A puzzle, particularly a jigsaw puzzle, can serve as a useful metaphor for the origin of life problem, although the figurative puzzle must be unusually challenging. Ordinarily, a jigsaw puzzle provides well-defined pieces that are just sufficient to complete a picture or design; however, in this case, it is complicated by missing pieces (some irretrievably lost and others perhaps yet to be found), pieces that no longer have their original shapes, and other pieces that are perhaps irrelevant, that is, that come from other puzzles and have accidentally been added to the mix. Consequently, the puzzlers (origin of life scientists) work, hoping that these difficulties will not, in the end, be insurmountable – that the irrelevant pieces can be culled, and that those remaining can be properly arranged and will be sufficient to show the outlines of the overall picture or design.

One of the puzzle pieces is a record of early Solar System organic chemical evolution found in a class of meteorites called carbonaceous chondrites. It is a well-defined piece, with fairly sharp edges and much of its original color still showing. It seems to interlock with adjacent pieces – but, is it relevant? The nature of the organic matter and its accretion by the early Earth suggest that it is.

Theories of the origin of terrestrial life, with the exceptions of panspermia (Arrhenius 1908) and those that posit an inorganic, that is, “clays first,” origin (Cairns-Smith 1982), require preexisting organic (reduced carbon) compounds as raw material for self-assembly of the progenote, the earliest life form (Haldane 1929; Oparin 1938).