Scientists and philosophers have long struggled to answer the questions of when human life begins and when human life has inherent value. The phenomenon of identical (monozygotic) twinning presents a significant challenge to the view that human life and human personhood begin at conception. The fact that a single embryo can split to generate two (or more) genetically identical embryos seems to defy the notion that prior to splitting an embryo can be a single human individual. In "Untangling Twinning," Maureen Condic looks at the questions raised by human twinning based on a unique synthesis of molecular developmental biology and Aristotelian philosophy.
