed.Materials and methods: Five adult male capuchins were used in two experiments, one where they were fed unshelled Brazil nuts, and the other where they were fed a mixture of food items. Dental impressions were taken before and after each feeding session. Epoxy casts made from those impressions then were used in SEM analyses of rates of microwear formation. Upper and lower premolars and molars were analyzed. Qualitative comparisons were made and Spearman's rank-order correlations used to examine the relationship between rates of microwear formation and number of Brazil nuts consumed.Results: Premolars and molars generally showed new microwear in the form of pits and scratches. However, the incidence of those features was low (0-6%). Rates of microwear formation were highest during the consumption of Brazil nuts.Discussion: Variations in the rate of microwear formation on the premolars likely reflected patterns of ingestion whereas consistency in the rate of microwear on the molars likely reflected patterns of chewing. While dental microwear formation seemed to be correlated with the number of hard objects consumed, rates did differ between individuals. Differences in results between the two experiments demonstrate some of the limitations in our knowledge of dental microwear formation.

Applying dental microwear texture analysis to the living: Challenges and prospects

“…Ultimately, most of the microwear studies listed in Table 5, except for the present work, Ungar et al (2019), and Percher et al (2018), used SEM to collect data. This approach involves the manual counting of features by a researcher, which means that one may analyze images only partially obscured by biofilm, such as the one in Figure 3c,d (Teaford et al, 2017; Teaford & Oyen, 1989a; Teaford & Oyen, 1989b), whereas the white‐light scanning microscope used in DMTA cannot cope with this hindrance (Teaford et al, 2020).…”

“…In addition, microwear researchers should consistently report on success rates in obtaining usable impressions. Even though in vivo studies might remain a small subset of DMTA, such studies would increase the resolution of the technique and allow for a true understanding of how dental microwear is produced (Teaford et al, 2020).…”

“…Finally, microwear surfaces have variable turnover rates—known as the “Last Supper Effect” (Grine, 1986)—wherein any given microwear surface captures only a snapshot in time of the food consumed by the individual, making historical characterizations of a group's diet difficult to tie in to microwear patterns. Although microwear can change after a single feeding bout (Teaford, Ungar, Taylor, Ross, & Vinyard, 2020), the amount of time required to fully change a microwear pattern will be situation specific, depending on a range of factors, such as material or mechanical properties of food items, food processing techniques, exogenous grit, and even individual chewing patterns (El Zaatari, 2010; Lucas et al, 2013; Percher et al, 2018; Schmidt, 2001; Teaford et al, 2020; Teaford & Tylenda, 1991).…”

“…To address this gap, we investigated how DMTA performs when applied to living human populations with diverse, but measurable, diets. Dental microwear studies on living primates (Nystrom, Phillips‐Conroy, & Jolly, 2004; Percher et al, 2018; Teaford et al, 2020; Teaford & Oyen, 1989a; Teaford, Ungar, Taylor, Ross, & Vinyard, 2017) and on living people (Romero, Ramírez‐Rozzi, De Juan, & Pérez‐Pérez, 2013; Teaford & Tylenda, 1991) have been carried out before using the more traditional SEM protocol. However, DMTA of a living human group has only been attempted once before by Ungar, Livengood, and Crittenden (2019), and this study focused on a single group, rather than on between‐group differences in dental microwear that could reflect diet.…”

Tooth chipping patterns inParanthropusdo not support regular hard food mastication

“…Direct evidence from enamel microwear studies of P. boisei suggests little to no hard object feeding (Ungar et al, 2008). In P. robustus , higher enamel surface complexity may indicate hard foods were consumed more frequently (Ungar, 2019; Scott et al, 2005; Peterson et al, 2018), potentially in the context of “fallback foods.” However, the role of hard plant tissues in generating microwear features is currently debated (van Casteren et al, 2020; Teaford et al, 2020). From stable carbon isotopes, the diets of P. robustus and P. boisei appear substantially different (Cerling et al, 2011; Ungar and Sponheimer, 2011).…”