Geissmann T., 1986: Twinning frequency in catarrhine primates. Primate Report 14: 100-101 (Abstract only).

Twinning frequency in catarrhine primates

T. Geissmann

Anthropological Institute, University Zürich-Irchel

It has been repeatedly suggested that twinning frequency in most catarrhine primates is approximately the same as in man, whereas the frequency in the chimpanzee and the gorilla might be higher. This study presents a re-evaluation of the evidence from the pertinent literature. It can be demonstrated that most data on twinning frequency in Old World monkeys and apes should not be used because of their small sample size. A lower limit of 1500 pregnancies is suggested here. If all frequency estimates gained from smaller samples are rejected, only four estimates for Macaca mulatta and Papio hamadryas remain. The estimates range from 0.19 to 0.35% and are in fact lower than the frequencies of most (not necessarily all) human populations. The published birth samples for apes are, however, relatively small, and the resulting twinning rates may not be reliable.