The rotation curves of some star forming massive galaxies at redshift twodecline over the radial range of a few times the effective radius, indicating asignificant deficit of dark matter (DM) mass in the galaxy centre. The DM massdeficit is interpreted as the existence of a DM density core rather than thecuspy structure predicted by the standard cosmological model. A recent studyproposed that a galaxy merger, in which the smaller satellite galaxy issignificantly compacted by dissipative contraction of the galactic gas, canheat the centre of the host galaxy and help make a large DM core. By using an$N$-body simulation, we find that a large amount of DM mass is imported to thecentre by the merging satellite, making this scenario an unlikely solution forthe DM mass deficit. In this work, we consider giant baryonic clumps in highredshift galaxies as alternative heating source for creating the baryondominated galaxies with a DM core. Due to dynamical friction, the orbit ofclumps decays in a few Gyr and the baryons condensate at the galactic centre.As a back-reaction, the halo centre is heated up and the density cusp isflattened out. The combination of the baryon condensation and core formationmakes the galaxy baryon dominated in the central 2-5 kpc, comparable to theeffective radius of the observed galaxies. Thus, the dynamical heating by giantbaryonic clumps is a viable mechanism for explaining the observed dearth of DMin high redshift galaxies.