Genetic Identity & Chimeras

Details of bony structures in 14-week-old fetus from an ultrasound equipment manufacturer.

If you’ve followed this blog for long, you know I am pro-life, both on religious grounds and on scientific grounds. In a recent discussion on Twitter, I made a point I have made before, that the fetus cannot be a part of the mother’s body (as many pro-abortion advocates say), partly because the fetus has different DNA from the mother. Later in the discussion, an objection was raised to this point that I hadn’t heard before, so let’s work through that today.

For those who may have been living under a rock the last 60+ years, DNA is the complex molecule Deoxyribonucleic Acid found in every living cell that stores the “blueprint” for that person. First discovered in 1869, it’s structure was finally determined in 1953, and the staggering informational content fully mapped in 2003. After that slow start, our knowledge about DNA and uses for that knowledge have increased dramatically over the years. Some of the most common uses of DNA testing include determining parentage, convicting guilty criminals (or exonerating those wrongly convicted), and identifying partial or unrecognizable remains. Essentially, these examples use DNA to verify the unique identity of individual persons. Now combine that with the well-established fact that by the time fertilization is complete (within 24 hours of the joining of sperm and oocyte), and while still only a single cell, a developing baby has DNA distinct from either parent. The obvious conclusion, biologically, is that this rapidly developing organism is not the same organism as the mother.

Now, the objection raised was that unique DNA doesn’t determine how many lives are present because of the existence of chimeras. What’s that, you ask? A chimera, outside of the mythological monster from which the name is drawn, is an organism with two (or more) distinct sets of DNA. Though not “new” in terms of existence, the first confirmation of a natural human chimera was in 1953 when a woman in England donated blood and it was found to contain two different blood types in one sample. As our knowledge of genetics has grown and DNA testing has become more commonplace, so too has observance of this phenomenon. for instance, a woman needed a kidney transplant in 1998, but when her 3 sons were tested as potential donors, 2 of them were determined, based on DNA, not to be her biological sons, even though she had given birth to them. Then in 2003, a woman in Washington filed for welfare benefits for her children and was denied, with accusations of welfare fraud pending, because her 2 children were determined not to be hers. A 3rd child was born while this was being investigated, so that birth and an immediate DNA test of both mother and child were witnessed by an officer of the state. Again, the DNA test showed different parentage for the child just born. What happened in each of these cases? Each of these 3 women had been twins. The Englishwoman in 1953 had a twin brother who had died shortly after birth. Cells had been shared between the two early in the pregnancy. The other 2 women were both the result of fused embryos, or a “vanishing twin”. Two oocytes had been fertilized by two sperm, resulting in twin zygotes. Early in the pregnancy, however, the two zygotes merged into one. Because they were separate zygotes, they each had different DNA. However, because this occurs very early in development, the zygote is still a collection of totipotent cells (meaning each cell at this stage can still become any cell in the human body, i.e. they have not differentiated into their separate lines of specialized cells for organ generation). When the twin zygotes (call them A & B) fused together, some of the cell from twin A went on to form various body parts like the skin cells inside the cheek where DNA samples are often taken. Cells from twin B went on to form other body parts such as the ovaries that would be responsible for producing children “not her own”. A third scenario, Fetal Microchimerism, or FMc, is much more common and is when cells from the blood of the fetus and/or mother get through the placental barrier to reside in the other person. Cells from their children have been found in the bodies of autopsied women many years after their pregnancies.

Based on these observed cases, we know that a person can have multiple DNA. But does the existence of chimeras refute the idea that the developing baby is a unique individual distinct from the mother? I don’t think so. After all, when a patient receives an organ transplant, the donated organ will have the donor’s DNA rather than that of the recipient; but nobody considers the donor and recipient to be part of the same body. Furthermore, even though the person may have 2 sets of DNA in their body, the transplanted organ is only one organ, and cannot become anything more. A zygote, on the other hand, is capable of developing into a mature human, and is, in fact, directing much of the pregnancy. The case of cells passing between twins in utero, as in the 1953 English case, is really no different than the case of organ donation between adults. The case of fused zygotes is more extreme in that all of the “donor” has been passed to the recipient, but the concept of a donor providing some portion of a recipient’s organs still applies. Because the transfer of genetic information occurs at such an early stage, it’s impossible to know which organs formed from donor and which from recipient without some kind of comprehensive test that is not practical at this point, but it’s important to remember that neither zygote had the same DNA as the mother, so the resulting chimera is still not part of the mother’s body no matter how you look at it. As far as fetal microchimerism, we are only talking about a few individual cells from a genetically unique human (i.e. the baby) passing through the barrier that normally separates the baby’s blood from the mother’s, and residing in the body of another genetically unique human (i.e. the mother). The fact that a few of the baby’s cells migrate into the mother’s body (and vice versa) no more make the baby part of her body than an organ donor’s cells inside a recipient’s body makes the donor part of the recipient.

Does the chimeric objection succeed? No. Even with individual persons not necessarily being limited to only one DNA in their body, the baby is at all stages of development a separate, self-contained organism temporarily residing in the mother for nourishment and protective environment, and not a “part” of her that just has different DNA. All cases of chimerism, both natural and artificially induced, come about from the involvement to one degree or another of a second, genetically distinct organism. The different DNA confirms this and actually bolsters our understanding of a baby as a genetically unique individual from conception.


Further reading: “The Human Chimera: Legal Problems Arising From Individuals with Multiple Types of DNA“, by Robert Russell Granzen, Seton Hall Law School, 2014, was a thorough and interesting read on the matter.

On Turning Arguments into Discussions

“Endless Debate”, by Norman Rockwell

I had an interesting discussion with several people on Twitter last week regarding the topic of abortion,  and came away with a few observations I’d like to share today.

  • The danger of echo chambers. This discussion took place on the Twitter feed of an abortionist who proudly performs late-term abortions. It became quickly apparent that the feed was basically an echo chamber for those who agreed with her to reinforce each other’s beliefs in the rightness of their cause. There is a time and place for mutual encouragement and support, but like a closed-off room grown stagnant, our minds atrophy when isolated from opposing views. For even exposure to mistaken views or outright malicious falsehoods can still benefit us by forcing us to think through what we believe, why we believe it, and, ultimately, if our reasons are adequately justified. As the apostle Paul said, “Examine everything carefully; hold fast to that which is good” [1Th 5:21]. Being in an echo chamber had led several of her followers to fall for some very bad arguments. On the other hand, as a Christian, I have access to the only transcendent source of truth – God – in the forms of His written word, the Bible, and the guidance of His Holy Spirit. What a blessing! And getting support and encouragement from fellow believers drawing from that deep well of truth is a great thing. But that can turn into an unhealthy echo chamber for a Christian when it a) ends up only encouraging in spite of error that really needs correcting, or b) leads to being disconnected from the world Jesus has commissioned us to be ambassadors to [2Cor 5:20]. As an example, an American who never learned about Chinese culture would likely not be an effective ambassador to China. He would need to both represent his own country well and understand his host country enough to communicate with them clearly. Similarly, we are called to be “in the world, but not of the world” [Jn 17:14-18]. The Christian must be different, but who will ever know Christ made a difference in our lives if we stay isolated in a little Christian bubble [Mt 5:14-16]? So we need to be willing to engage with opposing views, but always with gentleness and respect [1Pe 3:15], speaking the truth in love [Eph 4:15].
  • The difference between monologue and dialogue. There were some initial insults and somewhat immature replies to my bringing science to bear on the subject of abortion, and my addressing biologically incorrect arguments seemed to be falling on deaf ears. Eventually, however, someone came forward willing to engage in serious dialogue. He wanted sources for what I was saying so he could verify them himself, so I gladly gave him quotes & references from different embryology textbooks. A civil, thoughtful discussion ensued – on Twitter of all places! Now, I’ve learned many things over the years from presentations that were essentially monologues, such as seminars without Q&A, or recorded webinars, and so forth; but dialogue is critical in discussing controversial topics. A person will only learn from a monologue if they go in willing to listen, and open to absorbing new knowledge (like a seminar I’ve paid to attend). But in a hostile situation, the other person is already defensive at having their views challenged, and dialogue with the person, instead of a monologue directed at them, is really the only hope for changing their mind.
  • The persistence of presuppositions. What was intriguing about the discussion was the repeated assumption that my objections were religious in nature, even though I’d never mentioned anything related to religion (of any kind) in my comments. It took a while to finally convey the point that a response from a user with the name “Well-Designed Faith” didn’t mean that every statement I made would be a religious statement, and that while I could make a religious objection to abortion, I hadn’t, and they would still need to deal with the scientific objections I had made. So why did that reaction happen in the first place, and why did it continue? I can’t get into anyone else’s head to determine their thought process, but it appears that those commenters had some unjustified presuppositions that anything a Christian said was related to Christianity and could be safely ignored. That is nothing more than the genetic fallacy – that the origin (or genesis) of an idea can determine its truth. For instance, the idea that a man can’t speak about abortion only looks at the origin of a message rather than the content of the message, which stands or falls on its own merits, regardless of who says it. In fact, that line of faulty pro-abortion reasoning actually undercuts the 1973 Roe v. Wade Supreme Court decision that was judged entirely by … men. Likewise, while I am a Christian, my objection that the unborn baby is biologically not a part of the mother’s body is well-grounded medically, and is an objection raised by both Christian and atheist pro-lifers (yes, there are atheist pro-lifers…). So, just because a Christian raises the objection, that doesn’t mean one can dismiss it just because one has a low opinion of Christians. Similarly, the Christian can’t dismiss arguments without weighing them, or just because of who made them.

Just a few observations this week about being good ambassadors, as I learn “on the job” to be a better one myself. So listen to what’s out there; it doesn’t help to answer the question nobody’s asking, and not deal with the issues shaping our world. Talk with people instead at them, and remember that they’re not just icons on screen, but real people, created in God’s image (even if they reject that truth). When it seems like you’re just talking past each other, step back and look for presuppositions (on both sides) that may be preventing you and them from understanding what the other is saying. And, as Greg Koukl, that master ambassador for Christ, would say, “Get out there, and give ’em Heaven!”