What is your point? That doesn’t mean it’s healthy. Thousands of years is literally nothing on an evolutionary scale. Modern humans have existed for at least 100,000 years.

Bread became ubiquitous because it didn’t require hunting or gathering, i.e. it supported ever growing communities of stationary humans. Not because some ancient nutritionist decided it was good for you.

My point? If you think a staple food vast numbers of human beings have relied on for literally all of recorded history (not to mention thousands of years prior) is "not particularly healthy", then perhaps your definition of "healthy" is a little too exalted for everyday use.