No, it’s not literally true. It’s symbolic.
We sometimes forget that the primary method of teaching in Judaism (whatever it was called in any given period) was story telling. That’s why Christ’s own method of teaching was primarily to tell stories (which we call parables).
On the one hand, lengthy life was meant to express the righteousness of the person. In other words, the one who was more righteous was said to have lived longer.
Also, numbers in the Bible often have certain meaning. At first, they did not have true numerals like we do today. They wrote using letters. Somewhat like a code: a=1, b=2, etc. Occasionally, they used these numbers to spell words. Think of a telephone number that spells out a word.
The question “who was the earliest to deny the literal interpretation…?” is actually in reverse. These stories (early Genesis) were never meant to be taken literally. A good parallel example is the parable of the prodigal son. It was never intended to be literal history. Instead, it was always intended to make a spiritual point. In the same way, the early Genesis stories are meant to express some spiritual truth, but were never intended to be taken literally. We don’t see history until roughly the Abraham events (yes, Abraham was a real historical figure). We still have to be cautious though because the ancient peoples simply did not have the same understanding of history that we do today—where we try (or at least tell ourselves) that accuracy is important. Even today, the historian’s own bias always shows, even when nothing but hard facts are recorded.
Imagine if someone were to ask “when did people first deny that the parable of the prodigal son was literal history?” The question itself just doesn’t work.
