Genealogy is a line of descendants traced continuously from an ancestor.
The Bible is replete with the genealogies of the most important characters. The Biblical narrative can be traced sequentially and almost unerringly for 5764 years. The Quran on the other hand, shows a total and conspicuous lack of interest in the genealogies of any of its main actors; it does not have a single case of genealogy of any of them. The Ahadith too, show this remarkable omission. The answer is of course simple since Muhammad could not provide any not even for the most illustrious of his alleged ancestors: Ishamel/Ismail.
Since even according to the Quran and the earliest Ahadith, that the pagan Arabs had NO KNOWLEDGEof previous revelations, then they neither knew about Abraham nor about Ishmael except what was inserted later on by the followers of Muhammad. The Quran only asserts that both Abraham and Ishmael were Muslims; that is, they believed in the One and only Allah.
There is not even a hint that they were the ancestors of the Arabs since Arab tribes existed in the Penisula centuries before Abraham was borne.
It was for their utter lack of a true ancestral genelogy that the later followers ofMuhammad concoted and created a mytholgical ancestral line leading from Muhammad to Abraham and of course to Adam, especially since not a single one of them is able to give any references upon which they base this lineage nor the time-line concerned. They do not give dates of birth and/or death or the ages of the characters concerned.
Almost 90% of the names of their alleged ancestors are copied, pirated, plundered and or perverted from the Bibleto start with; otherwise they would have absolutely no 'leg' to stand on. Of course they did this with impunity in spite of their allegations that both the Jews and Christians had deliberately 'tampered'with the Biblical records.
When studying the Ahadith, they unfortunately give contradictory and different genealogies for the same Biblical characters making it impossible to depend on the veracity of any of them.
Let us assume for arguments sake that that there is a Muhammadan genealogy and let us analyse their alleged 'record':
According to Ibn Ishaq in his 'Sirat Rassoul'Allah' - the first biography of Muhammad (AG's translation pages 3-4) - there are 49 generations from Adam to Muhammad. Assuming - to be realistic and conservative - that each generation starts at the age of 40 years, a simple calculation yields 40 X 49 = 1960 years passed between Adam and Muhammad.
Since Muhammad was born c.570CE, then Adam was born 1960-570 = 1390 BCE only; in the days of the Pharaohs of the New Kingdom.
Using the Hebrew calendar and taking the year 2004 CE as the starting point and working backwards, we get the following calculations and result:
2004 CE = 5764 Hebrew (since the creation); less 1434 years since Muhammad's birth (570 CE) = 4330; less 2035 years from Adam to Ishmael = 2295 years from Ismail to Muhammad(29 generations) averaging an almost impossible 79 years per generation.
Taking the time line from Adam to Muhammad we get the following: 5764 - 1434= 4330 /4 9 =88 years per generation.
Hence, no matter how one calculates the dates and numbers of Ismail's alleged ancestors, nothing makes sense for the simple reason that all of Muhammadan Islam is based upon a concocted 'belief system' which is utterly devoid of facts or reality.