Quantifying linear enamel hypoplasia in Virunga Mountain gorillas and other great apes

Abstract

Shallow defect morphology in mountain gorillas may have led to an underestimation of LEH prevalence in past studies. Defect depth is used as a proxy for insult severity, but depth might be influenced by inter- and intra-specific variation in enamel growth. Future studies should test whether severe insults are associated with deeper defects, as might be the case with Haloko, a wild-captured gorilla. Ongoing histologic studies incorporating associated behavioral records will test possible factors that underlie differences in defect morphology.

3D enamel profilometry reveals faster growth but similar stress severity in Neanderthal versus Homo sapiens teeth

“…The extent to which faster anterior tooth growth rates relate to other aspects of life history is yet to be fully understood, but recent evidence suggests that the tempo and mode of brain ontogeny, and possibly skeletal growth, differs between the two species 6 . Among extant apes, faster-growing species like mountain gorillas have shallower LEH defects, faster enamel growth (extension) rates, accelerated brain and somatic growth, and faster life history schedules [17][18][19]32,33 . However, more comparative data from extant and fossil hominoids are needed in order to further assess the relationships among these variables in hominins.…”

“…Researchers have long hypothesized that defect depth provides information about the severity of the stressor that disrupted growth in hominoids 16,21,27 , just as location and width of the defects tell us something about their timing and duration, respectively. Evidence from great ape studies supports this, with several wild-captured individuals exhibiting particularly deep defects that might reflect major stress events 17 . One known gorilla exhibits a defect depth of 276 µm (compared to the species median of 41 µm), and according to associated veterinary records, this defect likely formed around the time that she was captured from the wild to live in a zoo 17 .…”

“…Evidence from great ape studies supports this, with several wild-captured individuals exhibiting particularly deep defects that might reflect major stress events 17 . One known gorilla exhibits a defect depth of 276 µm (compared to the species median of 41 µm), and according to associated veterinary records, this defect likely formed around the time that she was captured from the wild to live in a zoo 17 . At the population level, mountain gorillas that developed their teeth during a period of intense human encroachment have defects that are almost twice as deep as those that lived under increased protection 17 .…”

“…One known gorilla exhibits a defect depth of 276 µm (compared to the species median of 41 µm), and according to associated veterinary records, this defect likely formed around the time that she was captured from the wild to live in a zoo 17 . At the population level, mountain gorillas that developed their teeth during a period of intense human encroachment have defects that are almost twice as deep as those that lived under increased protection 17 . Further, flanged orangutans, which exhibit higher levels of the stress hormone cortisol throughout development, have defects that are more than twice as deep as unflanged or developmentally arrested males with either the same or lower cortisol levels 28 .…”

Bioarchaeological evidence for adaptive plasticity and constraint: Exploring life‐history trade‐offs in the human past

“…For example, recent studies of LEH confirm that psychological trauma at the earliest stages of development may produce these lesions. In one instance, a gorilla with a documented life history expresses a deep LEH that is histologically estimated to the time of capture . In other instances, shortened DNA telomeres (end sequences of DNA that promote cell division by acting as disposable units during replication) are found in cases of war and social upheaval suggesting that psycho‐social experiences leave imprints on bodies that have far reaching consequences across the human life cycle .…”