Consanguinity & DNA Probabilities — #Genealogy #DNA #Kinship

by C. Michael Eliasz-Solomon

Stanczyk last wrote a similarly named article, “Genealogy Consanguinity & DNA“, on 25-August-2014. But in the last week, I read two blogs that made me rethink some of the comments that we received to the blog on the probabilities of autosomal DNA (the non Y-DNA and non mt-DNA). I also read a blog once by William Dollarhide that a Family Tree should represent the DNA, the Consanguinity (how much blood shared). Although I respect the tremendous body of work and prolonged expertise of Mr. Dollarhide, my immediate reaction  was, “No, it does NOT”!

So today’s blog is a mash-up of my August 25th blog, two recent blogs I read, and William Dollarhide’s blog article on the Family Tree represents the DNA.

First off, let me state my bias up front, that I believe the Family Tree represents Legally Defined Familial Relationships as held out by the Family Tree’s owner and that copies or derivative versions or edited/annotated versions are NOT valid! There has been a long history from at least the earliest dynasties of the Pharaohs and probably even older than that the “king”, let me gender-neutral the term, the monarch decides who is family and who is erased from family histories and who inherits and who does not inherit. So we see a very early reason why family trees ARE legal based. If the wife of the monarchical family could not produce a LEGAL heir to inherit or continue the dynasty, one was often adopted or perhaps produced with a surrogate spouse. So we also have a new counter argument enter on very early in the history of families … adoptions. The adopted child may or may not possess some consanguineous blood (DNA). It was not unusual for children of siblings to be adopted if they were orphaned. Or perhaps we can view more upheaval from recent times producing ad-hoc adoptions of non-kin. We need not just accept the modern day gay-couples who adopt or couples with fertility issues who perhaps adopt an overseas child , who may or may not share any consanguinity with either parent, but are none-the-less, legal family members of a family and as such should be in the family tree. We can easily recall just the upheaval of World War II where children from Jewish families were often times ad-hoc adopted in order to save the child’s life and perhaps raised to adulthood without the knowledge of their true DNA (until later). There have been many such stories.

DNA was a late 20th century discovery, so before its discovery, there was simply no way of knowing for sure that a baby arriving from its mother’s womb, was the sire of any man in particular. Here, again we find examples of mistakenly assumed child of both parents, has the DNA of the mother, but none of the father. Yet in most cases, the family tree shows the child with the couple who raised the child and were held out to be its parents (legally).

We have also seen people use a last name to pretend or to get others to think they are from a family. I am thinking now of a man who used the Rockerfeller name when he had no consanguinity with the famous family. There have also been people who claim to have been a long-lost member of the executed Romanov family. But these people are not legally related to the more famous families by their covert or overt claims of familial ties. They are not to be represented in any LEGALLY sanctioned family tree of their creation, nor anyone else’s with those famous families. These faux family members could be EXCLUDED on the basis of DNA in all probability.

We come back to the PROBABILITY portion of this article. DNA and what are the probabilities of consanguineous relatives in the autosomal DNA (not in the direct paternal or maternal lines which can be mathematically determined with reasonable accuracy). When I wrote the blog article from August 25th, people began to immediately take issue with the data visualization that I had sourced on the autosomal boxes. For example, should siblings be 50% consanguineous? In most probabilities, yes. Now let me limit probabilities where by the mother and father are both known for certain — otherwise the mathematics goes out the window.

So siblings share 50% correct? What about identical twins? Who may or may not be 100% identical in DNA. What about fraternal twins or any of the other myriad multiples that can be conceived of? Oh, their DNA probabilities are likely much higher than siblings born from separate births, maybe approaching 100% shared DNA. So now the probabilities of consanguinity are skewed for future generations depending on which child you are in direct lineage from.

Autosomal ProbabilitiesWhat is the accepted standard for probabilities? I recently read a blog by Iowa DNA Project. She included a chart from The International Society of Genetic Genealogists. I have included that chart in this article.

The chart answers most of the questions from people on my first blog that I was not able to answer definitively. Notice one caveat to those probabilities !  These are what we can EXPECT as the probabilities for shared consanguinity.

Why are they not guaranteed? Well the first answer occurred to me because of my knowledge of genetic algorithms (and high school science). The first answer is Mutations. Sometimes when the genes copied from one parent or the other, an inexact copy results in the DNA sequence. There are also a few other things that can go wrong in the sequence.

That is perhaps a nice segue to the second blog I read recently, “Why Your DNA Might NOT Match Your Parents“. This article is actually from July 3rd of this year, but which I read last week. What happens when the mother has a rare condition called Chimerism? A short explanation is the mother has two fertilized eggs in her womb, but then one twin fuses to the other and only a single baby develops and is born. In this case, the baby does NOT share DNA with the mother who is in fact the biological mother but technically shares zero consanguinity with the baby. Now Chimerism is rare but since it has happened recently, it is likely it has happened in the past (albeit rarely) of humankind. Well that really screws up the DNA. Now if you were a direct line descendant from a Chimera baby, your DNA does not match the DNA of the rest of the  family. Let that sink in.

Now without even discussing surrogate mothers or other elaborate fertility techniques or even parthenogenesis, I believe I have completely destroyed the William Dollarhide notion of a family tree being a representation of DNA (or consanguinity). I did not even touch upon infidelity, “kings-privilege”, rape/incest/forced insemination or other known or unknown “ad-hoc adoptions” that occur in family trees with/without knowledge of the family members [since DNA and its use is recent and not widely used]. Nor did we discuss legal  dis-owning or disinheritance until this sentence. Those too would impact a family tree.

Perhaps all Family Trees really are Legally Defined Familial Relationships as held out by the family tree owner! Whether we agree or not or whether we know/believe it or not, the long process of DNA replication and historical/legal edicts have irretrievably altered all of our family trees.

The author wishes to include a post-scriptum on his own Legally Defined Familial Relationships (aka my Family Tree). As for my dear wife, Teréza & I, we felt the need to utilize extreme fertility techniques  in our personal life to produce our own biological children. We have also used legal disownments, disinheritance, name changes and an annulment to separate ourselves from others who have sought to make fraudulent claims of familial status … asserted fraudulent relationships in their own utterances:   for purposes of past, present and/or future schemes to possibly gain money from me, my wife, Teréza  or any future estate and/or cause us harm and other damages!

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One Comment to “Consanguinity & DNA Probabilities — #Genealogy #DNA #Kinship”

  1. Thank you for posting about your family tree. I have always maintained that genealogy is more than mere biology, and as time passed, research findings bore this instinct out. Finally, in a recent vindication of events that occurred more than two centuries ago, many years after I was divorced, when my youngest son reached the age of majority, he decided he wanted to legally change his name, and he did: to the maiden name I had legally resumed.

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