DIFFERENTIAL FERTILITY OF MOTHERS OF TWINS AND MOTHERS OF SINGLETONS - STUDY IN LIMON, COSTA-RICA

The reproductive performance of mothers of twins is of interest from a n evolutionary perspective. Because mothers of twins have the potentia l of leaving a greater number of offspring, they could be favored by n atural selection. At the same time, twin pregnancies are known to be a ssociated with higher pre- and postnatal mortality. Thus mothers of tw ins at least have potentially higher fertility, a potential that may b e hampered by greater mortality of twins. Here, I examine the complete d fertility of 149 females, 50 years of age and older, from Limon, Cos ta Rica. In particular, the number of surviving children of mothers of twins and mothers of singletons at the time of the interview is compa red. In this sample mothers of twins have a higher fertility at the en d of their reproductive career. Their selection coefficient indicates that natural selection favors them through differential fertility.