9. DNA tests have revealed that all possible biological descendants only come from Emma.
In the modern age, we have more scientific tools at our disposal. Since the early 2000s, DNA kits have been available to the public and been used in paternity cases. When father, mother, and child are all living, scientists can determine with accuracy DNA connections. When the supposed parents and offspring are dead, the task is more difficult.
Dr. Ugo A. Perego, a geneticist, began working on Joseph Smith’s genealogy. By 2010, he had used genetic testing to rule out the Prophet’s parentage of 7 boys that were born to legally married women to whom he was sealed.
There was one potential offspring that he could not rule out: Josephine Lyon. Because she was female and didn’t possess a Y chromosome, the same DNA tests wouldn’t work to identify her father.
One of the claimed descendents of Joseph Smith through a plural wife was Josephine Rosetta Lyon. She signed a statement in 1915 which includes the following:
Just prior to my mothers death in 1882 she called me to her bedside and told me that her days on earth were about numbered and before she passed away from mortality she desired to tell me something she had kept as an entire secret from me and from others until no but which she now desired to communicate to me. She then told me that I was the daughter of the Prophet Joseph Smith, she having been sealed to the Prophet at the time that her husband Mr. Lyon had was out of fellowship with the Church. (Hales, Joseph Smith’s Polygamy: Vol. 1: History, p. 350)Even though her mother suggested that she should consider herself a daughter of Joseph Smith, that doesn't mean she was biologically related to Joseph.
As Rex E. Cooper observed, “the statement is unclear about what it meant to be a ‘daughter of Joseph Smith.’ For example, because of his mother’s matrimonial sealing to Joseph Smith, Heber J. Grant was regarded as a ‘son of Joseph Smith’ even though he was born twelve years after the prophet’s death.”(Promises Made to the Fathers: Mormon Covenant Organization, p. 144, footnote 1—cited by Hales, Joseph Smith’s Polygamy: Vol. 1: History, p. 351)In June 2015, the descendants of Josephine Lyon contacted Dr. Perego and requested that he once again test for paternity using advanced technology. With their cooperation, he again oversaw testing. This time the results were conclusive: Joseph Smith was not the father of Josephine. Windsor Lyon, her mother’s legal husband, was her father.