TheStory
Yeasts capable of leavening bread arewidespread,
Yeasts that can make bread fluffy arecommon.
and in the many centuries during which the ancient Egyptians made only unleavened bread, such yeasts must frequently have been mixed into bread doughsaccidentally.
For many centuries ancient Egyptians made only non-fluffy bread.
During those times, such yeasts must have been added into bread doughs accidentally.
“must … have been” indicates that this is a speculation.
How come
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