Daniel wrote: “But I heard something about Angels who are able to use a real human physical body sometimes to communicate with us.”
– Not in Buddha Dhamma.
Spontaneous birth of a human refers to the birth of a baby instantaneously, without starting with a zygote. Information on the zygote at, “Buddhist Explanations of Conception, Abortion, and Contraception,” one of the posts in the “Origin of Life” series.
– That happened at least once or twice during the time of the Buddha. I don’t remember the sutta. But there are no records of such birth in modern times.
– However, that is how the first set of human gandhabbas get hold of a “manussa kaya” or a “physical human body” after a human population is wiped out due to a natural disaster over a large region. Once enough humans are born in that geographic region, they multiply via the normal mode (womb-born.)
P.S. This is the solution to the “chicken and egg problem” discussed in many discussion forums. The question there is “which came first, the chicken or the egg”? The answer is that chicken came first via such “opapatika” or instantaneous births.