Life on earth is likely evolved from organic bubble (or protocell) formed from natural catalyst and use energy from hydrothermal vent. DNA is believed to originated from self-replicated polymer allowing advantage in forming better bubble layer. With the long process of natural selection of part, the protocell transformed to single cell organism and start the life on earth.
A rose can begin it's life in a few different ways. It can begin it's life as a seed or as a rose branch.
in water
Immediately, now that I have enriched your life by answering your question.
puberty
As the seed that you eat
an egg
yes there is aliens are the only ones who can begin life there.
Stars begin their lives as clouds of gas and space dust.
Africa is supposed to be the cradle for all life, theoretically.
zygote
About 3500 mya.
As a single cell.