User blog comment:NickFusi0n/A Theory on The Coordinate and The Wall Titans/@comment-200.83.222.106-20140611030035/@comment-4929778-20150822230711

Well remember that you cannot be born a Titan shifter, you have to inherit it by eating a previous Shifter. My theory though is that if you're from the Homeland they found a way to make everyone a Shifter, which is why RBA the beast Titan and Grisha are Shifters and why they are so skilled compared to Eren and Ymir.