Abstract
It is proposed that when, in evolution, a structure loses its function, it does not always subsequently become reduced in size and thus vestigial. However, when useless structures do become vestigial they may do so for a variety of different reasons in different cases. Direct selection for reduction, pleiotropy, genetic drift, and meiotic drive are all factors which from time to time may happen to produce vestigial structures. Another factor, recurrent mutation, is considered a highly unlikely explanation for very many cases.

This publication has 3 references indexed in Scilit: