(Your Parents) Now let’s say the chances of them actually talking to one another is one in 10. And the chances of that turning into another meeting is about one in 10 also. And the chances of that turning into a long-term relationship is also one in 10. And the chances of that lasting long enough to result in offspring is one in 2. So the probability of your parents’ chance meeting resulting in kids is about 1 in 2000.
Probability of same boy knocking up same girl: 1 in 2000.
So the combined probability is already around 1 in 40 million — long but not insurmountable odds. Now things start getting interesting. Why? Because we’re about to deal with eggs and sperm, which come in large numbers.
Each sperm and each egg is genetically unique because of the process of meiosis; you are the result of the fusion of one particular egg with one particular sperm. A fertile woman has 100,000 viable eggs on average. A man will produce about 12 trillion sperm over the course of his reproductive lifetime. Let’s say a third of those (4 trillion) are relevant to our calculation, since the sperm created after your mom hits menopause don’t count. So the probability of that one sperm with half your name on it hitting that one egg with the other half of your name on it is
1/(100,000)(4 trillion)= 1/(105)(4×1012)= 1 in 4 x 1017, or one in 400 quadrillion.
Probability of right sperm meeting right egg: 1 in 400 quadrillion.
(your odds are better, hitting the lottery)
Lets face it, that makes you and me, walking miracles.
You are a miracle