Recombination in primeval genomes: a step forward but still a long leap from maintaining a sizable genome.

A stubborn question in early molecular evolution is how to sustain the "minimum" informational length required for the basic features of life with a putative low-copying fidelity RNA polymerase ribozyme. Proposals to circumvent the information crisis have primarily focused on networks of cooperative molecules or compartmentalization of non-cooperative unlinked templates, but success has been very limited so far. Lehman (2003) has recently suggested that recombination--a frequently ignored player in early evolution--could have been crucial to building up primeval genomes of sizable length. Here we investigate this claim by assuming (without loss of generality) that genes were already enclosed in a compartment (vesicle, protocell). The numerical results show a quite intricate interplay among mutation, recombination, and gene redundancy. Provided that the minimum number of gene copies per protocell was enough for recombination to recreate wildtype templates--but not too high to impose an unbearable burden of mutants--informational content could have increased by at least 25% by keeping the same mutational load as that for a population without recombination. However, the upper bound of informational length would still be far from the "minimal life" provisions.