Tuesday, October 22, 2013



Natural law is a foundation for the morality of some people, probably both those that are atheists and those that are deeply religious.  For those that are religious and believe that God created the world and is the author of natural law it would seem that they would find evolution an aide if they realized God is the author of evolution.

I recently started thinking about this topic when a friend of my wife was discussing with her the relative contributions of men versus women to genetic flaws found in offspring.  The friend thought women get blamed for the preponderance of genetic flaws such as trisomy 21 which occurs with a higher frequency when the mother is older.  I wasn't too quick to point out that males always pass on flaws of their X-chromosome to their daughters and of their Y-chromosome to their sons.

Of course, mitochondria are another matter since they are only passed on through the mother's egg.  So pick an energetic mother and don't worry about having a lethargic father if you want to have plenty of energy.  But it is not that simple.

From an evolutionary standpoint, in vitro fertilization is a terrible mistake.  Old-fashioned sex is the best way we have to deliver healthy sperm to an egg.  Aging and/or defective sperm may not have the energy to reach the egg and be the first to donate their chromosomes to the egg.  How important that is can be demonstrated by the higher percentage of males conceived.  Carrying a large X-chromosome must slow them somewhat compared to carrying a small Y-chromosome.  Not all deleterious genes will be expressed in egg or sperm but those that are can perhaps be selected out by the competition of sperm to reach and fertilize the egg.  The sperm also have to have some teamwork by helping to disperse some of the cells surrounding the egg so one can fertilize the egg and immediately cause the fertilization membrane to form and prevent other sperm from entering.  It makes it seem like males participate in team sports from day 1.

So it would seem that the fertility clinics may be unwittingly defeating the natural selection that helps maintain the fertility of the human population.

Who wins the battle of the sexes in a genetic sense?  I have no idea, it seems pretty even to me.  But sex-linked recessive genes behave as dominate genes when in a male.  For that reason red-green color deficiency in vision is many times more common in men than in women.

Joe Engemann     October 22, 2013

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