The Genetics Of “Who’s Your Daddy?”

When the headlines behind this story came across my RSS reader the other day, I was gonna file it under my proverbial “Captain Obvious” category. The basic premise is the potential link between last name and Y chromosome type. We already know that in deep ancestries, like among Jewish people, the Cohen Modal Haplotype (CMH) is notably frequent amongst Cohens. Cohens are a lineage of Jews believed to be direct relatives to the Biblical Aaron. They have a relatively strict marital tradition, one where the last name is preserved paternally.

Many other cultures are structured paternally and last names are inherited, for the most part, from the father’s family. Turi King made this otherwise obvious observation and tried to look for similar Y-chromosome haplotypes among two and half thousand men with 500 different last names. She presented her results to the Doctoral Inaugural Lectures being held in the Frank and Katherine May Lecture Theatre, Henry Wellcome Building, University of Leicester last week.

While not as deep as Cohens, there should be a linkage with almost any man’s last name and his Y-chromosome genetics… So long as name changes, adoptions and multiple foundations of the same last name by different individuals (like Smith) haven’t been prevalent. And that’s why I changed my mind about posting this research. King explains,

“The last name Smith is a good example of this as it derives from the occupation of blacksmith so many men could have taken on the last name Smith. This means that instead of just one type of Y chromosome being associated with a last name, many different types of Y chromosomes would be associated with this single last name. On the other hand, for rarer names, there may have been just one founder for the name and potentially all men who bear that last name today would be descended from him and could be connected into one large family tree.”

When King compared the Y-chromosome makeup of non-related individuals limited down to 40 last names, she was able to see that last names like Attenborough and Swindlehurst showed that over 70% of the men shared the same or near identical Y chromosome types whereas last names such as Revis, Wadsworth and Jefferson show more than one group of men sharing common ancestry but unrelated to other groups.

Ultimately, King was able to show between two men that share the same last name, there is a 24% chance of sharing a common ancestor through that name but that this increases to nearly 50% when their last name is rare. For forensic scientists out there, especially forensic anthropologists who regularly deal with skeletal remains, this can be a godsend because a prediction of a male’s last name is potentially possible from DNA alone. Now disclaimer aside, the press release didn’t really mention her methodology, i.e. how many loci she compared. Of course, the more the merrier. Either way, I’m sure many out there will look forward to larger comparisons of last-name to Y-chromosome correlations.

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