'This may come as some surprise' to Asch & Aumann, but rationality is not the design point of the human brain (otherwise this blog would have no reason to exist), getting by in the real world is. And getting by in the real world involved, for our ancestors through tens of millenia, group belonging, hence group conformity. See J. Harris, 'No Two Alike', Chaps. 8 & 9 for a discussion which references the Asch work. This does not mean of course that group conformity was the only adaptation factor. Being right and being 'in' both had (and have...) fitness value, and it's pefectly natural that both tendencies exist, in tension.