It is a virtual mathematical certainty that Jesus was a biological descendent of David. Let's consider the genealogist's dilemma.
- Go back one generation--your parents--you have 2^1 (2 to the first
power) of them
- Go back 10 generations--your 8th great-grandparents--you have 2^10 of
- Go back 20 generations--your 18th great-grandparents--you have 2^20
of them (just over a million)
David lived about a millennium before Jesus. If we allow for 25 years to a generation (not unreasonable for the time period), that's 40 generations. 40 generations back are your 38th great-grandparents and you have 2^40 of them. The trouble is, 2^40 is more than 1 trillion--and it's more than the total number of people who have ever lived on the earth.
1 trillion ancestors--how does that work?? It turns out if you go back far enough on your family tree you'll see the same names showing up on different branches. Your parents may not be closely related, but they are related--they have common ancestors. Those trillion names on the 40th generation branches of the family tree will be repeats of the same names over and over and over and over again.
This is why genealogists believe, for example, that everyone of western European descent is a descendant of Charlemagne. Not only did he have a lot of kids, but he lived almost 1300 years ago--the number of his descendants has multiplied exponentially, such that there came a point where even the handful of people who weren't his descendants would have an awful hard time finding someone to marry (in Europe) who wasn't a descendant of Charlemagne! I am a descendant of Charlemagne (too bad I didn't inherit his fortune though).
People who share a common regional ancestry are all related within 40 generations--and in a community like the Israelites, who tended to intermarry (see Deut. 7:3-4), it would take a lot less than 40 generations.
So yes, Jesus was a biological descendant of David. And so was every other Jew in Galilee.
Aside to guard against counter-arguments
It appears the math I've cited has caused some confusion--I'll briefly elaborate. I use 2^40 to make a point, but:
- The argument will work just fine if we use 2^39 instead (just over 500 billion), since Jesus had only 1 mortal parent.
- The argument will still work even if we use the condensed genealogy from Matthew, listing only 27 generations from David to Jesus: 2^27 is ~134.2 million. (I'm not suggesting Matthew's genealogy doesn't skip generations, just pointing out that using Matthew's genealogy as a counter-argument won't work)
- The argument works yet again if we combine both objections above, using 27 generations from Matthew and subtracting 1 from the exponent because Jesus had only 1 mortal parent: 2^26 is ~67.1 million, more than the total population of Jews in the Roman Empire in Jesus' time.
- Some have suggested a 25-year average generation is too high--that we should use a smaller number because of shorter lifespans. That's fine, it would only strengthen my argument by increasing the exponent.
Jesus' more precise claims
So what was significant about Jesus' claims of David descent? At least 2 things:
He could actually trace His genealogy back to David. For comparison, everybody on earth is descended from royalty somewhere, but most can't trace their lineage back that far.
He had legal, patrilineal claim as an heir of David. As a patrilineal descendant of David, Joseph had a plausible claim on the throne (though admittedly, not entirely without difficulty). As Joseph's adopted son, Jesus had a plausible claim as well (see discussion here). This is why, for example, several of Joseph's descendants were investigated by Emperor Domitian in case they posed a threat of claiming right to rule and thereby threatening Rome's rule over the Jews (see Eusebius, HE 3.19 & 3.20).
As noted in the comments, this means Jesus' brothers could also have claimed to be the Messiah...but the records suggest none of them ever did. Being a descendant of David did not automatically make one the Messiah--it was a necessary but not a sufficient condition.
Aside on adoption
Was Joseph Jesus' adopted father? Yes
From his own community we get the following:
And all bare him witness, and wondered at the gracious words which
proceeded out of his mouth. And they said, Is not this Joseph’s son?
And from Mary herself, after she & Joseph found Jesus (at age 12) in the temple:
thy father and I have sought thee sorrowing. (Luke 2:48)
What Matthew & Luke make clear is that Joseph was not Jesus' biological father.
The power of hostile witness
As you've noted, how do we actually know the claim of traceable Davidic descent is true? One of the criteria used to establish historical credibility is the testimony of hostile witnesses. If Jesus' enemies conceded something, that means it was pretty much incontrovertible.
The Gospels record multiple run-ins Jesus had with the religious leaders of His time, and they challenged Him on many points. His trial before the Sanhedrin is multiply attested in detail. And yet amidst their numerous challenges of Jesus' claims, person, and teachings, never do we find anyone challenging His well-known claim to be a descendant of David.
Some have suggested Jesus never claimed to be the Messiah--He does in Matthew 27:64:
63 But Jesus held his peace. And the high priest answered and said
unto him, I adjure thee by the living God, that thou tell us whether
thou be the Christ, the Son of God.
64 Jesus saith unto him, Thou hast said: nevertheless I say unto you,
Hereafter shall ye see the Son of man sitting on the right hand of
power, and coming in the clouds of heaven. (Matthew 27:63-64)
- Note that "Christ" is the Greek equivalent of "Messiah"
- The Greek idiom behind "thou hast said" here has often been garbled
in translation. The Greek is Σὺ εἶπας. As explained by Talmage:
This expression "Thou has said" was equivalent to -- I am what thou
hast said. (Jesus the Christ pp. 625-626)
The Synoptic Problem and the Genealogies
You noted in a comment that Matthew was not the first Gospel written. I respectfully hold a different view. My study of the Synoptic Problem has led me to the conclusion that both Mark and Luke were dependent upon Matthew. For a much more extended argument (if that's of interest), see my work on Matthean Priority here and the reliability of the Gospels here. (Matthean Priority = Matthew was first)
I recognize that most scholars believe in Markan Priority; I also recognize why they do so. For a brief discussion, see this post under the heading It’s the majority view among New Testament scholars: this is unremarkable given the history of the Synoptic Problem; for a more extensive discussion, see my videos here and here.
But this also creates a conundrum. If Luke used Matthew as a source--and I firmly conclude he did--why are the genealogies different?
As demonstrated on this site and many others, a definite answer on the differing genealogies is not universally acknowledged. But if Luke knew Matthew's Gospel and used a different genealogy anyway, that means one of two things:
- Luke thought Matthew was wrong (unlikely since he quoted hundreds of verses from Matthew)
- Luke had access to a different family line
I don't claim to know the answer for certain, but to me the most parsimonious solution is that one evangelist recorded Joseph's genealogy and one recorded Mary's.
That Jesus was a descendant of David we can establish on the math alone. That His genealogy could be traced to David is supported by hostile witness, and that His family could credibly claim patrilineal descent from David is attested by the fact that Emperor Domitian--politically the most powerful man in the world at his time--went to the trouble to track the poor family down.
Addendum--a personal note
(I'll move this to chat if the moderators don't approve of my having included this)
Hi Yeddu Prasad, welcome to the site, and thanks for sharing your thoughts. We all experience faith and doubt. To paraphrase Shayne Bowen: which one wins? The one that we feed.
If you are interested, there are two links I'll share.
A sermon I love by Dieter Uchtdorf: Doubt your doubts before you doubt your faith
My own epistemological journey, which has led me (much to the chagrin of some on this site) not to be bothered by potential discrepancies in the Bible, is described here.