Yeasts capable of leavening bread are widespread,
Yeasts that can make bread fluffy are common.

and in the many centuries during which the ancient Egyptians made only unleavened bread, such yeasts must frequently have been mixed into bread doughs accidentally.

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 the author is speculating that such yeasts must frequently have been mixed into bread doughs?
Perhaps because such yeasts are widespread.

Why “accidentally”?
Not certain where the author got this from. Perhaps because the Egyptians made only unleavened bread for many centuries. So maybe ingredients capable of leavening bread were added accidentally. This reasoning could explain the use of the word ‘accidentally’, but I am open to other interpretations as I continue too

How come the bread was unleavened even though yeasts capable of leavening bread were frequently mixed into bread doughs, albeit accidentally?Perhaps something in the baking process caused the yeasts to not make the bread rise. (I understood this idea by relating this portion with the initial part: the phrase ‘yeasts capable of leavening bread’. These yeasts are “capable of leavening bread”. That doesn’t mean that if they are added, bread will rise for sure.)

The Egyptians, however, did not discover leavened bread until about 3000 B. C.
Although yeasts would have been accidentally mixed for quite a while, leavened bread was only discovered later (3000 B. C.). So bread only started rising in around 3000 BC (much later, I presume) for the Egyptians.

That discovery roughly coincided with the introduction of a wheat variety that was preferable to previous varieties because its edible kernel could be removed from the husk without first toasting the grain.
“That discovery” – what discovery? The discovery of fluffy bread
Around the same time that fluffy bread was discovered (3000 BC), a type of wheat was introduced. (Why are they talking about wheat? Ah! The main ingredient of bread.)

This type of wheat was preferable to previous types. We’re given a reason for the preference – because the non-edible part (husk) of the grain could be separated without first toasting.(‘edible kernel could be removed from the husk’ —> the husk was probably the non-edible part)


Gist:
1. Certain yeasts help make bread fluffy.
2. Such yeasts are very common.
3. Even though such yeasts must have been accidentally added to bread doughs, for many centuries bread didn’t rise.
4. The Egyptians started using a new variety of wheat.
5. This one did not require toasting of the grain.
6. X`Around the same time that the Egyptians started using this new variety of wheat, they discovered fluffy bread





Which of the following, if true, provides the strongest evidence that the two developments were causally related?

What ‘two developments’?

1. Discovery of leavened bread,
2. Introduction of the new variety of wheat.

“the two developments were causally related”

So,

• Either 1 caused 2
• Or, 2 caused 1

Do both these causal relations make equal sense?

• The discovery of fluffy bread caused the introduction of new wheat
• The introduction of the new wheat caused the discovery of fluffy bread

The first relation does not make sense; the latter one does. Right?

Framework: So, after reading the correct answer, I should believe more than I currently do in the notion that the Egyptians discovered fluffy bread because they had started using the new variety of wheat.

Perhaps the fact that the new wheat variety did not need to be toasted somehow led to the discovery.

Let’s see.





(A) Even after the ancient Egyptians discovered leavened bread and the techniques for reliably producing it were well known, unleavened bread continued to be widely consumed.
Incorrect.
Our job is to look for something that indicates a causal relation between the discovery of leavened bread and the introduction of the new wheat.
This option simply tells us that unleavened bread continued to be popular even after awareness about leavened bread had spread.
It does not help us establish the required causal relation. Irrelevant.

(B) Only when the Egyptians stopped the practice of toasting grain were their stone-lined grain-toasting pits available for baking bread.
Incorrect.
These “stone-lined grain-toasting pits” became available for baking only when they stopped toasting the grain. So, only after they started using the new variety of wheat.

So, earlier the Egyptians must have used some other pits, or some other form of an oven to bake bread.

This answer choice only talks about a new source of baking becoming available. It does not mention anything about whether this new source had anything to do with the bread becoming fluffy. So, this one is not helpful to establish the causal relation.

Now, what if the answer choice were:

(B’) Stone-lined grain-toasting pits became available for baking bread only after the Egyptians stopped the practice of toasting grain, and bread baked in these pits leavened.

This answer choice would have been correct.

1. Introduction of the new wheat would have led to stone-lined grain-toasting pits becoming available for breaking bread
2. Using these pits would have led to bread leavening
3. That’s how the Egyptians would have discovered leavened bread
4. So, introduction of the new wheat would have led to the discovery of leavened bread

The original one, however, does not tell us whether the kind of pit in which bread was baked was related to bread becoming fluffy.

(C) Heating a wheat kernel destroys its gluten, a protein that must be present in order for yeast to leaven bread dough.
Correct.
“a protein that must be present for yeast to leaven bread dough.” So, If the protein is not present, the bread will not leaven even if yeast is added.

How is “heating a kernel” relevant?

Oh, the new wheat variety did not require toasting (a form of heating); the old ones did.

The older varieties of wheat had to be heated initially. That would have destroyed their gluten. And that’s why bread wouldn’t have risen, even if there was yeast in the dough.

Now that the grain was not initially toasted, the protein would have remained in the wheat. And perhaps the gluten and the “accidental” yeast would have made the bread rise, leading to the discovery of leavened bread.

This answer choice does give me evidence that using the new variety of wheat led to the discovery of fluffy bread.

(D) The new variety of wheat, which had a more delicate flavor because it was not toasted, was reserved for the consumption of high officials when it first began to be grown.
Incorrect.
Who consumed this wheat does not help us establish a causal relation between the introduction of the wheat and the discovery of leavened bread. Irrelevant.

(E) Because the husk of the new variety of wheat was more easily removed, flour made from it required less effort to produce.
Incorrect.
Ok, but did the new wheat lead to the discovery of fluffy bread? All we learn is that flour from the new wheat required less effort to produce. We do not learn anything about how the Egyptians discovered fluffy bread. Irrelevant