The Lifespans

Genesis states how long twenty-eight men lived, and the figures are not scattered. Before the flood they hold flat at about nine hundred years. After it they fall — not raggedly, but along one smooth curve that flattens out just above a hundred years. Where that curve settles is the question this instrument is built to put to you.

What the two views show

The ages plots each man’s age at death against his place in the line of descent. The dashed line on the left is the mean of the nine pre-flood ages; the curve on the right is fitted to the eighteen ages after it.

Straightened subtracts the floor and takes the logarithm of what is left. If the decay really is exponential, that operation turns the curve into a straight line — and it does. That straight line is the entire claim, in one picture. Nothing else here is evidence; this is.

Enoch is drawn in red and left out of the fit. Genesis 5 closes every other name with and he died; his entry says instead that he walked with God, and was not, for God took him. His 365 years measure how long he was here, not how long a life lasted, so counting him would be counting a different thing.

The numbers

Before the flood, nine ages, mean 912, spread ±57 — no trend at all. Methuselah at 969 and Lamech at 777 are the extremes, and nothing in between is heading anywhere.

After the flood, eighteen ages on one exponential decay, R² = 0.927 with the floor held at 120. The excess above that floor halves every 2.8 generations: Shem is 480 above it, Peleg 119, Abraham 55, Moses none at all.

Let the fit choose its own floor rather than imposing 120, and it lands on 107.1 years, with a 95% confidence interval of 61 to 153. That interval contains 120. This is the strongest form the argument can honestly take: the numbers do not prove the limit of Genesis 6:3, but left to themselves they point at a floor, and 120 sits comfortably inside where that floor could be.

What this does not settle

Three things, and none of them is a small thing.

Genesis 6:3 may not mean a lifespan at all. His days shall be a hundred and twenty years is read two ways. Many commentators, probably most modern ones, take it as a countdown: God gives humanity a hundred and twenty years of respite before the flood. Others read it as a new ceiling on human life. Only the second reading makes the floor of this curve theologically interesting. The chart cannot decide between them; it can only show you that a floor near 120 is where the arithmetic tends.

And Psalm 90:10 says seventy, or eighty with strength — written, by its own heading, by Moses, who reached 120 himself. Whatever the limit is, ordinary life had already settled well below it.

A three-parameter curve fitted to eighteen points will fit almost any sequence that falls smoothly. R² of 0.93 says the shape is right; it does not say the shape is exponential rather than one of several others that would fit about as well. What makes the exponential reading more than a curve-fitting exercise is that its floor is not free-floating — the text names a number, and the data lands near it.

What the scholars say

Mainstream Old Testament scholarship does not read these figures as biological measurements. It reads them as schematic — numbers doing theological and literary work rather than recording a demography.

The strongest reason is comparative. The Sumerian King List, older than Genesis, gives its antediluvian kings reigns of tens of thousands of years, and then, after its own flood, the numbers collapse to something human. The shape this instrument draws — immense, then falling sharply after a deluge, then levelling — is a shape the ancient Near East already knew how to write. That does not make Genesis derivative, and it does not make its numbers false; but it does mean the shape is not by itself evidence of biology.

The second reason is textual. These very numbers differ between the three witnesses. The Masoretic Text, the Samaritan Pentateuch and the Septuagint disagree over the ages in Genesis 5 and 11 — most often over the age at fathering, but over some ages at death too. Lamech dies at 777 in the Hebrew, 753 in the Greek and 653 in the Samaritan. The curve above is fitted to the Masoretic figures. A Septuagint reader would be fitting a slightly different one.

Both points are worth holding at the same time as the pattern. The pattern is real: those eighteen numbers do fall on one curve, and that is a fact about the text whatever one concludes about its origin. What it is evidence of is the open question.

The figures used

Ages at death from Genesis 5 (Adam to Noah), Genesis 11 and 25, 35, 47 and 50 (Shem to Joseph), Exodus 6 (Levi, Kohath, Amram), Deuteronomy 34 (Moses) and Joshua 24 (Joshua). Every point on the chart carries its own verse — click it.

The four names after Jacob are not in the Genesis 11 style of list, but they continue the same line and the text gives their ages, so they are included: they are what carries the curve down to its floor, and Moses arrives at exactly 120.

The Timeline, for where these lives fall in history →  ·  Texts and datasets used →