 Centaurs and TNOs that reach the inner Solar System can modify the orbits of main belt asteroids, though only if their mass is of the order of for single encounters or, one order less in case of multiple close encounters.However Centaurs and TNOs are unlikely to have significantly dispersed young asteroid families in the main belt, but they can have perturbed some old asteroid families.Current main belt asteroids that originated as Centaurs or trans-Neptunian objects may lie in the outer belt with short lifetime of less than 4 million years, most likely between 2.8 and 3.2 AU at larger eccentricities than typical of main belt asteroid.