The field of aging research is still in its infancy
Borrowed Time opens by introducing the dominant theory for why we age. This suggests that the majority of our bodies’ cells are only required until the next generation has been successfully raised. Since maintenance of cells is very energy intensive, there is a lack of investment once we pass our reproductive prime, much like an aging public transport system. This ‘disposable soma’ theory provides the framework for investigating how we age, and the book goes on to take a detailed look at the ideas surrounding this.