A model of the biogeographical journey from<Emphasis Type="Italic"> Proto-pan</Emphasis> to<Emphasis Type="Italic"> Pan paniscus</Emphasis>

Pan paniscus is unique in the group of African apes because of its range south of the Congo River. Examination of the bio-geographical journey of the genus Pan to the species P. paniscus is important when discussing the evolution of African apes. This paper is a review of the paleo-geographic events, the zoogeography, and faunal sorting which influenced P. paniscus divergence from the Proto-pan ancestor within the recent Miocene through Pliocene Epochs, approximately 10–2 MYA. Finally, by elucidating modern day evidence of food plant forms in the southern periphery exploited by P. paniscus in the forest/savanna mosaic habitat, we are able to conclude with those extrinsic events that most influenced the occurrence and distribution of P. paniscus. Electronic Publication     

Frequencies of complex diseases in hybrid populations

Diseases of complex etiology demonstrate considerable variation in their frequencies in different ethnic populations. Noninsulin-dependent diabetes mellitus (NIDDM), rheumatoid arthritis, and several cardiovascular diseases constitute examples of such disorders. In genetic studies involving hybrid populations of known ancestry, it is of interest to compare and correlate disease prevalence with the admixture proportion, the latter estimated from a number of polymorphic genetic markers. Theoretical formulations are provided relating disease prevalence in a hybrid population to the admixture proportion under different models of disease transmission. It is shown that the relationship between admixture proportion and disease frequency provides discriminatory power regarding the mode of inheritance. This method is illustrated with an example comparing the proportion of Amerindian ancestry in Mexican-Americans and the prevalence of NIDDM. It is found that genetic factors are involved in susceptibility to NIDDM, but the mode of inheritance cannot be explained by any simple genetic model, and the role of sporadic events cannot be totally ruled out.     

Comparative locomotor behavior of chimpanzees and bonobos: The influence of morphology on locomotion

Results from a 10 month study of adult male and female bonobos (Pan paniscus) in the Lomako Forest, Zaire, and those from a 7 month study of adult male and female chimpanzees in the Tai Forest, Ivory Coast (Pan troglodytes verus), were compared in order to determine whether there are species differences in locomotor behavior and substrate use and, if so, whether these differences support predictions made on the basis of interspecific morphological differences. Results indicate that bonobos are more arboreal than chimpanzees and that male bonobos are more suspensory than their chimpanzee counterpart. This would be predicted on the basis of male bonobo's longer and more narrow scapula. This particular finding is contrary to the prediction that the bonobo is a “scaled reduced version of a chimpanzee” with little or no positional behavior difference as had been suggested. This study provides the behavioral data necessary to untangle contradictory interpretations of the morphological differences between chimpanzees and bonobos, and raises a previously discussed (Fleagle: Size and Scaling in Primate Biology, pp. 1–19, 1985) but frequently overlooked point–that isometry in allometric studies does not necessarily equate with behavioral equivalence. Several researchers have demonstrated that bonobos and chimpanzees follow the same scaling trends for many features, and are in some sense functionally equivalent, since they manage to feed and reproduce. However, as reflected in their morphologies, they do so through different types and frequencies of locomotor behaviors. © 1993 Wiley-Liss, Inc.     

The evolutionary history of human and chimpanzee Y-chromosome gene loss

Recent studies have suggested that gene gain and loss may contribute significantly to the divergence between humans and chimpanzees. Initial comparisons of the human and chimpanzee Y-chromosomes indicate that chimpanzees have a disproportionate loss of Y-chromosome genes, which may have implications for the adaptive evolution of sex-specific as well as reproductive traits, especially because one of the genes lost in chimpanzees is critically involved in spermatogenesis in humans. Here we have characterized Y-chromosome sequences in gorilla, bonobo, and several chimpanzee subspecies for 7 chimpanzee gene-disruptive mutations. Our analyses show that 6 of these gene-disruptive mutations predate chimpanzee-bonobo divergence at approximately 1.8 MYA, which indicates significant Y-chromosome change in the chimpanzee lineage relatively early in the evolutionary divergence of humans and chimpanzees.     

Pan paniscus and human evolution

Detailed comparisons of the postcranium, cranium, and dentition of Pan paniscus, Pan troglodytes, and Homo reveal that except for slight differences in fore- and hindlimb proportions and the morphology of the shoulder, the postcranium of the two species of Pan are allometrically scaled variants of the same animal and one does not resemble Homo more than the other. Nor does the postcranium of one species of Pan resemble Australopithecus more closely than the other when the effects of body size are controlled. The over all morphological pattern of the skull and teeth of the two chimpanzees is clearly different, however, but both are about equally distinct from the earliest known members of the family Hominidae.     

A brief note on the effects of novel enrichment on an unwanted behaviour of captive bonobos

Animals in captivity may show undesirable behaviour when they are not sufficiently challenged, making it essential for their well-being to provide daily enrichment to zoo animals. Primates need a regular replacement with novel enrichment objects to prevent them from getting bored and look for challenging situations which might be even more undesirable. A socially housed group of bonobos showed behavioural problems such as stealing and rough handling and playing with a newborn infant in the group. To study whether providing novel environmental enrichment has an effect on this phenomenon we performed an experiment where we observed the change in behaviour in the presence of familiar and novel enrichment devices. When provided with novel enrichments, the general activity of the group increased. Simultaneously, these novel behavioural challenges significantly decreased the frequency of taking the newborn infant from its mother. Our results confirm previous findings that continuous application of new enrichments is necessary for providing sensory stimulation to primates as it promotes their well-being and indirectly might influence breeding success as well.     

Locomotor behavior of Pan paniscus in Zaire

The locomotor behavior of Pan paniscus was studied over a four-week period in Equateur, Republic of Zaire. Bonobos were found to be both arboreal and terrestrial in their daily activities. In the trees adult bonobos are basically quadrupedal, but they also have significant components of armswinging, diving, leaping, and bipedalism in their locomotor repertoire.     

Social games between bonobos and humans: evidence for shared intentionality?

Triadic social games are interesting from a cognitive perspective because they require a high degree of mutual social awareness. They consist of two agents incorporating an object in turn-taking sequences and require individuals to coordinate their attention to the task, the object, and to one another. Social games are observed commonly in domesticated dogs interacting with humans, but they have received only little empirical attention in nonhuman primates. Here, we report observations of bonobos (Pan paniscus) engaging in social games with a human playmate. Our behavioral analyses revealed that the bonobos behaved in many ways similar to human children during these games. They were interested in the joint activity, rather than the play objects themselves, and used communicative gestures to encourage reluctant partners to perform their role, suggesting rudimentary understanding of others' intentions. Our observations thus may imply that shared intentionality, the ability to understand and shares intention with other individuals, has emerged in the primate lineage before the origins of hominids.