Predestination (2014) is a well-crafted time travel story, which I found quite remarkably consistent.
There was however one point in the plot that tickled the suspension of my disbelief.
The movie tells of the birth of a baby, whose parents are Jane, and
Both parents respective genetic materials must be
the same, because Jane and John are the same individual, a few years (and 1 time travel) apart.
The movie suggests that the baby was created through classical human fertilization.
As this article about genes inheritance recalls, human gametes (ovum and sperm) contain half the genetic material of the parent ; and all gametes produced are genetically different from each other.
In other words gametes contain a random half of the parent's genetic material (which is why non-twin biological siblings are not genetically identical).
However the movie also reveals that the baby is
the same individual as Jane (and John).
For this to be consistent, it would mean that
the combination of the ovum provided by Jane, and the sperm provided by John, results in the exact same genome as that of Jane/John.
I estimate that this has a probability of happening of less than 0.00000000000142%, arguably smaller than the probability of time travel to ever become possible...
Were there hints or assumptions in the story explaining the occurrence of this improbable event?