Christ mentioned the people of Tyre and Sidon, Sodom, Nineveh in Jonah's time, and finally the Queen of the South. All of these examples of people who lived in different generations are compared to the citizens living in the cities and towns of Jesus' day, the vast majority of whom did not understand or believe Christ's message. Jesus tells us that they are all to be resurrected with the generation that lived during His time!
Jesus gave enough examples of people living at widespread times to prove that most of humanity will be alive at the same time on this earth. There will be pre-Flood men and women, all twelve tribes of Israel, those who lived during the Middle Ages, and the vast majority living now. Even babies and children who died untimely deaths will be resurrected then. They will all rise in the second resurrection because they had not been called by God during their first lifetime.
This group includes all people of all times except those who will have already been born of God, and those relatively few individuals who already had their opportunity to receive eternal life, but deliberately rejected it, having sinned willfully. Those few will be resurrected in the third and final resurrection to be cast into the Lake of Fire (Revelation 20:14-15).
The ancient peoples Jesus mentioned in Matthew 11 and 12 would have repented if He had personally come to them in their day. And they will repent and receive the Holy Spirit when resurrected into a world that has been personally ruled by Jesus Christ for 1,000 years!
The Bible shows that the vast majority of those who have ever lived will finally be born into God's Family at the end of their coming period of judgment. God's master plan of salvation for mankind will then be complete.
How wonderful and reassuring is the truth of our all-wise, loving and merciful Creator God!