  The origin of life and the detection of alien life have historically been
treated as separate scientific research problems. However, they are not
strictly independent. Here, we discuss the need for a better integration of the
sciences of life detection and origins of life. Framing these dual problems
within the formalism of Bayesian hypothesis testing, we show via simple
examples how high confidence in life detection claims require either (1) a
strong prior hypothesis about the existence of life in a particular alien
environment, or conversely, (2) signatures of life that are not susceptible to
false positives. As a case study, we discuss the role of priors and hypothesis
testing in recent results reporting potential detection of life in the Venusian
atmosphere and in the icy plumes of Enceladus. While many current leading
biosignature candidates are subject to false positives because they are not
definitive of life, our analyses demonstrate why it is necessary to shift focus
to candidate signatures that are definitive. This indicates a necessity to
develop methods that lack false positives, by using observables for life that
rely on prior hypotheses with strong theoretical and empirical support in
identifying defining features of life. Abstract theories developed in pursuit
of understanding universal features of life are more likely to be definitive
and to apply to life-as-we-don't-know-it. In the absence of alien examples
these are best validated in origin of life experiments, substantiating the need
for better integration between origins of life and biosignature science
research communities.
