  We illuminate the nature of the three-dimensional random walks of
microorganisms composed of individual organisms adhered together. Such
$aggregate~random~walkers$ are typified by choanoflagellates, eukaryotes that
are the closest living relatives of animals. In the colony-forming species
$Salpingoeca~rosetta$ we show that the beating of each flagellum is stochastic
and uncorrelated with others, and the vectorial sum of the flagellar propulsion
manifests as stochastic helical swimming. A quantitative theory for these
results is presented and species variability discussed.
