This case explores both the evidence and inconsistencies in the two major hypotheses for the origins of life on Earth: Replication-First or Metabolism-First. The case has two versions published on this website - one is written at the introductory level and the other at an advanced level for instructors to choose from based on their students' background.  The introductory version is most suitable for students in a first or second year biology course while the advanced version is suited for students in a third or fourth year undergraduate evolution course with previous biochemistry knowledge.  Using a "jigsaw intimate debate" format, students will gain a clear understanding of both hypotheses. The purpose of this format is to dissuade students from agreeing with one hypothesis, solely because they learned it first. Students, separated into groups, learn and then teach one hypothesis and then they switch and argue on behalf of the other.