Evolution, Fertility and the Ageing Population

53 Pages Posted: 30 Jan 2013 Last revised: 4 Jan 2015

See all articles by Jason Collins

Jason Collins

The University of Western Australia - UWA Business School

Oliver Richards

Australian Treasury

Date Written: December 29, 2014


We propose that the recent rise in the fertility rate in developed countries may be the beginning of a broad-based increase in fertility towards above-replacement levels. Environmental shocks that reduced fertility over the past 200 years changed the composition of fertility-related traits in the population and temporarily raised fertility heritability. As those with higher fertility are selected for, the 'high-fertility' genotypes are expected to come to dominate the population, causing the fertility rate to return to its pre-shock level. We show that even with relatively low levels of genetically based variation in fertility, there can be a rapid return to a high-fertility state, with recovery to above-replacement levels usually occurring within a few generations. In the longer term, this implies that the proportion of elderly in the population will be lower than projected, reducing the fiscal burden of ageing on developed world governments. However, the rise in the fertility rate increases the population size and proportion of dependent young, presenting other fiscal and policy challenges.

Keywords: fertility, human evolution, ageing population, population growth

Suggested Citation

Collins, Jason and Richards, Oliver, Evolution, Fertility and the Ageing Population (December 29, 2014). Available at SSRN: https://ssrn.com/abstract=2208886 or http://dx.doi.org/10.2139/ssrn.2208886

Jason Collins (Contact Author)

The University of Western Australia - UWA Business School ( email )

Crawley, Western Australia 6009

Oliver Richards

Australian Treasury ( email )

Canberra, ACT 2600

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