The paper covers the analogical parallel between biological evolution and language evolution, as it is intended within the biolinguistic perspective, with the aim of accounting for some relevant features of the evolutionary process undergone by grammars. The idea is to systematize hypotheses on the applicability of the evolutionary model outlined in biology to diachronic syntax, favouring the illustration of different perspectives that have been put forward so far. The goal is to provide a scheme in which the parallel can be framed, and to show how the biolinguistic approach on grammatical change plays an essential role in shedding light on the issue. The investigation appears to encourage the idea that biological and syntactic evolution may be modelled following comparable guidelines. Even if some specific factors are shown to be deeply different, it seems reasonable to think that some aspects of the two processes can be studied by means of analogous methods of investigation.