Final answer:
There are slightly more male conceptions than female conceptions mostly due to a random chance during fertilization, where sperm with either an X or Y chromosome may fertilize an egg. Sex differentiation then takes place, but the initial conception process does not significantly favor male over female embryos.
Step-by-step explanation:
The idea that there are many more male conceptions than female conceptions is that it is a random occurrence. Neither male fetuses being more resilient, Y-chromosome-bearing sperm swimming faster, nor environmental factors give a clear advantage for male conceptions to occur more frequently than females. While the initial conception process is random, other biological and environmental factors may influence the survival rate of the embryos later in development.
Every pregnancy starts at conception, where an egg is fertilized by a sperm containing either an X or a Y chromosome. A Y chromosome leads to a male offspring, while an X chromosome results in a female offspring. This process is essentially random, as a sperm carrying either chromosome has an equal chance of fertilizing an egg. After fertilization, sex differentiation occurs, initiated by the gene SRY on the Y chromosome, which triggers development into a male fetus. Without this gene, the default developmental pathway is female.
Overall, gender is determined at conception, and while males may be conceived at a slightly higher rate than females, the differences in ratios may change by birth due to higher mortality rates in male fetuses and infants. The persistent myth that Y-chromosome sperm swim faster has been debunked, and there is no strong evidence that environmental factors favor male embryos during conception. As such, the more numerous male conceptions should be considered a random event, influenced by subsequent biological and environmental factors post-conception.