This question "bothers" us only because it seems impossible today. Seeming impossibility, however, is not disproof. Any disproof would have to come from physical evidence, not conjecture or numerology.
Many ancient nations and historians have records of "unnaturally" long lifespans of the ancients:
Manetho, Berosus, Mochus, Hestiaeus, Hieronymus the Egyptian, Hesiod, Hecataeus, Hellanicus, Acusilaus, Ephorus and Nicolaus all state that the ancients lived around a thousand years.
Such records are found in the histories of ancient Sumeria, China, Greece, Persia, Vietnam and India. Such widespread agreement can only be because it (like the Creation) is a worldwide tradition based upon more than mere myth.

Answer 2
It is useful to look at the biblical lifespan for Methuselah in terms of numerology. First of all, the number 17 was important in Genesis genealogies, from Adam all the way down to the legendary Patriarchs. For Methuselah, the formula was simple, reflecting his status as the oldest man:

• he had his first child at the age of 187, which is 11 X 17,
• and died at 969, which is 57 X 17.
  

This question "bothers" us only because it seems impossible today. Seeming impossibility, however, is not disproof. Any disproof would have to come from physical evidence, not conjecture or numerology.

Many ancient nations and historians have records of "unnaturally" long lifespans of the ancients:Manetho, Berosus, Mochus, Hestiaeus, Hieronymus the Egyptian, Hesiod, Hecataeus, Hellanicus, Acusilaus, Ephorus and Nicolaus all state that the ancients lived around a thousand years.

Such records are found in the histories of ancient Sumeria, China, Greece, Persia, Vietnam and India. Such widespread agreement can only be because it (like the Creation) is a worldwide tradition based upon more than mere myth.
See also:

Longevity

Reliability of the Hebrew record

Tradition states that Methusaleh was one of the most righteous persons before the Flood, and the one who passed Adam's teachings on to Noah and whoever else was willing to listen.

The idea of such exceptional longevity "bothers" us only because it seems impossible today. Seeming impossibility, however, is not disproof. Any disproof would have to come from physical evidence, not conjecture or numerology.

Many ancient nations and historians have records of "unnaturally" long lifespans of the ancients:Manetho, Berosus, Mochus, Hestiaeus, Hieronymus the Egyptian, Hesiod, Hecataeus, Hellanicus, Acusilaus, Ephorus and Nicolaus all state that the ancients lived around a thousand years.

Such records are found in the histories of ancient Sumeria, China, Greece, Persia, Vietnam and India. Such widespread agreement can only be because it (like the Creation) is a worldwide tradition based upon more than mere myth.
See also:

Longevity

Reliability of the Hebrew Bible