Sunday, October 3, 2010
So That's Why We Do It
The commentary between Old Baguette and I in the previous post (See Have Enough, Comments) got me to thinking of the infinitesimal chance of our personal existence. There is nothing particularly remarkable about someone existing in a generic sense. Well actually it is incredible that anything exists, and when you think that elements of that existence can develop into intelligent purposeful life is extremely incredible. That said, we have to start some where, so let’s take the fact that the universe and human beings exist for granted. So if we take human existence for granted, we can also take the fact that they are going to have children for granted. So there is nothing particularly amazing about people as a class of objects existing. But what are the chances that the particular you reading this and the particular I writing this exist? One out of what?
A coin toss is 1 out of two. Heads or tails. That can be expressed as a fraction ½. Divide it out and multiply by 100 and you get a percentage answer that there is a 50% chance of a coin toss being heads or tails. So what is the chance of you being you. I tried to look this up on the Internet. Surely some one has figured it out. Well I didn’t find a definitive answer. Most of what I found was philosophical crap ranging from 100% to zero. Some believe that the universe is a deterministic machine and that your chance is 100%. Personally I don’t believe that but I can’t disprove it. On the face of things, it seems that there is a hell of lot of mechanisms of chance operating in the universe. If it is deterministic, why all this baggage for chance? Is it there just to entertain us? If I am going to exist anyhow why do I need two parents? Why did my father produce upward of half a billion sperm cells for a single mating that may or may not work. Although, I don’t subscribe to determinism, there are a lot of smart people who do, so we could stop here and say, you have a 100% chance of existing because the universe can only unwind one way. But for us dumber folk who like to dabble in mystery, that is not a very satisfying answer.
There are a number of ways to look at this. If we only look at our specific parents, according to Wikipedia, one couple can produce 309x10 raised to the 24th power of genetically different zygotes. That fraction is 1/309000000000000000000000000. When you divide a small number by a really big number the answer while not zero per se, approaches zero. The percentage works out to 3.24 with 25 zeros preceding the three. Rather small. And that is just for your particular parents. Now to further throw some chance in the game, what is the chance of your specific father mating with your specific mother? I don’t have clue but it is small. Then you can go back and start considering that if something happened slightly differently in your particular ancestral history, you would not be here. So what is the chance of that? I have no idea but it is huge, making the chance of you small. Here is a site where they tried to figure that out for 250 years backward and 1 million years backward.
Chances of You Existing
Going back 250 years, your particular chance is 1 in 6 x 10 raised to the 100th power.
Looking back only 1 million years ago, you have a 1 in 1.8 x 10 raised to the 403167th power chance that you exist.
I ain’t smart enough to vouch for these numbers so take them or leave them. Of course your genetic makeup does not stop at 250 years or 1 million years backward, so the real denominator is huge by comparison. Percentage wise, it approaches zero, and that is about all that you can say for it. Yet here you are reading this and wondering what I have been smoking.
The absurdity of sex has always amazed me. I have never quite recovered from the shock of those stories I heard back in the 50s—you know, the ones about a game that grownups play where they take off all their clothes and the man sticks his…well you know--were true. It was one thing to believe that grownups played some dirty little game. There could be something to that…especially if you looked at the covers of the paperback books sold in the drugstores at the time. But the notion that this is where babies came from was totally ridiculous. The stork brought babies, and none of us kids believed these nasty rumors. Our parents didn’t do that sort of thing. The fact that I lived through the birth rate of the 50s and didn’t seem to notice the unusual rate that women seemed to gain and lose weight about the belly seems quite remarkable to me now.
Through official parental and educational instruction, I could to this day still believe that the stork brings babies. Neither parent ever explained the birds and bees to me, and while I learned of sexual reproduction in biology class in 10 th grade, it was something very theoretical, genes and chromosones and the likes. How the genes got together and even how the baby was born was left to the imagination. The sperm cell magically got to the ovum, fertilized it, and the embryo embedded to the womb, end of discussion. Womb and gonads were the only parts discussed. It all could have happened in some stork nest located God knows where. Amazing! So I learned all the other stuff on my own, first through the talk on the street and later with books. So here I am at the age of 61 and still in awe of it all. Somewhere I read that sex is God’s joke on mankind. I believe it.
In the process of researching our chances of existing, I read a good bit about the fertilization process. It is quite fascinating. Human fertility is rather poor, 1 in 100. That means that 99 times out of 100 tries is not going to result in a pregnancy on the average. With such a poor record, one is tempted to ask why. Well the overall purpose of sex is of course reproduction, the continuation of the species, but the immediate purpose of sex in humans is to pair bond. Human children are extremely difficult to raise, and they need care for a very long time. It is an evolutionary advantage to have a father around to help raise the children. So sex is a lot of fun but rather inefficient because nature is trying to get the pair bonded before it is time to change diapers.
It is interesting to consider the challenges of sperm. First they are dumped into a hostile environment. The natural acidity of the female tract is deleterious to the sperm cells. The eventual winner of the race has to be close to os, the opening of the cervix, and it must somehow manage to get through the mucous plug in the os. It then has to swim the length of a pear, through the womb, and choose the correct fallopian tube. If the woman is not ovulating, there is no correct tube and all is for naught. If she is ovulating, and it chooses the right tube, it still has the problem of finding the ovum within the ampulla of the fallopian tube. If it finds the ovum, it has to be the first to penetrate the ovum’s outer cell wall by applying an enzyme to dissolve a hole in the membrane. If the enzyme runs out before it breaks through, it will not succeed in fertilizing the cell. There is some thought that the first to make it only weaken the walls for its brothers, that the successful sperm got through a weak spot created by one of the earlier arrivals. When one sperm has breached the wall, the cell membrane must become impervious to other sperm. However, the challenge is not over yet. The mixing of the genes from both parents and some very complicated initial cell division must take place successfully and then the embryo must get out of the fallopian tube and embed in the uterine wall. All of these processes are subject to failure.
When you consider the hurtles, you begin to understand the need for the prodigious numbers of sperm cells and yet most of the time they fail. They fail quite intentionally, with the hope that the man you may some day come to call Dad will helplessly and irrevocably fall in love with the woman that you will call Mom, and she will love him, and by the time you come along they will both love you. As they should for you are rarer than the Hope Diamond.
There is an entertaining simulation of the sperm’s epic journey on YouTube. Do your self a favor and don’t turn your speakers on, the music sucks and there is no narration.
YouTube Human Fertilization
Edit June 4, 2011: I just listened to a RadioLab podcast on sperm that shed some additional light on reproduction. In one segment, the show speaks with Dr. Joanna Ellington on sperm and apparently human conception is not quite the dismal process destined for failure that I would have you believe. The mucus plug in the cervix contains fibers that under normal circumstance are randomly matted and tend to block sperm. However during ovulation, the fibers align axially making a pathway through the cervix. There are internal signals (I would assume bio-chemical) telling the sperm which fallopian tube to swim toward. Also Ellington states that the fallopian tube is a sperm friendly place that will generate sugars to nurture sperm for up to week waiting for an egg to appear. The show is about an hour and you can either listen to it or download it as an MP3 for free at the site below:
RadioLab, 2008/dec/01/ Season 5 Episode 2 "Sperm"
A couple of questions come to mind. Does the woman have any control over the sperm aiding functions noted above. Are they simply functions of ovulation, or is there a psychological component that would aid or inhibit these responses? Considering this built in help, why does human fertility remain such an inefficient process compared to other species?
Ellington is the co-founder of INGfertility which produces "fertility friendly" personal lubricants for couples trying to conceive. You can read more about Ellington's research here:
PreSeed.Com, Press Releases
EDIT 3-3-2013: I have received yet further information that babies actually come from outer space:
I am not sure how to figure the odds on this one.
University of New Mexico, Sperm on an Egg
Wikipedia, Sperm Fertilizing an Egg
National Institute of Health, Fertilization in Humans