INTRODUCTION

Human offspring become independent relatively late in life and fitness in our species is therefore critically linked to the amount and quality of the parental care that children receive. This explains, in evolutionary terms, why humans generally have a resource-based mating system where both sexes invest substantially into offspring (Trivers,1972). Women are expected to prefer men who are likely to provide much parental care in the form of active parenting and/or in the amount of resources they can provide. These men are, in turn, expected to be choosy about the women they select as mates (Trivers, 1972; Johnstone et al., 1996). The present chapter is not about this rather obvious link between mutual mate choice and offspring survival. Instead, we focus on probably less obvious aspects of mate selection that are likely to influence offspring viability. These include various genetic aspects that may play a role, e.g., inbreeding avoidance or preference for characteristics that are linked to heritable viability or to genes that may be complementary to the chooser's own genes. Genes of the major histocompatibility complex (MHC) have been intensively studied in this context. The MHC genes play a central role in controlling immunological self- and nonself recognition (Apanius et al., 1997). The MHC is also one of the most polymorphic regions of the genome, and it has been found to influence sexual selection.