Did Abraham Know Noah?

Genesis 5 and 11 contain the most consequential numbers in the Bible. They record how long each patriarch lived before fathering the next in the line, how long after, and how long in total. Add them up, and you get a chronology from creation to Abraham. The problem is that the two oldest witnesses to these chapters — the Masoretic Text and the Septuagint — disagree on the numbers. Not by small amounts that could be scribal errors, but by exactly 100 years per patriarch, in a pattern too systematic to be accidental.

The result: the MT places Noah's death when Abraham is 58 years old. The LXX places it 722 years before Abraham is born. Someone changed the numbers. The question is who, when, and why.

The Numbers

Every genealogical entry in Genesis 5 and 11 follows the same formula, built on two Hebrew verbs: chayah (חָיָה, H2421, "lived," 270 occurrences) and yalad (יָלַד, H3205, "begat/fathered," 466 occurrences). The pattern is: "X lived N years and begat Y. And X lived after he begat Y another M years, and begat sons and daughters. And all the days of X were Z years, and he died."

Genesis 5: Creation to Noah (Pre-Flood)

The pattern is striking. For six of the first seven patriarchs (Adam through Enoch, skipping Jared), the LXX begetting age is exactly 100 years higher than the MT. The total lifespans are identical — the LXX subtracts the same 100 years from the remaining years after begetting. Someone added 100 to one column and subtracted 100 from the other, leaving the total unchanged.

Jared and Noah have the same numbers in both traditions. Methuselah and Lamech differ, but not by the clean +100 pattern.

The MT reads sheloshim ume'at shanah — "thirty and a hundred years" (130). The LXX reads diakosia kai triakonta ete — "two hundred and thirty years" (230). The verb structure is identical. Only the number changes.

Genesis 11: Flood to Abraham (Post-Flood)

The same +100 pattern appears in Genesis 11, now for six of eight patriarchs (Arphaxad through Serug). Nahor differs by +50 instead of +100. Shem and Terah match.

But Genesis 11 has a more dramatic divergence: the LXX inserts an entire extra generation. Between Arphaxad and Shelah, the LXX places Cainan (Καιναν), who lived 130 years before begetting Shelah and 460 years in total (LXX Genesis 11:12–13; absent in MT). This man does not exist in the Masoretic Text. Luke 3:36 (TAGNT) includes him in Jesus' genealogy — τοῦ Καϊνάμ — which means Luke followed a text tradition that had Cainan in it.

The Timeline

Here is what these numbers produce when you add them up:

In the MT, Noah dies in 2006 AM. Abraham is born in 1948 AM. Noah is alive until Abraham is 58 years old. Shem, who walked off the ark, is born in 1556 AM and dies in 2156 AM — 33 years after Abraham dies at 2123 AM. Eber (born 1723, dies 2187) outlives Abraham by 64 years.

According to the MT's own numbers, Abraham could have spoken with a man who survived the Flood. Shem was not a distant ancestor from a forgotten age. He was a living contemporary.

In the LXX, Noah dies in 2592 AM. Abraham is born in 3314 AM. 722 years separate them. No overlap. No possibility of meeting. The post-flood generations are spread across centuries, each patriarch fathering the next at 130+ years instead of 30.

The Pattern

This is not random scribal corruption. The differences are too systematic:

1. Exactly +100 years to the begetting age in 6 of 10 pre-flood patriarchs (Gen 5)
2. Exactly +100 years to the begetting age in 6 of 8 post-flood patriarchs (Gen 11)
3. Total lifespans usually preserved — the 100 is added to one column and subtracted from the other
4. An entire generation inserted (Cainan) in the LXX of Genesis 11

Someone deliberately adjusted the numbers. The question is direction: did the LXX's Hebrew source text (the Vorlage) preserve the original, with the MT tradition later reducing the begetting ages? Or did the MT preserve the original, with the LXX tradition inflating them?

The Cainan Problem

The insertion of Cainan between Arphaxad and Shelah in LXX Genesis 11:12–13 is the hardest data point for either side. The MT has no trace of him. But two other ancient sources do.

Luke's genealogy of Jesus includes him:

τοῦ Σαλὰ τοῦ Καϊνάμ τοῦ Ἀρφαξὰδ τοῦ Σὴμ τοῦ Νῶε

"of Shelah, of Cainan, of Arphaxad, of Shem, of Noah"

— Luke 3:35–36 (TAGNT)

And the Book of Jubilees (pseudepigraphal, 2nd century BC, attested at Qumran) not only includes him but tells a specific story about him:

"And he found a writing which former (generations) had carved on the rock, and he read what was thereon, and he transcribed it and sinned owing to it; for it contained the teaching of the Watchers in accordance with which they used to observe the omens of the sun and moon and stars in all the signs of heaven."

— Jubilees 8:3 (pseudepigraphal)

According to Jubilees, Cainan found and transcribed pre-flood inscriptions containing the forbidden astronomical knowledge of the Watchers — the fallen angels of 1 Enoch 6–8. He copied it in secret and hid it from Noah (Jubilees 8:4). In this telling, Cainan is the conduit through which forbidden knowledge survived the Flood.

Why would Cainan be removed?

The mathematics reveal something unexpected. If someone working in the MT tradition reduced each post-flood begetting age by 100 years, removing Cainan was not necessary to compress the timeline. In fact, keeping Cainan with MT-level numbers (begetting at 130) would place Abraham's birth at 2078 AM — 72 years after Noah's death. The overlap problem would not exist. Removing Cainan is what creates the overlap, pushing Abraham's birth back to 1948 AM and into Noah's lifetime.

This suggests that if the MT tradition reduced the numbers, Cainan's removal was motivated by something other than chronology. Jubilees provides a possible reason: Cainan's association with transmitting the Watchers' forbidden knowledge. As mainstream Judaism moved away from the Enochic literature in the late Second Temple and early rabbinic periods, a patriarch whose defining act was preserving angelic occult traditions may have become theologically undesirable.

This is inference, not proof. The textual evidence is:

• The LXX has Cainan (3rd century BC translation from a Hebrew Vorlage)
• Jubilees has Cainan with a specific Watcher-knowledge narrative (2nd century BC, attested at Qumran)
• Luke has Cainan (1st century AD, following the LXX tradition)
• The MT does not have Cainan (standardized 1st–2nd century AD)

The alternative reading: Cainan was never in the original Hebrew. The LXX translator added him — perhaps from a tradition like Jubilees — and Luke inherited the addition. In this reading, three witnesses (LXX, Jubilees, Luke) share a single non-original tradition rather than independently preserving an original one.

There is one more piece of evidence. Cainan does not appear only in Genesis 11. The LXX also inserts him in the Table of Nations: Genesis 10:22 (LXX) lists Cainan among the sons of Shem, and Genesis 10:24 (LXX) reads "Arphaxad begat Cainan, and Cainan begat Shelah." The MT of both verses skips directly from Arphaxad to Shelah. The same pattern holds in 1 Chronicles: the MT of 1 Chronicles 1:18 reads "Arphaxad begat Shelah" and 1 Chronicles 1:24 reads "Shem, Arphaxad, Shelah" — no Cainan in either verse. (Note: 1 Chronicles 1:2 contains the pre-flood Kenan, son of Enosh (H7018) — a different person from the disputed post-flood Cainan. The post-flood question concerns 1 Chronicles 1:18 and 1:24.)

This means either Cainan was added to three separate passages across two books in the LXX tradition, or he was removed from three separate passages across two books in the MT tradition. A single scribal error does not propagate across independent chapters. Whichever direction the change went, it was systematic.

The text does not resolve this. Both readings are defensible.

Sarah's Doubt

Genesis 18:11–12 records Sarah's reaction when told she would bear a child:

The text says chadal lihyot lesarah 'orach kannashim — "it had ceased to be with Sarah after the manner of women" (Genesis 18:11, MT). She had passed menopause. Her laugh was biological: her body was done.

Two readings of this moment are possible:

One reading, consistent with the LXX chronology: Sarah's doubt makes sociological sense because the age of extreme lifespans is centuries past. Nobody in living memory lives 400 years. A 90-year-old bearing a child is absurd in a world where 120–200 years is the normal range. The LXX's numbers place Abraham's generation far enough from the long-lived patriarchs that Sarah's reaction needs no special explanation.

Another reading, consistent with the MT chronology: Sarah's doubt is not about lifespan but about biology. Genesis 18:11 states the reason explicitly — menopause, not age. Even in a world where Shem is still alive at 548, a woman whose womb has closed does not expect it to open. The miracle is not that she is old but that she is done. The text says so.

Both readings have textual support. The first relies on the sociological implications of the chronological data. The second relies on the specific language of Genesis 18:11 itself.

Side Note: Jubilees

The Book of Jubilees (pseudepigraphal, 2nd century BC, attested at Qumran in 15 fragmentary manuscripts) preserves an independent chronological system using 49-year jubilee cycles. Jubilees 4:7 places Seth's birth at 130 AM — agreeing with the MT, not the LXX:

"in the fourth year of the fifth week [130 A.M.] they became joyful, and Adam knew his wife again, and she bare him a son, and he called his name Seth"

— Jubilees 4:7 (pseudepigraphal)

This is one data point, not a verdict. Jubilees was composed in the 2nd century BC and its chronological framework may have been derived from a Hebrew text tradition that already had the MT's numbers. It does not prove the MT numbers are original — it proves they existed by the 2nd century BC.

Side Note: 1 Enoch

The Book of the Watchers (1 Enoch 1–36, pseudepigraphal, 4th–3rd century BC, attested at Qumran in 4Q201 and 4Q202) describes the pre-flood world in detail but does not provide an independent set of genealogical numbers. Its portrait of the pre-flood patriarchs — particularly Enoch's 365-year lifespan and his role as scribe — aligns with both MT and LXX, which agree on Enoch's numbers (Gen 5:21–23). 1 Enoch is evidence for the Enoch tradition but not for the specific chronological dispute between MT and LXX.

External Witnesses

Two ancient historians outside the biblical manuscripts bear on this question.

Demetrius the Chronographer (3rd century BC) was a Hellenistic Jewish historian in Alexandria who produced the earliest known calculation of biblical chronology. His surviving fragments, preserved by later church historians, use the longer genealogical numbers — aligning with the LXX tradition. Demetrius wrote in the same century the LXX was translated, and his calculations predate any surviving MT manuscript by over a millennium. His witness does not prove the LXX numbers are original, but it proves the longer chronology was the standard reading among Greek-speaking Jews from the very beginning of the LXX tradition.

Josephus (Antiquities of the Jews, written c. AD 93) is a mixed witness. In Antiquities 1.143, he writes: "Sala was the son of Arphaxad" — omitting Cainan entirely, agreeing with the MT against the LXX. But in Antiquities 1.148, he gives the begetting ages using the LXX's longer numbers: "Arphaxad had for his son [Sala] at the hundred and thirty-fifth year of his age" (135 — matching the LXX, not the MT's 35). Josephus was a 1st century AD Jewish priest writing in Rome who had access to both Hebrew and Greek texts. He used the LXX's numbers while following the MT's genealogy — a mixed witness, not a clean confirmation of either tradition.

These two witnesses — one from the 3rd century BC, one from the 1st century AD — bracket the period in which the number traditions diverged. Both use the longer chronology. Neither is a biblical manuscript, so neither settles the question of which numbers are original. But together they indicate that the shorter MT numbers were not the universal reading in Jewish antiquity.

Typological Connections

The genealogical data in Genesis 5 and 11 is not merely chronological scaffolding. The text embeds theological markers within the genealogical formula itself — patterns that reward close reading.

The Death Formula and the Fall

Genesis 5 repeats a single phrase eight times: vayyamot (וַיָּמֹת, "and he died," from H4191 muth, "to die"). Adam — vayyamot (Gen 5:5). Seth — vayyamot (Gen 5:8). Enosh — vayyamot (Gen 5:11). Kenan — vayyamot (Gen 5:14). Mahalalel — vayyamot (Gen 5:17). Jared — vayyamot (Gen 5:20). Methuselah — vayyamot (Gen 5:27). Lamech — vayyamot (Gen 5:31). Eight deaths, eight repetitions of the same Qal wayyiqtol form, hammering a single point.

This refrain is not genealogical filler. It is the outworking of Genesis 2:17, where God told Adam: moth tamuth (מוֹת תָּמוּת, "dying you shall die" — H4191 muth twice, an infinitive absolute construction intensifying the verb). The same root, muth, that God spoke as warning in Genesis 2:17 becomes the narrative verdict over every patriarch in Genesis 5. Each vayyamot confirms that Adam's sentence extends to his line. The genealogy is a death register.

The Enoch Anomaly

The formula breaks exactly once. For Enoch (Gen 5:24), the expected vayyamot does not come. Instead, the text reads: ve'einennu ki-laqach 'oto 'Elohim (וְאֵינֶנּוּ כִּי־לָקַח אֹתוֹ אֱלֹהִים, "and he was not, for God took him"). Three words carry the weight: 'ayin (H0369, "is not" — negation of existence), laqach (H3947, "took" — Qal perfect, 927 occurrences, but in the context of removal from mortality it is unique in Genesis 5), and 'Elohim (H0430, "God").

The break is deliberate. Enoch walked with God — hithhalekh 'eth-ha'Elohim (הִתְהַלֶּךְ אֶת־הָאֱלֹהִים, Gen 5:22, 24). The verb halakh (H1980, "to walk") appears here in the Hithpael stem — a reflexive-iterative form indicating habitual, ongoing action. The phrase "walked with God" using the Hithpael of halakh with 'Elohim occurs in only two places in all of Genesis: here for Enoch (Gen 5:22, 24) and in Genesis 6:9 for Noah. These are the two men the text singles out by this exact formula from the entire pre-flood world.

Jude 1:14 identifies Enoch as "the seventh from Adam" — his ordinal position in the genealogy matters. Eight patriarchs receive the death formula (Adam through Lamech minus Enoch), and the seventh man from Adam is the one who escapes it. In a chapter where death reigns without exception, one man's entry testifies that muth is not absolute.

Methuselah's Death Year

The arithmetic embedded in the text produces a striking convergence. Methuselah was born when Enoch was 65 (Gen 5:21, MT) and lived 969 years (Gen 5:27) — the longest lifespan recorded in the canon. His birth year is 687 AM (by cumulative MT reckoning), placing his death at 687 + 969 = 1656 AM.

Noah was born in 1056 AM and was 600 years old when the flood came (Gen 7:6): 1056 + 600 = 1656 AM.

The text's own numbers place Methuselah's death in the year of the Flood. Whether he died in the Flood or immediately before it, the chronology is precise to the year. This may be coincidence. But the text nowhere says it is, and the arithmetic is not hidden — it sits on the surface for anyone who adds the numbers.

Methuselah's name (מְתוּשֶׁלַח, methushelach) has been parsed as a compound of muth (H4191, "death") and shalach (H7971, "to send") — yielding something like "his death shall send" or "when he dies, it shall be sent." This etymology is debated among lexicographers, and the text does not explicitly confirm it. But if the parsing holds, then Methuselah's name is a prophecy: his death and the sending of the Flood occupy the same year in the genealogical record.

The Lifespan Decline

The pre-flood patriarchs live 895 to 969 years (Gen 5:5–31). After the Flood, lifespans contract sharply: Shem lives 600 years (Gen 11:10–11), Arphaxad 438 (Gen 11:12–13, MT), and by Nahor the numbers are under 200 (Gen 11:24–25, MT: 148 years). Abraham lives 175 years (Gen 25:7). Moses records 120 years as the boundary (Gen 6:3, though the referent of this verse is debated). The Psalms name 70–80 years as the human norm: "The days of our years are threescore years and ten; and if by reason of strength they be fourscore years" (Ps 90:10).

The trajectory is clear in the text's own data: mortality tightens its grip across the generations. The eightfold vayyamot of Genesis 5 is the opening statement; the declining numbers of Genesis 11 are its confirmation. And in the middle of that death register, one man — Enoch, the seventh from Adam — walked with God and was not, for God took him (Gen 5:24).

What the Text Says and What We Infer

The text says:

• The MT and LXX disagree on the begetting ages of the patriarchs by a systematic +100 pattern (Gen 5:3, 5:6, 5:9, 5:12, 5:15, 5:21 for pre-flood; Gen 11:12, 11:14, 11:16, 11:18, 11:20, 11:22 for post-flood)
• The LXX inserts Cainan in Genesis 11:12–13; the MT does not have him
• Luke 3:36 includes Cainan, following the LXX tradition
• Jubilees includes Cainan with a narrative tying him to Watcher traditions (Jubilees 8:1–4)
• The MT chronology produces a 58-year overlap between Noah and Abraham; the LXX produces a 722-year gap
• Jubilees agrees with the MT's number for Seth's birth (130 AM)
• Demetrius the Chronographer (3rd century BC, fragmentary) uses LXX-aligned numbers; Josephus (1st century AD) uses the longer begetting ages but omits Cainan (Antiquities 1.143 vs 1.148)
• Genesis 18:11 gives a specific biological reason for Sarah's doubt

What we infer:

• The differences are deliberate, not accidental — the +100 pattern is too consistent for scribal error
• Someone changed the numbers — either the MT tradition reduced them or the LXX's Vorlage inflated them
• The external witnesses (Demetrius, Josephus) and the LXX's age as a translation (3rd century BC) suggest the longer numbers were the dominant Jewish reading through the Second Temple period. This does not prove they are original, but it shifts the burden of proof: the shorter MT numbers need to be explained as a later development, not assumed as the default.
• The LXX was translated from a Hebrew text in the 3rd century BC; the earliest MT manuscripts are medieval (though the MT tradition is attested at Qumran). Neither manuscript tradition's text can be dated by its manuscripts — both go back further than the surviving copies

The numbers matter. They determine whether Abraham's world still contained living witnesses to the Flood, or whether the Flood was ancient history by his time. The text preserves both possibilities. The ancient evidence — the LXX (3rd century BC), Jubilees (for Cainan, 2nd century BC), Demetrius (fragmentary, 3rd century BC), and Luke (1st century AD) — tilts toward the longer chronology as the earlier reading, though Josephus (1st century AD) is a mixed witness who uses the longer begetting ages while omitting Cainan (Antiquities 1.143). The reader must weigh the evidence.