It's the grandparent of Islam and Christianity and one of the world's oldest surviving religions, by some counts dating back nearly 4,000 years. This, at least, has long been a common view of Judaism. But now an Israeli archaeologist is challenging those long-held assumptions. Based on 15 years of studying textual and archaeological evidence, Yonatan Adler of Ariel University, in the West Bank, concludes that ordinary Judeans didn't consistently celebrate Passover, hold the Sabbath sacred or practice other traditional forms of Jewish ritual until a century or so before the birth of Jesus. If his theory proves correct, then Judaism is, at best, Christianity's elder sibling and a younger cousin to the religions of ancient Greece and Rome.