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We examine the evolution of assembly bias using a semi-analytical model of galaxy formation implemented in the Millennium-WMAP7 N-body simulation. We consider fixed number density galaxy samples ranked by stellar mass or star formation rate. We investigate how the clustering of haloes and their galaxy content depend on halo formation time and concentration, and how these relationships evolve with redshift. At z = 0 the dependences of halo clustering on halo concentration and formation time are similar. At higher redshift, halo assembly bias weakens for haloes selected by age, and reverses and increases for haloes selected by concentration, consistent with previous studies. The variation of the halo occupation with concentration and formation time is also similar at z = 0 and changes at higher redshifts.
Contreras et al. (Tue,) studied this question.