Critical to our understanding of life on Earth is the ability to judge the validity of claims of very ancient ‘fossils’. Martin Brasier’s most important contribution to this debate was to establish a framework within which to discuss claims of the ‘oldest’ life. In particular, Brasier et al. (2002) made it clear that the burden of proof must fall on those making the claim of ancient life, not those refuting it. This led to his formulation of the concept of the continuum of morphologies produced by life and non-life, and the considerable challenges of differentiating biogenesis from abiogenesis. Martin Brasier developed a set of criteria for distinguishing life from non-life, and extended the use of many new high-resolution analytical techniques to palaeontological research. He also applied this null hypothesis way of thinking to the origin of animals and the Cambrian explosion (Brasier 2009), leading to him being involved in the development of a series of nested null hypotheses, his “cone of contention”, to analyse enigmatic fossils more generally. In short, Martin Brasier taught us how to formulate biological hypotheses in deep time, established the rules for how those hypotheses should be tested, and championed a host of novel analytical techniques to gather the data required. As a consequence, future discussions of enigmatic specimens and very old fossils will be greatly enriched by his contributions.