Was discussing over the internet this evening the issue of data degradation of electronically-stored photo files. See for example https://en.wikipedia.org/wiki/Data_degradation

Is DNA any better at storing data? Not hardly. Consider first the spontaneous abortion rate, meaning the failure of a fertilized egg to produce a live birth. Estimates are that the success rate is about 30%, or turned around that 70% of zygotes abort or fail. Some or most of that is due to developmental failure, birth as lottery, birth as slot machine. (We could go to individual senescence and telemeres and so on but let's not, for now.)

In biological systems, errors fuel evolution. Perhaps one day machine code errors will drive machine evolution. Good for us perhaps that we are not there yet.

Back 39 years ago some of the biology of this was made clear to me when I started working with my cousin who had, he believed, a method for separating X-Chromosome bearing from Y-Chromosome bearing spermatozoa.

You had to ask, WHY should there be any substantial difference between X and Y bearing spermatozoa tht would enable them to be separated? Sure, the X Chromosome is bigger than the Y Chromosome, but consider that bovines have 60 chromosomes, 30 being the haploid number. If the X Chromosome is twice the mass or volume of the Y, that is a difference of less than 3% in the volume or mass of the head of the sperm; a difference in streamlining, maybe?. And researchers were reporting a difference in the electrical charge of X-bearing versus Y-bearing spermatozoa. What was up with that?

(Electrical charge was the basis of my cousin's patented separation technique. He was a reproductive physiologist with degrees from Texas A & M, Dr. R. Loy Lawson, and some info about his patent may still be on the internet. He was a good guy, good to me, a hard worker in many fields from general construction and finish carpentry to science, and he has been dead going on 20 years.)

The problem -- and this something I worked out for myself from reading in my cousin's collection of Science magazines and never fully discussed with my cousin, who had a weird metaphysical idea that males and females were opposite throughout life -- is that the spontaneous abortion rate is much higher for male zygotes, embryos, and fetuses than for female. One Science article estimated that in humans 170 males were conceived for every 100 females.

The high rate of spontaneous abortion might be because females have a fully paired -- XX -- genotype while males had NO pairing of the sex chromosomes, leaving males lacking backup genes for any data on either the X or Y chromosome except what might have been swapped around by crossing over. Or it might be because of hormones. Females are biologically the stronger sex.

BUT, despite the high pre-birth attrition of males, at birth the sex ratio is not far from 50:50. (It's about 52:48 in humans in favor of males.)

This means that nature has been compensating for the high pre-birth die-off of males by ensuring many more male conceptions, that nature had been doing what my cousin and others were trying to do, and that was somehow favoring X-Chromosome bearing spermatozoa in the race for conception!

But why would THAT occur? This brings up the Fischer Theory of Sex Ratios, which in a nutshell says that purely as a statistical equilibrium, the sex ratio at birth MUST be about 50:50. Think about a herd of wild horses and what an optimal sex ratio might be and if that could be genetically perpetuated. Why should half the foals born be males when, say, 20% males would be reproductively more efficient? If an 80:20 sex ratio at foaling WERE genetically coded then the first horse that produces more male offspring than 20% has a disproportionally greater impact on the gene pool, and that horse's descendants continue to do so, until the average birth sex ratio approaches 50:50.

Therefore nature genetically adjusts the sex ratio., compensating for male frailty by ensuring more male conceptions.

Posted on June 27, 2018 07:59 AM by thebark