Seamus Blackley/TwitterA researcher-slash-baker successfully baked a sourdough loaf from 4,500-year-old yeast. Bread has been a common staple for many cultures around the world since ancient times.
It's very easy to make a Basic Sourdough Starter without yeast. It takes a bit of time, but the results are amazing and well worth it. There is nothing like a freshly baked loaf of sourdough bread.