The Bajorans weren't even the first Michael Westmore aliens with nose-ridge makeup -- see the Ornarans and Brekkians from TNG: "Symbiosis." Sometimes humanoids just happen to have similar appearances (as noted, there are many Trek aliens identical to humans).
On the other hand, it's true that if Bajoran history is as ancient as claimed, they could indeed have spread to the Gamma Quadrant in antiquity. Though Trek has been wildly inconsistent about that; "Ensign Ro" said they were civilized "when humans were not yet standing erect" (probably inaccurate, since hominins walked upright millions of years before humans evolved), yet "Explorers" claimed their "ancient" spaceflight era was contemporary with the Renaissance.
