I am taking a course in astrophysics and my teacher mentioned different biases that are present when taking a sample of galaxies: the progenitor bias and the Malmquist bias. I understand very well the Malmquist bias but I think that I don't yet really understand the progenitor bias.
What I get is that properties of low redshift galaxies (such as morphological type, ...) are not necessarily conserved when considering high redshift galaxies. What I mean is that, for example, an elliptical galaxy now might have been an elliptical, spiral or irregular galaxy in the past, while if we look at a high redshift elliptical galaxy it should have formed like that.
Am I right? Can you explain what the progenitor bias is in case I am mistaken?