Many biblical scholars who interpret the genealogies of Genesis 5 and 11 as yielding a continuous chronology from Adam to Abraham claim the Hebrew Masoretic Text (MT) preserves the original begetting ages for the patriarchs. The MT’s total for this period is 2008 years. The Samaritan Pentateuch (SP) presents markedly different chronological data for each epoch, for a grand total of 2249 years. Calculations derived from the primary manuscripts (MSS) of the Greek Septuagint (LXX) yield a chronology of 3394 years for this period, 1386 years greater than the MT. The MT is classically represented by the Ussher chronology, which places creation at 4004 BC and the Flood at 2348 BC. Figures from the LXX place creation at ca. 5554 BC and the Flood at ca. 3298 BC (Table 1; Appendix, n. 1). This paper proposes that the LXX preserves (most of) the original numbers in Genesis 5 and 11. Most of the MT’s chronology in Genesis 5 and 11 does not represent the original text, and is the result of a deliberate and systematic post–AD 70 corruption. Corroborating external witnesses, internal and external evidence, text critical and LXX studies, and historical testimonies will be presented, along with arguments rebutting LXX inflation hypotheses. Explanations for important, accidental scribal errors will be discussed, and a text critical reconstruction of Genesis 5 and 11 will be proposed.