It is quite common for women to recruit a brother, father, male cousin or nephew to act as a surrogate donor of y-chromosome DNA for testing to establish paternal lineages. Other ingenious uses of surrogates can be made to test specific hypotheses. For example, surname DNA projects often test a carefully selected sample of the present day male descendants of a family patriarch many generations back. This can lead to information that is very helpful in grouping his descendants and separating out non-descendants.
In like manner, surrogate donors can be useful for mitochondrial testing. For example, my paper research trail indicated that a sixth-great-grandfather had taken as his third wife a woman reportedly named Marjory Owens. So far I have only found her surname in one marriage document. Generally, Owens is considered to be a surname of Welsh origin. There are known to have been Owens from Wales in nearby Maryland around that time--early 1700s. However, Henry and Marjory lived in an area that had been settled as New Sweden and now is part of present day Delaware. Henry's father had come from Sweden along with his family. So I was left to wrestle with the question of whether Marjory was of Swedish or Welsh ancestry.
Marjory was a direct maternal ancestress of my grandmother. Unfortunately, it was the wrong grandmother. I could not use my mitochondrial DNA sample to test for a relationship because Marjory was an ancestor of my father through his mother and my father was deceased. To explore this relationship I recruited a first-cousin who was the daughter of my father's sister. My cousin was a descendant back to Marjory in an unbroken female line of eight generations. My cousin's mitochondrial sample was subjected to a Full Genome Sequencing (FGS) test. This test is still pricey; but lower level tests are not precise enough to return genealogical results that would have been useful in addressing my research question. Since mitochondrial tests for the FGS level are just coming on the market the databases of tested individuals are still very small. However, I was fortunate to have my cousin match exactly two individuals in the database of Family Tree DNA (FTDNA). One of these two matches lives in Finland and the other is believed to be of Finish-American descent.
Now it was time to go back to more traditional family history research. I leaned that at the time of the colonization of New Sweden in the 17th Century, Sweden included most of what is now Finland. In addition there was an enclave of ethnic Finns in central Finland. There was even a settlement in New Sweden at one time which was called Finland. By combining traditional family history research with targeted DNA testing, I learned something about my family that I had previously been unable to unravel. I am still exploring how a surname like Owens got to the colony of New Sweden. My theory for now is that it was originally something slightly different that got anglicized into Owens on this side of the Atlantic. So many genealogical hypotheses can be tested by ingeniously choosing the right relative or relatives to swab their cheeks or spit into sample tubes.