Natural Selection and 'Darwinian Demons'

Why Do We Age?

In this lecture, Professor Luana Maroja (Williams College) poses the question: why do we age? Species that are around today have been evolving for millions of years, so surely evolution would ensure that individuals live longer (or indeed forever) to maximise the number of offspring they produce? To answer this question: (i) we first need to understand better the theory of evolution by natural selection, and the term ‘Darwinian Demon’; before (ii) understanding the biological theories of evolution that have intrigued scientists; following onto (iii) learning why these factors have not been ruled out by evolutionary pressures; before finally (iv) looking at examples of these evolutionary theories of aging in natural populations of possums and humans.

Natural Selection and 'Darwinian Demons'

In the first mini-lecture, we ask the question: why do we age? At first glance, it doesn’t seem like there is a clear answer. If we understand natural selection as a means of maximising lifetime fitness to produce more offspring, surely an individual that did not age would increase the population of a species much more than someone who did? Why also, do some organisms live longer than others, even between individuals of the same species? This first mini-lecture begins to tackle this question by understanding natural selection. We examine the three key components of natural selection that enable characteristics to evolve over time. To continue this, we learn about the term ‘Darwinian demons’: individuals that are long-lived or immortal, and consistently produce high-quality offspring. It is a term theorising the existence of species that do not follow Darwin’s theory of evolution by natural selection, and we learn about some species in nature that could be Darwinian demons.