Early Brain Growth Cessation in Wild Virunga Mountain Gorillas (Gorilla beringei beringei)

Abstract

Understanding the life history correlates of ontogenetic differences in hominoid brain growth requires information from multiple species. At present, however, data on how brain size changes over the course of development are only available from chimpanzees and modern humans. In this study, we examined brain growth in wild Virunga mountain gorillas using data derived from necropsy reports (N = 34) and endocranial volume (EV) measurements (N = 86). The youngest individual in our sample was a 10-day-old neonatal male with a brain mass of 208 g, representing 42% of the adult male average. Our results demonstrate that Virunga mountain gorillas reach maximum adult-like brain mass by 3-4 years of age; adult-sized EV is reached by the time the first permanent molars emerge. This is in contrast to the pattern observed in chimpanzees, which despite their smaller absolute brain size, reportedly attain adult brain mass approximately 1 year later than Virunga mountain gorillas. Our findings demonstrate that brain growth is completed early in Virunga mountain gorillas compared to other great apes studied thus far, in a manner that appears to be linked with other life history characteristics of this population.

A neonatal perspective on Homo erectus brain growth

“…Age at death is known for all individuals in the extant sample. In addition, the human (Coqueugniot and Hublin, 2012) and gorilla (McFarlin et al, 2013) samples are from single populations, thus reducing potential population effects. Chimpanzee data are from the Taï Forest and the Yerkes National Primate Research Center (Herndon et al, 1999;DeSilva and Lesnik, 2006).…”

Age‐related changes in molar topography and shearing crest length in a wild population of mountain Gorillas from Volcanoes National Park, Rwanda

“…Our sample consisted of maxillary first molars (M 1 s; n 5 15: 8 females and 7 males, from individuals aged 3.7-38.0 years), maxillary second molars (M 2 s; n 5 13: 9 females and 4 males, from individuals aged 8.6-43.0 years), and maxillary third molars (M 3 s; n 5 11: 7 females and 4 males, from individuals aged 10.6-43.0 years) from a cross-sectional ontogenetic series of 18 known-age mountain gorilla skeletons. These mountain gorilla skeletons are part of a growing collection under the ownership authority of the Rwanda Development Board's Department of Tourism and Conservation and curated by the Mountain Gorilla Skeletal Project, in partnership with the Dian Fossey Gorilla Fund International, Mountain Gorilla Veterinary Project, and other Rwandan and US institutions (McFarlin et al, 2009(McFarlin et al, , 2013. Of the 18 individuals included in our known-age sample, 11 had birth and death dates known to the day, three had birth and death dates known to the month, and four were first observed as pre-reproductive individuals.…”

“…These four latter individuals have an age error of 1.5 years (i.e., 6 1.5 years). Age determination for the skeletons is described in further detail in McFarlin et al (2013) and Galbany et al (2016).…”

Synaptogenesis and development of pyramidal neuron dendritic morphology in the chimpanzee neocortex resembles humans

“…Because culture plays a fundamental role in the human adaptive complex (1), the comparative examination of neural development is important to understand the origins of human sociocognitive specializations. Compared with other primates, in humans a relatively large proportion of brain size growth takes place postnatally, allowing for social and environmental factors to powerfully impact the establishment of neural connectivity (2)(3)(4)(5)(6). Whereas macaque monkeys, the primate species that has been studied most extensively as a comparative model of neurodevelopment, are born with brains that are already ∼70% of adult mass and neonatal brain mass in great apes ranges from 36% to 56% of adult size (5, 7), in humans only ∼25% of adult mass is achieved at birth (8).…”