Are we alone?

"But evidence favoring life’s high probability could exist closer to home. No planet is more Earthlike than Earth itself. If life does pop up readily in Earthlike conditions, then it should have started many times, right here on our own planet. It could be that intermingled among the seething microbes all around us are some that are so biochemically different they could be descended only from a separate origin. You couldn’t tell by looking, only by delving into their molecular innards and finding something weird enough to rule out a common precursor. The discovery of just a single “alien” microbe under our very noses would be enough to conclude that the universe was indeed teeming with life."
Very stimulant conclusion: if life is due to our earth conditions we can expect several births of life on this planet! Isn't it?

http://www.nytimes.com/2013/11/19/opinion/are-we-alone-in-the-universe.html?nl=todaysheadlines&emc=edit_th_20131119