males who are now dead or disappeared, from all of whom we took samples. We now look at these
five in turn:
- Kewaya was a subadult female when we first identified and named her in 1992. She is possibly the
daughter of Nambi, currently alpha female at Sonso; if so it would seem that Nambi moved into the
Sonso community having already conceived outside it. - Mark arrived with Melissa in October 2001 at which time he was already a juvenile. Melissa was one
of three parous females who arrived together at this time and we concluded they came from a com-
munity that was disintegrating (see Chapter 5). His father would thus be expected to be outside Sonso. - Bob was first seen in 1992 at which time he was already an Infant 2 (aged 3–4 years) with his
mother Ruda. Possibly his father disappeared very early in our study, before being identified (iden-
tification began in 1992), after siring Bob. - Kato was born in late September 1993, his mother is Kutu. His paternity outside the Sonso community
may be explicable in the same way as Bob’s, i.e. his father disappeared before we had identified him. - Zalu is harder to explain. He was born to Zana at the end of July 1995. Zana has injuries to both
hands and is relatively immobile compared with other females (Munn 2003). She is rather solitary
and ranges on the outskirts of the community’s range. This might have given her an opportunity to
mate with a non-Sonso male.
MHC genetics
A second, more recent, genetic study ongoing at Sonso focuses on the genetics of the major histo-
compatibility complex (MHC) in relation to health.^104 Products of the MHC class II genes are crucial
components of the immune recognition system, presenting peptides of extracellular origin to helper
T cells. The extensive polymorphism and allelic diversity of these genes are believed to increase the
number of different peptides bound and recognized by the immune system, thus conferring a wider
repertoire of resistance to disease. For this study, we are collaborating with Dr Leslie Knapp of the
Department of Biological Anthropology at the University of Cambridge, with fieldwork by Catherine
O’Hara who has developed new techniques for the study of non-invasively collected samples and who
is currently analysing the data. The objective of this research is to build up a database of individual MHC
genotypes that may be used to investigate how the MHC influences resistance to infection, social status,
mating behaviour and parity in wild chimpanzees. At this stage of the research, individual haplotypes are
being generated and ultimately, using the MHC data, the following hypotheses will be tested:
● MHC diversity is favoured by overdominant selection with heterozygotes being more resistant to
parasitic infection;
● MHC-based disassortative mating results in more MHC heterozygote progeny than expected.
Like the Leipzig work, the Cambridge study is based on totally non-invasive methods, the DNA being
extracted from faecal samples. While difficult to achieve, these results will improve our understanding
of health and reproduction in the Sonso chimpanzees.
252 Appendices
(^104) This study is funded principally by the Leakey Foundation.