Neurobehavioural integrity of chimpanzee newborns: comparisons across groups and across species reveal gene–environment interaction effects

Abstract

The aims of this article are to describe the neurobehavioral integrity of chimpanzee newborns, to investigate how early experiences affect the neurobehavioral organization of chimpanzees, and to explore species differences by comparing chimpanzee newborns to a group of typically developing human newborns. Neurobehavioral integrity related to orientation, motor performance, arousal, and state regulation of 55 chimpanzee (raised in four different settings) and 42 human newborns was measured with the Neonatal Behavioral Assessment Scale (NBAS) a semi-structured 25-minute interactive assessment. Thirty-eight chimpanzees were tested every other day from birth, and analyses revealed significant developmental changes in 19 of 27 NBAS scores. The cross-group and cross-species comparisons were conducted at 2 and 30 days of age. Among the 4 chimpanzee groups, significant differences were found in 23 of 24 NBAS scores. Surprisingly, the cross-species comparisons revealed that the human group was distinct in only 1 of 25 NBAS scores (the human group had significantly less muscle tone than all the chimpanzee groups). The human group was indistinguishable from at least one of the chimpanzee groups in the remaining 24 of 25 NBAS scores. The results of this study support the conclusion that the interplay between genes and environment, rather than genes alone or environment alone, accounts for phenotypic expressions of newborn neurobehavioral integrity in hominids.

Early Socioemotional Intervention Mediates Long-Term Effects of Atypical Rearing on Structural Covariation in Gray Matter in Adult Chimpanzees

“…This study was conducted with chimpanzees raised under three different rearing conditions living in a laboratory setting. Although there are differences in everyday practice among great ape nurseries across laboratories (e.g., Bard, Brent, Lester, Worobey, & Suomi, 2011 ) and across other captive facilities (e.g., zoos), we expected that our results would generalize to chimpanzees residing in a variety of other captive facilities that included rearing protocols approximating our three conditions.…”

Systematic mapping of developmental milestones in wild chimpanzees

“…life‐history brain development hypothesis (Garwicz, Christensson, & Psouni, 2009; Harvey & Clutton‐Brock, 1985; Kaplan, Hill, Lancaster, & Hurtado, 2000)). In line with this, it has been predicted that humans develop at a slower pace than other primates (Hawkes et al., 2017; but see Bard, Brent, Lester, Worobey, & Suomi, 2011). However, it remains unclear to what extent our long developmental period is driven by underlying constraints such as brain size growth (i.e.…”

“…This evolutionary approach is an alternative to the classic psychological one. Specifically, we predict that, as life‐history theory posits a more analogous maturation scheme of brain and behaviour, due to a similar socioecology and phylogenetic proximity, developmental milestones should be reached in a similar progression in chimpanzees and humans (Bard et al., 2011). We test these predictions comparing chimpanzee data with published human data.…”

Emotional engagements predict and enhance social cognition in young chimpanzees

“…At 4, 6, 9, and 12 months of age, RC infants experienced these nurturing interactions significantly more often than ST infants (all p s <.01). Note that the engagement experiences of both nursery- and mother-raised chimpanzee infants at the Yerkes Center were distinctly different from those of wild chimpanzees (Boesch, 2012 ; van Lawick-Goodall, 1968 ), of chimpanzees raised in other biomedical laboratories (Bard, Brent, Lester, Worobey & Suomi, 2011 ; Kalcher, Franz, Crailsheim & Preuschoft, 2008 ), of sanctuary chimpanzees (Ferdowsian, Durham, Kimwele, Kranendonk, Otali, Akugizibwe, Mulcahy, Ajarova & Johnson, 2011 ), and of home-raised chimpanzees (Fouts, 1997 ; Hayes, 1951 ; Kellogg & Kellogg, 1933 ; Temerlin, 1976 ). Note that here the chimpanzee infants did not learn any artificial symbol systems.…”