Y-chromosome studies have just answered a long-standing anthropological question: Are modern Japanese people descended from the Jomon or from the Yayoi people?1 The Jomon migrated to Japan from the Asian mainland about 12,000 to 14,000 years ago when sea levels were so low that land bridges permitted. The Yayoi arrived in ships from the Korean peninsula in about 250 B.C.
Research teams studied the Y-chromosomes of men all over Japan and throughout the eastern Asian coastlands. They also analyzed the Y-chromosomes from fossilized bones of ancient Jomon and Yayoi people. They found distinctive Y-chromosome markers of both Jomom and Yayoi progenitors in men throughout Japan. Slightly more Yayoi markers showed up in central Japan. Researchers conclude that the Yayoi initially landed in central Japan and subsequently spread north and south. As the Yayoi traveled and then settled, they apparently intermarried with the Jomon rather than supplanting them.
Even more definitively than the study on Jewish genes, this research on the Jomon and the Yayoi is helping researchers pin down rates and mechanisms of natural chromosome change. The advantages of the Japanese study are these: 1) it focuses on an island population that has been relatively stable for millenia, and 2) it can draw upon ancient DNA samples from the two migrant kiths.
The more we learn from chromosomal analysis, the better equipped we are to understand the development of life in Earth’s history. 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.2,3 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(l).4 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 gorillas 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 date makes 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. 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 suggest 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.
- John Travis, "Jomon Genes: Using DNA, Researchers Probe the Genetic Origins of Modern Japanese," Science News, 151 (1997), pp. 106-107.
- Hugh Ross, "Searching For Adam," Facts & Faith, v 10, n. 1 (1996), p. 4.
- L. Simon Whitfield, John E. Sulston, and Peter N. Goodfellow, "Sequence Variation of the Human Y Chromosome," Nature, 378 (1995), pp. 379-380.
- Wes Burrows and Oliver A. Ryder, "Y-Chromosome Variation in Great Apes," Nature, 385 (1997), pp. 125-126.