The Y-chromosome provides researches a useful tool for studying different historical activities of our past, such as the development of ethnic diversity, language, religion, and human migration. It has also been used to help locate our species region of geographical origin.

Below you will find a summary of some landmark studies that involve the Y chromosome.

Landmark Research Studies and History:

One of the leading researchers in this interesting area of study which bridges DNA testing with Genealogy is Dr. Scott R. Woodward. Dr. Woodward is a Professor of Microbiology and faculty member of the Molecular Genealogy Program at Brigham Young University. He received his Ph.D. in Genetics from Utah State University in 1984. While at BYU he has been involved with the Seila, Egypt excavation team, directing the genetic and molecular analysis of Egyptian mummies, both from a commoners' cemetery and of the Egyptian Royal mummies. His research interests include the reconstruction of ancient and modern genealogies using DNA techniques with samples from all over the world. Dr. Woodward is currently involved with tracing the movements of human populations by following gene migrations (including both Old and New World populations) and the DNA analysis of ancient manuscripts including the Dead Sea Scrolls.

According to Chapter 5 of Genesis, Adam begat Seth, and Seth begat Enosh, Enosh begat Kenan, and so on. Translated into our modern genetic terminology, Adam passed a copy of his Y chromosome to Seth, and Seth passed a copy of his to Enosh, and so on. According to this Biblical account, the Jewish priesthood was established 3,300 years ago, when the first Israeli high priest was documented. Designation of Jewish males to the priesthood continues to this day. This spiritual lineage is determined through strict patrilineal decent. Dr. Michael Hammer, of the University of Arizona, and his collaborators set out to construct patrilineal genealogy cladrograms by using the Y chromosome's feature of being passed from father to son. Molecular biology techniques are being currently refined to unravel the mysteries of patrilineal inheritance.

Some of the published Y-chromosome STRs that are used to generate a Haplotype are shown in the Table below. GeneTree commonly uses either the the 24 STR System Marked Below to generate Y-haplotypes.

The human X and Y chromosomes, like those of other animals, have evolved from an ordinary pair of autosomes about 240 to 320 million years ago. This distinction has been pinpointed to have come after the divergence of the mammalian and avian lineages. The non-recombining regions of the X and Y chromosome have become highly differentiated over the years.

The Y chromosome has a low mutation rate. Therefore, mutations on the Y chromosome represent a record of its evolutionary past, and are used to assist genealogists and archeologists in their research. As long as a mutation does not affect the individual's ability to reproduce, it may be preserved and handed down to offspring. An exchange of a single DNA building block (i.e., a nucleotide) with another is called a Single Nucleotide Polymorphism (SNP), or a point mutation. Different combinations of polymorphisms on the Y chromosome are known as haplotypes. By looking at these changes biological relationships between 2 or more individuals can be established.

Dr. Peter Underhill, at Stanford University, has used Y chromosome SNP markers to discover genetic evidence that modern humans are descendants from a single migration of archaic Homo sapiens, found to have migrated out of Africa. The image on the left summarizes the findings that researchers studying the Y chromosome have concluded by studying the evolution of the Y chromosome.

The Y chromosome has also been used to study the colonization of Europe and the origin of some languages. The Finnish language is unique in Northern Europe, tracing its ancestry to the Uralic rather than Indo-European language family. This suggests that some of the Finnish genome originated in Northern Asia. But earlier genetic analysis showed that Finnish populations were closely related to the rest of Europe. Scientists have supported the hypothesis that the spread of language, not genes, accounts best for the uniqueness of the Finnish. However, Dr. Chris Tyler-Smith's group, at the University of Oxford, has discovered that Y polymorphisms abundantly present in Asia are also widespread in Finnish populations. They presented evidence of a migration out of Asia that is hard to refute. Nearly half of the Uralic-speaking Finns' Y chromosome lineages are similar to the central Asian Uralic speaking population. The study conforms to an interesting theory that the passing of a language from generation to generation is governed more by patrilineage than by matrilineage.

Another correlation study between the Y chromosome and linguistic heritage was carried out in Basques and geographically surrounding populations. The Basques have a unique language, which is very different from the languages of surrounding ethnic groups. Tyler-Smith's group and collaborators again used the Y chromosome markers to study if Basques' Y chromosomes are distinct from those of surrounding populations. Through this research, they uncovered a specific Y chromosome lineage, which has a recent origin and is rare or absent in most parts of the world. However, this Y chromosome lineage is shared with high frequency between Basques and Catalans, who speak languages belonging to different language families. These researchers presented evidence that supported the idea that there has been male-mediated gene flow, directly between Basques and Catalans, since the establishment of the languages spoken by them now. The polymorphism they studied was pinpointed to have occurred a few thousand years ago. Interestingly, the Basques Y chromosome lineages were also found in South America, which is not unexpected due to recent historical analysis regarding the ancient links between Iberia and South America. Interestingly, markers were also found in France, Germany and England.

Y chromosome fingerprinting can be useful by genealogists to study surnames and the history of their ancestry. Surnames in most European populations came into existence after the 13th century. Since the English Mediaeval period, it has been common practice for children to take their father's surname. Dr. Bryan Sykes, of the University of Oxford, proceeded to study the correspondence between the surname "Sykes" and Y chromosome haplotype. The highest residential concentrations of Sykes are in the counties of West Yorkshire, Lancashire, and Cheshire. Bryan Sykes and his colleague reported a highly significant association between Y chromosome haplotype and the Sykes sample. This work has very important forensic and genealogical implications. Mostly because such a method can be used to investigate the link between different branches of a family tree with the same surname for which a common ancestor could not be established from written records. A map of commonly used markers to type the Y chromosome can be seen on the right.

The Y chromosome became a popular tool for genealogists partly do to a DNA paternity test case that involved US President Thomas Jefferson. After the publication of an article in the scientific magazine Nature, co-author by Eugene Foster, a retired pathologist in Charlottesville, Virginia, the interest in the Y chromosome among genealogists has grown considerably. The story was first publicized in 1802, when President Thomas Jefferson was accused of having fathered a child. His putative son was Thomas Woodson, child of Sally Hemings, who was born in 1790, just after Jefferson and Sally Hemings returned from France. Members of the African-American Woodson family believed that Thomas Jefferson was the father of Thomas Woodson. The scientific team had the challenging objective of determining if descendants from Thomas Woodson were related to President Thomas Jefferson.

Sally Hemings had at least four more children. Her last son, Eston was born in 1808. Records point out that he had striking resemblance to Thomas Jefferson, which gave him access to white society in Madison, Wisconsin as Eston Hemings Jefferson. Eston's descendants believe that Thomas Jefferson was his father. Scholars who have devoted their efforts to studying President Jefferson's life maintain that Samuel or Peter Carr, sons of Jefferson's sister, fathered Sally Heming's latest children, including Eston.

The Foster team analyzed samples from five male-line descendants of two sons of Thomas Woodson, one male line-descendent of Eston Hemings Jefferson, and three male-line descendants of three sons of John Carr, grandfather of Samuel and Peter Carr. They reported the most probable explanation of their findings was that Thomas Jefferson, rather than one of the Carr brothers, was the father of Eston Hemings Jefferson. The researchers concluded that Thomas Woodson was not Thomas Jefferson's son.

The published data was scientifically challenged and, interestingly enough, took on a political spin. The challenge came from Herbert Barger of Fort Washington, Maryland, a genealogist and husband of a Jefferson family descendent. Mr. Barger helped locate living members of the Jefferson family and persuaded them to donate blood for the DNA study. However, he was not acknowledged in the article and his theory was not mentioned. Barger argues that the most likely farther of Eston Hemings is not Thomas Jefferson, who was 65 at the time Eston was conceived, but Jefferon's brother Randolph. The latter lived 20 miles away and was 12 years younger than Thomas Jefferson. Barger also theorizes that Randolph's sons are also candidate fathers. One of them, Isham, was reported to having parties in the same living quarters as Hemings. The political accusation was initiated by Reed Irvine, the Director of Accuracy in Media, a conservative organization based in Washington, D.C. Mr. Irvine claimed that the paternity case article was published in times when President Bill Clinton needed such a story on the eve of the US national elections, November 1998. This story demonstrates the importance of understanding inheritance, the power and limitations of paternity and distant family relationship testing, and more importantly, our readiness to deal with the interpretation of such data (Click here to see the Jefferson:Hemings published data, as maintained by Robert J. Huskey).

The Y chromosome is not only important for use in researching genealogical questions. It affects the expression of many traits. However, since the lack of knowledge correlating the differences between the Y chromosome and phenotypes among males is so limited, it is often referred to as the area of the unknown. A trait which is controlled by a locus found only on the Y chromosome is termed holandric. With the exception of azoospermia and possibly gonadoblastoma, pure holandric inheritance in humans is unknown. David Goldman of NIH, along with collaborators from Finland, were able to present evidence that differences among Y chromosomes contribute to variation in vulnerability to alcohol dependence. However, the authors point out, these differences do not demonstrate an association between Y haplotype and the personality variables thought to underlie the subtypes of alcoholism.

GenePool Assessment of Ethnicity or Population Patterns:

GeneTree offers the power of analyzing both the Y-chromosome and mtDNA for GenePool Population Assessment. GenePool Population Assessments can be done using autosomal DNA, the Y-chromosome, or the mtDNA. Currently, GeneTree is only providing the Y-chromosome and mtDNA for Native American GenePool Population Assessment (see our Find A Test page for this service).

Many people are interested in looking at the Y chromosome to help obtain an idea to their ethnicity. We are working to develop a system that will allow researchers to submit their Y chromosome haplotype data, and/or autosomal chromosome data, to calculate a probability of their ethnicity. An example of how allele frequencies vary between ethnic groups is seen in the Frequency DATA Graph to the right.

This DNA migration pattern map located on the right is created from compiled research on DNA populations around the world,. It demonstrates that the first Humans originated in Africa about 130-180 thousand years ago. Notes: a) mtDNA macro-lineage L is predominant in Africa, b) mt-DNA macro-lineages M and N are found throughout Eurasia and Australia, c) mtDNA lineages H, I , J, K, T, N, U, V, W and X are predominant in West Eurasia, d) mtDNA lineages A, B, C, D, E, F, G, M, P, Q and Z are predominant in Asia and Oceania, and e) mtDNA lineages A, B, C, D, and X are found in the Americas.

Y-Haplotyping Surname Example:

Y-chromosome Haplotype: Y-chromosome haplotypes can also be used for testing descendants with a common paternal link in their genealogical lineage. For example, if a group of males have strictly a male descent line (may have the same last name, such as Carmichael), and they are thought to all be related (the hypothesis in the study) to a common male ancestor, examining the Y-chromosomes of the individuals in common makes it fairly easy to support or disprove their hypothesis. By looking at Y-chromosome markers from all of the terminal males with the same paternal descent (all the males with the Carmichael Surname) we would suspect that they should all share the same Y-chromosome markers (with allowances made for calculated mutations that occur between generations, which should be a small number given less than 10 or 20 generations between 2 alleged paternally linked relatives). NOTE: This test could also be used to distinguish non-paternity in the line, a question that one might not want answered. So caution is advised when doing Y-chromosome Surname Studies.

Although this method is quite a useful tool for genealogists, it is not without its limitations. For example, examining the Y-chromosome haplotypes doesn't give a lot of information about degree of relatedness, just a type of inclusion or exclusion from the family. The figure on the right, Y-chromosome Inheritance Pattern, shows how the Y-chromosome (red squares) is passed from father to son, exclusively (males are represented by squares and females are represented by circles). See a sample Y-chromosome Surname Chart Below.

Name	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10	#11	#12	#13	#14	#15
Carmichael1	12	8	6	7	8	12	14	21	17	18	19	30	16	22	14
Carmichael2	12	8	6	7	8	12	14	21	17	18	19	30	16	22	14
Carmichael3	12	8	6	7	8	12	14	21	17	18	19	30	16	22	14
Carmichael4	12	9	6	7	8	12	14	21	17	18	19	30	16	22	14
Carmichael5	12	8	10	7	6	12	14	23	16	18	19	30	16	21	14
Carmichael6	10	11	6	7	8	14	12	21	15	16	18	28	15	20	14
Carmichael7	13	9	6	7	10	12	14	21	17	18	19	30	16	22	14
Carmichael8	12	8	8	10	8	12	14	23	17	18	18	31	16	20	14
Carmichael9	12	8	8	10	8	12	14	23	17	18	18	31	16	20	14

Y-Haplotyping Results:

Explanation for Y-chromosome Haplotyping Results
Y chromosome mutations generally occur once every 500 generations / locus (Heyer et al. 1997). Therefore, if we were to examine 24 loci, we would expect that one locus would show a mutation every 20.8 generations (i.e., 500 generations / 24 markers = 20.8 generations).

Key Terms:
MRCA (most recent common ancestor): The most recent common ancestor between 2 relatives.

MLE (most likely estimate): an estimate of when the most recent common ancestor between two relatives lived. This is most commonly presented in number of generations.