#gmara

Masekhet Bekhorot Daf Khet Amudim Alef and Bet (8:a-b)  

“You are curséd than all of the domesticated animals and all of the wild animals”-If domesticated animals are curséd of wild animals [because ‘domesticated animals’ come before ‘wild animals’ in the pasuk] it is to tell you that just like the domesticated animal was cursed times seven than the wild animal the snake is cursed times seven than the domesticated animal.

And how do we know this?

The donkey (domesticated) was cursed seven times more than the cat (wild) [it is pregnant seven times longer][and the cat is pregnant, according to the gmara, for 54 days, which makes the donkey pregnant for 1 year, which makes the snake pregnant for 7 years].

Yalkut Shimoni Bereshit

A philosopher sought to know the gestation period of a snake. He saw some mating, captured them, placed them in a vessel, and fed them. When the elders arrived in Rome, they saw Rabban Gamliel, and asked him, “How long is the snake pregnant for?” He was not able to answer them, and his face fell.

Rabbi Yehoshua met him, and asked him why he looked so down. He replied, “I was asked one question, and I was not able to answer it.” 

Rabbi Yehoshua asked, “What was it?” He answered, “How long is a snake pregant for?” Rabbi Yehoshua said, “After seven years.”

Rabban Gamliel asked, “How do you know?”

Rabbi Yehoshua replied, “The dog is an impure wild animal, and gives birth after fifty days, and an impure domesticated animal gives birth after twelve months; and it says, ‘You are cursed from all the domestic animals and from all the beasts of the field’ – just as a domestic animal is cursed seven times more than a wild animal, so too is the snake cursed seven times more than the domesticated animal. 

Towards evening, Rabban Gamliel went out and told the philosopher. THe began to bang his head against a wall, and said, I worked and exerted myself for seven years [to discover this], and this one comes and holds it out on a cane [finds it our so easily].

So how long is a snake actually pregnant for?

3 months-9 years.

This is because some species can do this thing where they store the sperm instead of egging it immediately, which leads to healthier babies.

In conclusion, past people were very confused, and rightfully so.