Brief Discussion of CHASE / CHACE Paternal
The following discussions make some necessary simplifications so that things don’t get too technical.
First, let’s review what the individual tests show, why there are differences in some of the sets of numbers displayed for each person, and what these differences mean.
The individual test
results displayed in the table show the values of each person’s
It is important to understand up front that these tests cannot identify who a common ancestor might be. But they can serve to suggest which individuals probably do (or do not) have a “recent” common ancestor, and help prove or disprove other information that may point to him. And we say “him” because these tests are for genetic values of the Y chromosome, which is passed down only through the male line of a family.
The values of these genetic markers change (mutate) slowly over generations, which is why individuals even with a relatively recent common ancestor can have slightly different values for one or more of them. Since the genetic mutations of any given marker are random (that is, they don’t happen with predictable regularity between generations), we cannot predict exactly how often they occur. However, geneticists have been able to calculate the mean probability that a mutation will occur in any one generation, and this provides a way to estimate the time back to a “most recent common ancestor” (MRCA) based on the number of observed mutations (that is, the number and size of differences in the values of the markers tested) by which the Y chromosomes from two individuals differ. As one includes more and more markers in the test, the probability distribution becomes tighter and tighter about its mean value, and estimates of the number of generations back to a MRCA have higher precision.
But since the estimates are based on probabilities, there are no absolute certainties. This is especially important when comparing individuals using only 12 marker test results. In this case, even a “perfect” 12 out of 12 match between two individuals cannot, by itself, be interpreted to mean the two definitely have a “recent” common ancestor. Other genealogic evidence is required to validate this determination.
INTERPRETATION OF CHASE/CHACE
Six of the
participants who have been unable to identify their ancestry line had a 37
marker test done. The very close 25 marker match (only a 1 step difference in
one marker) with the three participants who have identified their Aquila
ancestry through documentation makes it highly probable that they descend from
Aquila (or Thomas, since both would have the same
participants who are uncertain of their ancestry had a 12 marker test done with
results that match those of known
2. William line descendants (Yellow on the chart)
A William ancestry has been established through research of records by seven participants, and their identical 12 or 25 marker tests confirm a probable MRCA within the last 14 generations (50% probability level), consistent with their prior research. The matches of 25-marker tests for other participants in the Yellow section (none of whom have traced their lineage back to an American progenitor) with those of the known William descendants provide a very high probability that they, also, are William descendants. (Before being tested one of these individuals assumed he was descended from
Family Lines (Light green on the chart)
Both #8797 Laurence Chase, who has traced his ancestry to an 18th century Samuel Chase in Bedfordshire, England, and #11634, Andrew Chase, who lives in England, have indicated they have some unspecified ancestral tie to the Chesham Chase line. However, the large number of mismatches between the two suggests that no common ancestor is likely within many, many generations.
Of perhaps more interest is the lack of any even reasonably close match between the 25 marker tests of either Laurence or Andrew and those of the known
#6754 George G., a
non-Chase surname who has been unable to trace his ancestry. While there are
some similarities with the dna of known
Updated August 2009