Against All Odds: The Astonishing Probability That You Exist What are the odds you exist? Every ejaculation contains about 200 million sperm, but only one fertilizes the egg. Your exact sperm had to be that one, roughly 1 in 200 million. Your mother’s egg was one of about 400,000, the estimated number of eggs a female is born with, and only one is released in each menstrual cycle. The chance of that exact egg being released is about 1 in 400,000. Multiply these together and the odds of that precise sperm meeting that precise egg are about 1 in 80 quadrillion. Not every fertilized egg survives. Historically, about one in three pregnancies failed. Surviving in the womb reduces the odds slightly to 1 in 120 quadrillion. Both parents had to survive childhood, avoid deadly accidents or disease, and meet at the right time. If we estimate this at 1 in 100 for each parent, the odds drop to 1 in 1.2 quintillion. Every ancestor over thousands of generations had to survive and reproduce. If we assume a 50 percent survival rate per generation over just ten generations, the cumulative probability is 1 in 1.2 sextillion. Stretch this back hundreds of generations and factor in early humans surviving predators, famine, disease, and harsh climates, and the odds become effectively unimaginable. Even beyond Earth, the odds shrink further. Scientists estimate that only about 1 in 5 stars has a planet in the habitable Goldilocks zone, where conditions are just right for life as we know it. You also had to be born on such a planet at the right time in its history, making your existence astronomically rare. Combine all of these improbable events, fertilization, survival, reproduction, and being on a life-supporting planet, and the odds of you being alive right now are estimated at roughly 1 in 10 to the power of 2.5 million. Imagine covering the Earth with lottery tickets stacked a mile high and picking the winning ticket trillions of times in a row. #Science #America #USA #News