Answer:
All eutherians (placental mammals) were born. Human ancestors were primates, and before that, probably metatherian mammals. Before that our ancestors were some sort of proto-mammal, perhaps a reptile-like mammal. Earlier than that, our ancestors were egg laying pelycosaurs, and before that, amphibians. Before that, something very much like the "fishapod" Tiktaalik, and sacropterygian lungfish before that.
What the lungfish evolved from would have been some jawless fish, which evolved from some earlier egg laying vertebrate. Before that, we're pushing into the early Cambrian, and the picture becomes muddled and hazy. It's half a billion years ago, and the fossils have not been exceedingly well preserved from that period of time. I'd like to see what YOU look like half a billion years from now...
At any rate, we date back to some asexually reproducing metazoan (multicellular creature) living in the seas (a marine organism). From mats of symbiotic eukaryotes the picture grows hazier yet. We are clearly related to single celled eukaryotes (nucleated cellular organisms), some sort of protist. These would have all reproduced via fission, as they do today. Sexual dimorphism (two sexes) would, however, be associated with some Cambrian era speciation event. Both plants and animals engage in sex, though even in higher level animals sexual identity is not necessarily permanently fixed.