Sunday, January 25, 2015
The Key to Healthy Children for Incestuous Couples
The traditional argument against close relatives having children (besides "Ew, yuck!") is that they risk a higher rate of genetic disease. Now, I'm not going to get into the old debate over whether a 2% or 4% or 8% increase in disease warrants such a strong reaction. In fact, I'm writing to challenge a basic assumption by both sides in this argument: that the parents' genes are even the primary problem here; as well as to show that one day soon, we might be able to eliminate most of these risks.
There's a term scientists have, a catchall phrase, for all the detrimental effects of close genetic mating on a population: inbreeding depression. (It's the fitness of the population that's depressed by generations of interbreeding, hence the name.) Inbreeding depression does not occur in the ways or at the rates scientists would expect, if bad genes were the only real cause. Environment can make the difference between consanguineous mating hurting or helping the population, and some species don't even seem to be affected by interbreeding. (Skip to 2:44 if the link doesn't do that for you.)
The fact is, we're all carrying around junk in our genomes that could cripple us, but it never gets turned on. After all, bacteria are cloning themselves, and they seem to do fine, and yet we mammals have increased problems having children with our twins? Doesn’t that seem odd? Well, it is odd.
Where do the increased problems come from, then? The answer: epigenetics. Recently, scientists have realized that which combinations of genes are turned on when, is just as important as which genes you actually have. They've discovered that environmental factors over your lifetime chemically alter your DNA, changing the way it's expressed. These changes over your lifetime can control your weight, your rate of cancer, and more, and you can even pass these changes on to your children. This allows species to evolve quickly without having to even change their genes.
The most powerful epigenetic process is called DNA methylation. Methyl compounds bind to your DNA, inhibiting certain genes. If you have too little methylation, harmful genes accumulated over the life of our species can get turned on, causing diseases such as cancer. If you have too much methylation, many important genes can fail to turn on, and your cells won't properly coordinate or function, leading to developmental problems or miscarriage.
But this all comes with some miraculous discoveries! Recently, several research papers have shown that many of the bad side effects of consanguineous mating that we previously thought were caused by bad shared genes (a.k.a. inbreeding depression), aren't caused by bad genes at all! They're caused by epigenetics, specifically too much methylation during the embryo's development.
But this is actually great news, because the epigenome is easier to modify than the genome. There's something even more amazing that came out of that first paper: the way they tested their methylation hypothesis was by curing their experimental group of inbreeding depression! (The test group members were bred with themselves, which is as close genetically as you can get.) Yes, we might have the technology now to eliminate most of the extra risks consanguinamorous couples face when having children! Unfortunately, the treatment's not commercially available - epigenetics is too new a field. However, it is something we can look forward to.
Because your epigenome changes over your life, and affects the epigenome of your children, there should be steps you can take now to decrease the likelihood of problems your children would face. (This goes for all couples, not just the consanguinamorous.) Lifestyle choices, like chemical exposure, diet, and exercise affect your epigenome. Unfortunately, there's not enough research on the epigenetics of consanguineous mating for me to really tell you what you would have to do. If you're curious, consult a doctor, perhaps they have some more insight than I can give on specific actions you can take.
Edit: Further research provides some practical advice!