These new tests, which relies on the other 22 chromosomes, the ones that are not the sex chromosomes.

There are advantages and disadvantages to autosomal testing. An advantage is that it can test across the entire family line, not just the paternal or maternal lines. In addition, both men and women can do this type of testing. A disadvantage of the autosomal test is that it is only useful for a few generations back, where the Y chromosome or mtDNA testing can detect the paternal or maternal lineage back for many generations, perhaps even hundreds or thousands of years.

Autosomal ancestry DNA testing will go back five generations fairly reliably. Back as far as second cousins can be determined without a doubt. Third cousins have some error and fourth and fifth cousins are a little fuzzier. However, you can test back to your great-great-great-grandparents with a fair degree of reliability. This is helpful for those who are tracing their family tree and are getting stuck three or four generations back, which is very common.

So what is the real use of autosomal testing? Well, if each of your 16 pairs of great-great-great-grandparents had lots of children and they had lots of children and so on, you could potentially have hundreds, if not thousands, of living relatives in the world. If any of them have taken the autosomal test, then you would be matched up with them. Some of these people may have additional genealogical information that you do not have and this makes it easier to build your family tree.

This type of testing is also useful when trying to determine relationships between deceased people. For instance, if there were two men who were thought to have been brothers, but the relationship is not certain, then testing their great-grandchildren to see if they have the appropriate second-cousin relationship would confirm the relationship of the deceased people. This is also very useful when building the family tree.

So how does this test work? Well, remember that your DNA is a mixture of DNA from your parents and their DNA is a mixture from their parents and so on. Lab technicians look at hundreds of thousands of pairs of locations in your autosomal DNA called single nucleotide polymorphisms (SNPs). These are compared to those of another person and the more of these identical segments two people share and the longer the segments are, the more closely they are related. While there may be coincident matches, generally speaking, anyone who shares these identical segments share a common ancestor.

For this reason, autosomal ancestry DNA testing is a fantastic way to expand your family tree and increase the number of family members attending your next reunion.