Schematic view of our results and findings. In the lower panels we plot the evolution of number density for low- and high-Σ MPGs (large green and small red dark spheroids, respectively). From z = 1.0 to z = 0.5 the number density of high-Σ MPGs does not increase, while over the same time period, the number of low-Σ MPGs increases by a factor 4. These new low-Σ MPGs are plausibly the direct descendants of MSFGs (blue spirals) that progressively halt their star formation until they become passive (see upper panels). In fact, we found that the observed increase in the number density of MPGs is totally accounted for by the observed decrease in the number density of MSFGs.