The notion, suggested by Francis Crick and Leslie Orgel (1973), that Earth’s first living...

The notion, suggested by Francis Crick and Leslie Orgel (1973), that Earth’s first living things were sent here intentionally by an advanced civilization is known as the directed panspermia hypothesis. Orgel admitted to John Horgan (1991) that he and Crick intended the hypothesis as “sort of a joke.” In their 1973 paper, however, Crick and Orgel treat the idea seriously enough to consider biological patterns that might serve as evidence. They point out, for example, that it is a little surprising that organisms with somewhat different [genetic] codes do not exist. The universality of the code follows naturally from an “infective” theory of the origins of life. Life on Earth would represent a clone derived from a single extraterrestrial organism.

Since 1973, biologists have discovered that the genetic code is not universal and that organisms with “somewhat different codes” do, in fact, exist. Our mitochondria, for example, use a code slightly different from that used by our nuclei (see Knight et al. 1999). Many ciliates and other organisms also have slightly deviant codes (see Osawa et al. 1992). How strongly does the discovery that the genetic code is not universal refute the directed panspermia hypothesis? How strongly does it refute other versions of panspermia? Explain your reasoning. Can you think of other kinds of evidence that could (or do) either support or refute some version of panspermia?