A key concept in Darwin's theory of evolution which suggests nature favours larger females that can produce greater numbers of off-spring must be redefined according to scientists behind ground-breaking research published today (3rd November 2015). The study, published in the scientific journal Biological Reviews, concludes that the theory of 'fecundity selection' – one of Charles Darwin's three main evolutionary principles, also known as 'fertility selection' – should be redefined so that it no longer rests on the idea that more fertile females are more successful in evolutionary terms. The research highlights that too many offspring can have severe implications for mothers and the success of their descendants, and that that males can also affect the evolutionary success of a brood. Darwin's theory of fecundity selection was postulated in 1874 and, together with the principles of natural selection and sexual selection, remains a fundamental component of modern evolutionary theory. It describes the process of reproductive success among organisms, defined by the number of successful offspring which reach breeding age.
After years of research, an evolutionary biologist from the University of Lincoln, UK, has proposed a revised version of the theory of fecundity selection which recommends an updated definition, adjusts its traditional predictions and incorporates important new biological terms. The research indicates that rather than aiding survival, too many offspring can be extremely costly, and can in fact reduce the lifetime reproductive success of females. It highlights that in many species, mothers who produce fewer offspring tend to raise them more efficiently, and that in some cases fathers can take the lead in nurturing young by evolving 'male pregnancy'.