Because the carnal mind is enmity against God... Romans 8:7
"Aristotle proposed an early version of spontaneous generation, and 
it
remained popular until the nineteenth century.
At that time,
experiments by Louis Pasteur and others proved the fundamental law of
modern biology, biogenesis (life only comes from life). Support for
spontaneous generation gradually lost popularity. Well, sort of lost
popularity.
Interestingly, toward the end of that same biology course we
were taught that life may have originally arisen by spontaneous
generation.
Confused?
Supposedly, life could have arisen in the distant
past under unique conditions, unlike those found on earth today.
In
other words, life will not spontaneously form today, but it must have
under unknown conditions earlier in earth’s history.