Today population genetics and quantitative genetics describes some of this from different angles, and indeed finds that stochastic distributions can model such processes as mutations, drift and migration. ( <a href="http://scienceblogs.com/gnxp/2007/03/population_vs_quantitative_gen.php">http://scienceblogs.com/gnxp/2007/03/population_vs_quantitative_gen.php</a> )