Since evolution is the reproduction of a new genotype instead of a previous one, I don't doubt that the selection pressure they applied couldn't select for multicellularity. Also interesting, the author points out: If we select for more rapid settling, snowflake yeast evolve to delay reproduction until the parent is larger, allowing it settle more quickly. We see the evolution of higher rates of apoptosis as a way to regulate the size and number of propagules produced. That's pretty nice. IMHO, people tend to think that evolution is more magical than it is. If you've got a quickly reproducing organism with some genetic variation occuring, and you can apply consistent pressures, you should see selection for genotypes occur. It's just cool that they apparently could select for multicellularity.