How Amazingly Unlikely Is Your Birth
Septmeber 2019
You may recognise the title of this article from Eric Idle’s “Galaxy Song”. But have you ever wondered about exactly how unlikely it is that you have been born? As human beings we come from a union of an egg being fertilised by a sperm. So what are the chances of this happening?
Let’s start with eggs. At birth, each baby girl is born with all her eggs approximately 1-2 million. About 11,000 of these die every month. By puberty, a woman's egg count might be 1 million; at 25, maybe 300,000. Once she starts her periods, 1 egg develops and is released during each menstrual cycle. Approximately 1,000 eggs are destined to simply die each month and, as eggs are a non-renewable resource, her total number keeps going down as time goes by.
Of her individual original total of 1-2 million eggs, only 300 to 400 will be ovulated during a woman's reproductive lifetime.
Now let’s look at sperm. A man may ejaculate 40 million to 200 million sperm during sex with a woman. These start swimming upstream toward the fallopian tubes on their mission to fertilize an egg. Fast-swimming sperm can reach the egg in a half an hour, while others may take days. The sperm can live up to 48-72 hours.
So how many eggs and sperms come together? For simplicity, let’s restrict ourselves to considering monogamous relations between men and women. Statistically the size of an average family differs around the world. In Africa the average woman has 5 children whereas in the UK it is just over 2. So the average British woman will have 2 children resulting from 300 - 400 ovulated eggs which is a 1 in 150 – 200 chance. However, remember this is using the total number of ovulated eggs out of a total number of 1-2 million eggs. Let’s take the maximum totals of 400 ovulated eggs being produced from 2 million eggs. That’s a 1 in 5,000 chance of an egg ovulating then a 1 in 200 chance of that egg being fertilised.
When you take sperm into account then the numbers really take off. The chances of 1 sperm fertilising an egg is 1 in 40 – 200 million. And that is just in 1 shot from the man if the woman happens to be fertile at that time. You also have to take into account the numbers of sperm that go nowhere when a woman is not fertile or when a couple use a condom. Plus we can’t ignore the fact that every ejaculation from a man does not necessarily end up in a woman. The chances of any particular sperm from the average man finding an egg partner are not great.
So think of all the countless billions upon billions of non-people who have never existed because their eggs were released during a woman’s period and never fertilised or lost during the natural course of a woman’s life or because their sperm did not win the race to the egg or came out in a wet dream or any of the other methods of relief employed by men down the years.
When you think of it like that then each one of us really is one of the few, the happy, lucky few!
So as Eric Idle sings in “The Galaxy Song”:
“Remember when you’re feeling very small and insecure,
How amazingly unlikely is your birth!”
You can hear this at https://www.youtube.com/watch?v=vIy76M-4txo
Below are 7 fascinating facts and 2 links to another Monty Python song.
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Most cells aren’t visible to the naked eye: you need a microscope to see them. The human egg cell is an exception. It’s actually the biggest cell in the body and can be seen without a microscope. That’s pretty impressive especially when compared to spermatozoa which you do need a microscope to see.
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Because each woman is born with all her eggs, this means that your eggs were once inside your mother when you were a foetus in her womb. That means your mother carried the egg cells which may one day be fertilized and grow into her own grandchild!
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Most women release an egg cell every cycle. This is called ovulation. Some women can release two egg cells per cycle. This can result in the conception of paternal or fraternal twins. Identical twins are made when the fertilized egg cell divides in two. Identical twins grow in the same amniotic sack and, unlike fraternal twins, are genetically the same.
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In human pregnancy, a developing foetus is considered as an embryo until the ninth week, fertilization age, or eleventh-week, gestational age. After this time the embryo is referred to as a foetus.
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Birth is a high-risk affair for mammals, in general, but it’s especially so for humans. The constraints of the narrow human pelvis, thought to be an evolutionary trade-off of walking on two legs, combined with the exceptionally large heads of human babies, makes human birth especially difficult, and therefore dangerous, compared to other animals.
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Mr and Mrs Feodore Vassilyev (his first wife) are alleged to hold the record for the most children a couple has parented. She gave birth to a total of 69 children – sixteen pairs of twins, seven sets of triplets and four sets of quadruplets – between 1725 and 1765, a total of 27 births. 67 of the 69 children were said to have survived infancy. Allegedly Vassilyev also had six sets of twins and two sets of triplets with a second wife, for another 18 children in eight births; he fathered a total of 87 children. The claim is disputed.
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An old joke. Question - what do you call people who use the rhythm method of contraception? Answer - Parents.
And finally, here are the links to 2 versions of the “Every sperm is scared” song from Monty Python’s “Meaning of Life” which is well worth watching if you haven't done so already.
https://www.youtube.com/watch?v=fUspLVStPbk (This lasts 4:16)
https://www.youtube.com/watch?v=bzVHjg3AqIQ (Longer copy with preamble – 6:50).
Brian Madican
Sept 2019
