Terry
Sorry old chap, you've fallen straight into anthropic thinking. Or putting the cart before the horse.
The Sci-Fi writer Douglas Adams likened this to a puddle, marvelling at how perfectly it fitted the hole it filled.
There is only one Earth with exactly what Earth has or had at a particular time in a particular way. That makes Earth a UNIQUE (unlike others) incubator. The fact that there are billions of similar (not identical) planets is not enough.
'Like' doesn't mean 'exactly the same'. A planet with similar composition, albedo, gravity and solar irradiance would probably be 'like' the Earth, just like I am 'like' my brother
If the Earth were closer or farther from our Sun there could be no life. Our placement is unique.
With respect, this is probably utter rubbish.
The Earth's climate (and conditions) could vary quite a bit before life-as-we-know-it was not possible; indeed life probably started when it WAS quite different from now. And there are strong reasons to believe life-as-we-speculate-it could form in vastly different conditions subject to its ability to pass on 'genetic' information with modification.
I don't see how anyone can claim that life evolved elsewhere without evidence.You see, they can't
Yes they can. One can claim anything one likes. Whether it is a reasonable claim, one that is supported by evidence, is a different thing.
Your claim that life on Earth is unique and that there will be nothing like it elsewhere is not supported either way by the evidence (absence for evidence not being evidence for absence is a lot more palatable claim when we are talking about stuff billions of miles away we could not reasonably have evidence of yet), but is not supported by a better grasp of cosmology and biology, and an awareness of the danger of anthropic thinking.
While there is no evidence for life elsewhere, this is to be expected at this time, and cosmology and biology give reasonable certainty to claims life has probably developed elsewhere.
An organism living in the icy upper atmosphere of a gas giant, with ammonia taking the place of water in its biology, would gaze at hard rocky planets close to its sun and dismiss them as possible sites for life due to their searing heat and total absence of liquid ammonia!
To put it simply, just because we are here and can wonder at our existence and note how our environment is perfect for us does not mean other organisms with markedly different chemistry's and requirements for life do not wonder at their existence and note how their environment is perfect for them. Natural selection means we are 'perfectly' adapted for our environments, so of course it seems like they are perfect for us.
And don't make the mistake of thinking ven really smart physicists are good sources of answers for largely biological questions. Well, apart from Feynmann, but he's dead.
Paralipomenon
Overlooked? Mmmm.... or not noticed, like we don't notice ants even though we know they are there?