Records of long Life

The longest recorded life spans I have found are in the Bible.

I don't know how accurate those records are, and there are aspects of those records that are extremely interesting - even intriguing.
The intrigue got me when I first graphed the ages (in 1975 - see below).

Ages of the Patriarchs

It looked to me like a set of steps.

It looked like the sort of steps a genetic mechanism would give rise to.

I did some maths on it.

The first 9 generation have an average age of 913, with a standard deviation of 54.
The next 4 have an average of 484, with an SD of 68.
The next 3 have an average of 236, with an SD of 4.
It halves, then halves again.

Why would anyone invent a pattern like that?

Isn't it simpler to believe that it might be an accurate record with an as yet unknown genetic cause?

What exactly might have been the mechanism that caused it?
(I won't go into musings on that subject here, and I have had some.
If you have some experience of genetics, try it yourself.)