Is it possible there were multiple origins of life? And, if so, why did the one which became the common ancestor between all organisms prevail?
It is interesting that all forms of life use the same genetic code. The nucleotides composing DNA and RNA are universal. Eric Lander, geneticist from Harvard/MIT cites this as evidence for evolution from a single ancestor. I think your instructor may be saying that it's possible alternative adaptations for initiation of life may have occured and perhaps not worked out. They become just another of nature's experiments that ended in extinction. I seem to recall reading somewhere all but 2% of species have ended in extinction.