Evolution of life might not be easy but on the space/time magnitude we are considering it is "likely" IMO.Two things. First, I don't think I ignore the time dimension. Rather the time dimension appeared to be working against the idea of life being 'easy'. It seemed to be working towards life possibly being unique.
Probably true, but how much of that early span is the question.Consider, that the earth is a little older than 1/3 the age of the universe. In other words, no planet has had more than three times as long to develop life than Earth. Further, it seems unlikely that a small but significant portion of the early lifespan of the Universe could possibly support life.
Here we disagree. It's easy for me to imagine a catastrophic collision of bodies. It's also very easy for me to imagine so-called intelligent beings extinguishing themselves in a war of sorts. For the record, I doubt life evolved on Earth in the past, but I also doubt it hasn't arisen and died off elsewhere in the universe. Earth is 1/3 the age of the universe and life has existed for only a fraction of that time so there is almost an incomprehensible amount of time for life to rise and fall.Consider, that it is almost impossible to extinguish life once it takes root. Life can survive in the most precarious situation. There are calculations about life surviving even the hellstorm of a "planet killing" asteroid. There are suggestions that life can survive the cold heartless vacuum of space. I think you too easily reach the conclusion that life could have started and extinguished on Earth in the past. Extinction is a difficult thing to achieve. Sure, it is possible and I cannot rule it out but there is no evidence that such a thing occurred. To expect it to happen requires you to first accept the hypothesis that life is 'easy'.
Complete agreement here.Given that we had not found life that had developed twice on a planet with an age roughly equal to 1/3 the age of the Universe (with near perfect conditions for life) it is not hard to make the argument that life might be so uniformly unlikely as to have occurred only once.
Now of course all of this assumes that life follows our template. While I would not doubt that other life types could exist, it seems unlikely that they could have formed in an environment without active chemistry. That tends to suggest that you would not see life arising spontaneously in frozen states or plasma states or in areas absent of significant amounts of building blocks of whatever type. The Universe is still large when ruling all of those places out but it shrinks quite a bit when you require some form of liquid (certainly less than the merest fraction of one percent of the volume of the universe).
Now your shock is clarified. Using arsenic is surprising given how deadly it is to all previously known life forms. Of course the reason it's deadly is that is is actually a pretty good phosphorous mimic so it's not surprising that a bacteria evolved to actually use arsenic. I wonder what happens if you withdraw arsenic and add phosphorous.Item 2. I am no longer certain that this represents what I thought at first. If this bacterium uses DNA with the same base pairs and is actually just an evolved life form, it is not that big of a deal to me. In other words, it might well suggest that life can exist in a variety of environments that we did not conceive of. It would not suggest though that it evolved separate from the solitary Tree of Life that we see on Earth today. We already knew from our study of chemoautotrophs that life can exist in places that we would not first have thought possible (think no sunlight as an energy source).