The blood of a non-human ancestor flows in your veins.
Benefit: Choose another humanoid race. You count as both human and that race for any effects related to race. For example, if you choose dwarf, you are considered both a human and a dwarf for the purpose of taking traits, feats, how spells and magic items affect you, and so on.
Can a human with Racial Heritage take levels in an archetype that requires you to be of a specific race?
Yes, the Racial Heritage feat allows you to qualify for archetypes that have the chosen race as a requirement, assuming you still meet all of the other requirements to take levels in the archetype.
Advanced Player’s Guide. Copyright 2010, Paizo Publishing, LLC; Author: Jason Bulmahn.