Lifespans of the first 10 Generations

Did those in the first 10 generations truly live hundreds of years? or is this metaphorical, referring to the concept of a "life of many days", i.e. that the person has lived a full life, then the worth of Adam’s life would have been over 900 yrs, and the same for the rest of the 10 Generations. If it is literal, how is this possible? Modern scientific discovery has shown that people’s lifespans were shorter in the past. As a Torah-observant Jew, I find it hard to answer these questions, even to myself, in light of the scientific evidence.

According to the Rambam, certain episodes in the Torah are metaphorical. One could say the same about the lifespans of early generations. If the meaning is literal it would seem to be truly miraculous. I, for one, am reluctant to write miracles out of the Torah.