IS THE CHIMPANZEE A PRACTICAL MODEL OF HUMAN AGING?





J.G. Herndon,* and J. Tigges

Yerkes Regional Primate Research Center, Emory University, Atlanta GA 30322




The practicality of chimpanzees as subjects for biological and psychological research is hampered by the difficulty and expense of working with these large primates. Further, the wide range of their developmental, medical, and experimental histories can cloud interpretation of findings. Nevertheless, because of their unique biological and psychological resemblance to Homo sapiens, chimpanzees continue to be a focus of research interest. The history of research on chimpanzees has yielded valuable lifetime records of health and experimental data. Such birth-to-death records are rarely available for human populations. Two of our recent studies utilize birth-to-death records to provide insight into the biology of our nearest animal relative.

In one of these studies, we examined hematologic and blood biochemical markers across the lifespan of chimpanzees, performing both cross-sectional and longitudinal analyses of data collected from of 146 female and 106 male chimpanzees over a 9-year period. We calculated normative cross-sectional values of 14 commonly measured hematological and 20 blood chemistry variables. We also performed a longitudinal analysis of the analytes in chimpanzees by calculating the slopes and intercepts of the best-fitting trend line for each individual. The resulting slopes were analyzed by sex and by decade of age of the subjects to determine if trends were consistent. Consistent trends detected in the longitudinal analysis were usually restricted to the first decade of life, and thus represented maturational processes. The overall lack of within-animal trends covering all or most of the period from early adulthood through old age in this 9-year study suggests that a longer period of follow-up than employed here may be required to document any senescence-related changes.

In another study, we examined records of brain weights from 76 chimpanzees ranging in age from birth to 59.4 years of age. Our analysis revealed a significant sex difference, comparable in magnitude to that seen in rhesus monkeys and humans (p<0.01). When the effect of sex on brain weight was statistically controlled for, the loss of brain weight with age was 0.9 g/year (p=0.07). While this result was suggestive of a small decline in brain weight, further studies are needed to determine whether this pattern is reliable.

These two studies underscore the relevance of the chimpanzee model in age-related research. While studies with chimpanzees remain logistically challenging, the increased availability of older apes may provide the opportunity for further studies that address age-related changes, including those in the chimpanzee's complex cognitive capacities.



Key words: great apes, brain size, hematology, blood chemistry







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