Prevalence and Etiology of Linear Enamel Hypoplasia in Monkeys and Apes from Asia and Africa

Abstract

Ninety-seven specimens of sympatric monkeys and apes from East Malaysia and 115 monkeys and apes from West Africa are examined in order to evaluate the magnitude and nature of the great ape-monkey linear enamel hypoplasia (LEH) ‘dichotomy’. This study demonstrates that great apes from both regions have a higher incidence of LEH and repetitive LEH than do gibbons and monkeys. However, the authors find that the dichotomy is not as clear-cut as previous research suggests, since some monkey samples exhibit high LEH frequencies. The authors evaluate the potential influence of great ape-monkey differences in crown height on this dichotomy. They show that canine crown height variation is weakly associated with LEH variation. Differences between monkeys and great apes in their crown formation spans and in their experience of environmental stress may be more likely causes of the dichotomy.

Hypothesis for the causes and periodicity of repetitive linear enamel hypoplasia in large, wild African (Pan troglodytes and Gorilla gorilla) and Asian (Pongo pygmaeus) apes

“…This marked advantage is offset, of course, by the nonspecificity of enamel hypoplasia, i.e., enamel reacts in a generalized fashion to different stressors. Nevertheless, it is clear that both African and Asian large apes commonly show rLEH, a pattern which is so widespread (Guatelli-Steinberg and Skinner, 2000) that we feel a common cause can be found. One important step is to compare periodicity of cyclic stress among apes from the two land masses, as we have done here.…”

“…The African sample is composed of sympatric common chimpanzees (Pan troglodytes) and western lowland gorillas (Gorilla gorilla) from West Africa, and particularly Cameroon, collected mostly in the 1930s. Details of this sample may be found in Skinner (1986) and Guatelli-Steinberg and Skinner (2000). For the purposes of this study, orangutans are ascribed to a single species Pongo pygmaeus with Bornean and Sumatran subspecies.…”

“…We recently examined this difference. It is clear that crown formation span is the primary, but not sole, factor in the marked preponderance of affected apes (Guatelli-Steinberg and Skinner, 2000). The slow maturation of contemporary apes results in their often showing repetitive episodes of linear enamel hypoplasia (rLEH); moreover, the visual and mathematical impression of the interval between adjacent episodes strongly suggests a regular cyclic stressor (Skinner, 1986;Skinner et al, 1995) whose periodicity is unknown.…”

Enamel hypoplasia in the deciduous teeth of great apes: Variation in prevalence and timing of defects

“…Both species were obtained from the same areas, and specimen locations were recorded with varying levels of precision (usually latitude and longitude recorded within 5 min). These details lead to the conclusion that numerous social groups were sampled from a limited area, justifying the assertion of biotic sympatry (for location map and details, see Skinner, 1986a;Guatelli-Steinberg and Skinner, 2000). While general features of the region from which specimens were collected are known (rainfall, 1,500 mm/year; altitude, up to 2,500 feet above mean sea level), habitat (evergreen rainforest) details of feeding behavior, and microhabitat utilization remain unknown.…”

Biological spacetime and the temporal integration of functional modules: A case study of dento–gnathic developmental timing

“…In addition to genetic variation, primate odontogenesis is subject to environmental effects including physiological stresses due to fetal and childhood disease and poor nutrition as well as food toughness, that manifest phenotypically in the structural composition of tooth tissues (Sarnat and Schour, 1941;Kreshover, 1944;Guatelli-Steinberg, 1998, tooth size (Townsend and Brown, 1978;Townsend, 1980;Dempsey and Townsend, 2001), and occlusion differences (Corruccini et al, 1990). Under-standing the factors that regulate or affect ontogenetic schedules, for example, epithelial-mesenchymal interactions and sources of temporal instructions, will better equip workers to distinguish variables that significantly affect or drive evolutionary changes in the dentition.…”