"Y-Chromosomal Adam" and "Mitochondrial Eve" are the names given to two ancient human beings who science has proved are genetic ancestors of every living person. Every man alive today is descended from "Y-Chromosomal Adam," while every man and woman alive today is descended from "Mitochondrial Eve."
Who are Y-Chromosomal Adam and Mitochondrial Eve?
The Y-chromosome is one of a pair of sex chromosomes determining gender. A woman has two X-chromosomes (one from her mother and the other from her father) and a man has one Y (from his father) and one X (from his mother). Because the Y-chromosome is passed down through the male line, researchers were able to trace the ancestry of humanity backward.
In the early 1990s, a group of researchers (Dorit, R.L., Akashi, H. and Gilbert, W. 1995. "Absence of polymorphism at the ZFY locus on the human Y chromosome." Science 268:1183–1185) ran an experiment in which they analyzed a segment of the human Y-chromosome, using 38 men from different ethnic groups. What they found was amazing: there was no difference at all in the base pairs of the segment they compared. In all 38 men the results were exactly the same. What this means is that every man alive descended from a single man. That person is now called "Y-Chromosomal Adam."
Something similar was found while studying mitochondrial DNA. Mitochondrial DNA is passed from mother to both sons and daughters. This type of DNA is never passed down from the father, so a maternal line can be established using mitochondrial DNA. Scientists were able to use this data to trace the ancestry of every person living back to one woman, who they now call "Mitochondrial Eve."
Creationists believe, naturally, that these two were the Adam and Eve described in the Bible—the first two humans. The science does not prove that Y-Chromosomal Adam and Mitochondrial Eve were the first two humans to exist—it only proves that every man living today is descended from the line of Y-Chromosomal Adam, and that all people living today are descended from Mitochondrial Eve. There could potentially have been other lines, from contemporaries of Y-Chromosomal Adam and Mitochondrial Eve, which died out and left no ancestor. However, we can say without doubt that every man alive today is descended from one man and everyone who is now living is descended from one woman.
"The man called his wife's name Eve, because she was the mother of all living" (Genesis 3:20).
Does the Bible mention prehistoric men such as cavemen or Neanderthals?
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Why did God create humanity?
Do Genesis 1 and 2 record two different creation accounts?
What does it mean that humanity is created in the image of God?
Truth about Creation