מדרש על זבחים 224:11

(Devarim 12:8) "You shall not do as all that we do here today": As long as the mishkan (the tabernacle) had not been established, the bamoth (individual altars) were permitted, and the (sacrificial) service was performed by the first-born. When the mishkan was established, the bamoth were forbidden and the service was performed by the Cohanim.