The mass aggregation and merger histories of present-day distinct haloes selected from the cosmological Millennium Simulations I and II are mapped into stellar mass aggregation and galaxy merger histories of central galaxies by using empirical stellar-to-halo and stellar-to-gas mass relations .
The growth of bulges driven by the galaxy mergers/interactions is calculated with dynamical prescripitions .
The predicted bulge demographics at redshift z \sim 0 is consistent with observations ( ) .
Here we present the evolution of the morphological mix ( traced by the bulge-to-total mass ratio , B / T ) as a function of mass up to z = 3 .
This mix remains qualitatively the same up to z \sim 1 : \mbox { $B / T$ } \leq 0.1 galaxies dominate at low masses , 0.1 < \mbox { $B / T$ } \leq 0.45 at intermediate masses , and \mbox { $B / T$ } > 0.45 at large masses .
At z > 1 , the fractions of disc-dominated and bulgeless galaxies increase strongly , and by z \sim 2 the era of pure disc galaxies is reached .
Bulge-dominated galaxies acquire such a morphology , and most of their mass , following a downsizing trend .
Since our results are consistent with most of the recent observational studies of the morphological mix at different redshifts , a \Lambda CDM-based scenario of merger-driven bulge assembly does not seem to face critical issues .
However , if the stellar-to-halo mass relation evolves too little with redshift , then some tension with observations appear .