In 1996, a Y-chromosome study fixed the date for the common ancestor of all human males at between 37,000 and 49,000 years ago.1,2 This study examined a large segment (100,000 nucleotide base pairs) of the Y-chromosome but in a very small sample: only five humans and one chimpanzee.
A more recent research project examined a much smaller portion of the Y-chromosome (729 nucleotide base pairs) in a slightly larger sample of humans (21), chimpanzees (2), orangutans (4), western gorillas (4), and an eastern gorilla (1)3. Except in the chimpanzees, researchers found no variations in this Y-chromosome segment within each primate species. Nor did they find any Y-chromosome differences between the western gorilla and the eastern gorilla. Significant differences were reported, however, between humans and gorillas, gorillas and chimpanzees, and chimpanzees and humans (comparisons were not done with orangutans).
The lack of variation within human, gorilla, and orangutan species suggests the relatively recent origin of these species. The significant chromosomal difference between species suggests that any common ancestor must date back to the far distant past. These two conclusions seem inconsistent, given the naturalistic assumption that all these species arise from a common ancestor.
How have scientists responded to this inconsistency? They speculate that Y-chromosome analysis may be, after all, an unreliable indicator of ancestry. To support their opinion, some have pointed out that the mitochondrial DNA date for humans' common ancestor is earlier than the date posited by corresponding Y-chromosome studies.
My response? I see that scientists remain hesitant to challenge the
assumption that all modern primates are descended from a common ancestor
through strictly natural processes. Further, the difference between the
mitochondrial date and Y-chromosome dates make sense. The mitochondrial
DNA analysis focused on women , not on men. And though it delivered more
ancient dates for the common ancestor of all women than did Y-chromosome
analysis for the common ancestor of all men, the difference is small, on
the order of a few thousand to a few tens of thousands of years. Such findings
are consistent with the biblical record. Scripture a significant time difference
between the common female ancestor of all women, Eve, and the common male
ancestor of all men, Noah.
So Noah, with his sons, his wife, and his sons' wives, went into the ark because of the waters of the flood. (Genesis 7:7) NKJV
Noah had no daughters, so his wife and the wives of his sons would still show and pass on the genetic differences between them from the time of Eve. However, all male humans will only show the changes from the time of Noah in their Y-chromosome. (Guy Cramer)
Depending on the number and duration of gaps in the Genesis genealogies (a subject debated among Old Testament scholars), the time difference between Eve and Noah could be anywhere from a few thousand years to a few tens of thousands of years.
The study based on 100,000 nucleotide base pairs of the Y-chromosome did show some variation within the human species. Variation among humans was measured at 0.00942 percent. The comparison of the five humans with the one chimpanzee showed a difference of 1.35 percent. These percentages suggests that Y-chromosome analysis cannot be totally unreliable as an indicator of ancestry. Definitive answers will require much larger sample sizes, certainly more than two or four or even a few dozen individuals, and analysis of more than a few hundred nucleotide base pairs.
- Hugh Ross, "Y-chromosome Reveals Evolutionary Limits," Facts & Faith, v. 11, n. 2 (1997), p. 5-6.
References from Hugh Ross:
1. Hugh Ross, "Searching For Adam," Facts & Faith, v. 10, n. 1 (1996), p. 4.
2. L. Simon Whitfield, John E. Sulston, and Peter N. Goodfellow, "Sequence Variation of the Human Y Chromosome," Nature, 378 (1995), pp. 379-380.
3. Wes Burrows and Oliver A. Ryder, "Y-Chromosome Variation in Great Apes," Nature, 385 (1997), pp. 125-126.
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