I propose that all life on earth begins from other life. Do you agree or disagree?
We don't know for sure but I'd guess that there is a high probability that
today with current conditions this is true. Close enough to 100 % that we can call it 'fact' in fact.
You did use "begins" that makes all the difference. As pointed out by others it is clear, whatever you believe, that this can not have held true for all time.