Astrophysics is making important advancements in our understanding of the origin of structure in the universe – over all scales. Nevertheless, a comprehensive description of galaxy evolution remains elusive due to the complex baryonic physics involved and the inherent challenges of studying high-redshift galaxy populations.  One of the key indicators of a galaxy’s nature and evolutionary history which has emerged is its environment – i.e. the density of the universe which surrounds it.  Still, it remains unclear if the environment plays a causal role in galaxy evolution, or if it is simply a tracer of underlying biases such as mass or formation time.

In this talk I will describe our on-going efforts at McGill to quantify the effects of the environment on galaxies.  We combine the unique repository of galaxy clusters to redshifts of z~1 provided by the RCS and SpARCS surveys, with deep infrared observations taken with the Spitzer Space Telescope to constrain the stellar mass assembly of galaxies in extreme regions.  I will outline the results of several different observational approaches aimed at distinct aspects of this problem, all of which highlight the difficulty in distinguishing the nurturing affects of clusters, from the inherent differences between the natures of galaxies in found different environments.