Doctoral Dissertation Improvement: The Pace and Processes of Early Diversification in Sulawesi Macaques

University Of California-Davis, Davis CA

Investigators

Abstract

In this project, the researchers ask the questions, Just how old are the human races? What evolutionary processes caused the differences that are observed among human groups? It is obvious that human beings whose ancestors hail from widely separated parts of the world appear physically different in skin color, form and color of hair, eye color, shape of the eyes and nose, and other features. It has been traditional to categorize these regional forms of humanity as "races." While differences can be extreme, there is a high degree of gradation. The gradation is to be expected, given how very uniform humans are genetically compared to chimpanzees. That finding runs counter to older views which hold that the human races evolved from separate regional stocks, albeit with some interbreeding. In contrast, the Out of Africa hypothesis argues for more recent physical divergence of human populations. The hypothesis has been tested primarily with fossil, archaeological and genetic lines of evidence. This evidence generally supports a recent origin of modern humans in Africa, followed by geographic expansion and fast diversification. However, there are some ambiguities in the evidence. Some have suggested that the evidence indicates changes in population sizes, rather than a recent origin for our species. The anatomical evidence, too, seems ambiguous. While some consider that it, too, supports the Out of Africa hypothesis, others see strong evidence of multiple origins of modern humans in different parts of the world, especially in Asia as well as Africa. Tellingly, supporters of both the African-origin and multi-regional hypotheses use the same information as the bases of their arguments. In this project, the researchers will consider a new source of evidence, that gleaned from studies of nonhuman primates. This study will evaluate the Out of Africa hypothesis of rapid geographic diversification of humanity by asking whether a key prediction of the model, rapid anatomical evolution, is seen in living nonhuman primates. They will focus on a pair of primate populations from Sulawesi, Indonesia, whose date of separation (about 12,000 years ago) is well-understood geologically. The PIs also ask whether the observed differences between the populations were driven by sexual selection (such as mating preferences) on males, or on females, or by ecology, or by chance alone. The understanding produced of how, and how fast, these anatomical differences begin to emerge in newly separated populations of primates will help us evaluate the realism of several of the assumptions of the Out of Africa hypothesis. In addition to helping learn about the origin and diversification of our own species, this study will strengthen multinational collaboration among researchers, and may lead to the creation of a new protected nature reserve on Muna Island in Sulawesi, where preliminary surveys have led to the detection and mapping of what is likely to be the last remaining forest on that recently-isolated island. The study also will provide training for a graduate student.