Each person inherits two copies of the approximately 3 billion chemical letters ("A", "T", "G" and "C") of the human genome—one copy from each parent. Mutations—changes to the DNA sequence—happen every generation, making each individual genetically different from every other individual.
The accumulation of these differences resembles "ticks" of a "clock," counting the time since any two people last shared a common sequence.
Y-chromosomal Adam was a real person, but is named after Adam from Book of Genesis in the Old Testament of the Bible.
Sophia Putney-Wilcox: I kept saying to my mom, “I’m going to die, I’m going to die, I’m going to die,” and she was like, “Sophie, it’s OK.” Kristin Putney | Sophia’s mother: I just tried to be as calm as I could and try to just reassure her. Kristin Putney: Two officers were waiting there for us. And I believe this is what I’m here for, to share my story.
Sophia Putney-Wilcox: The police came in and were just asking me questions. ” I just said “yes.” And that’s the last conscious memory I have before my surgery. “Oh my God, I’m alive.” I just felt there’s a reason I’m here.
It is usually taken for granted by those interested in Biblical chronology that the year 4,004 BC as first proposed by Archbishop Ussher, give or take a few years, is the date the book of Genesis gives for the date of creation.
The Jews use a slightly different chronology first proposed by Rabbi Yossi, a disciple of the great Rabbi Akiva which proposes a date of 3760 BCE largely on account of a misunderstanding of the Persian period.
Two new studies suggest that female "mitochondrial Eve" lived at roughly the same time as "Y-chromosome Adam." However, the assumptions they used to reach this dating concordance demonstrate the classic circular reasoning that besets evolutionary age calculations.