[simiones]

I think the opposite conclusion is true: we know nothing about how life gets started, we know life exists on Earth, we have seen no evidence of life anywhere else, so the reasonable assumption is that life started on Earth.

One thing we know (almost) for sure is that no new forms of life have emerged on Earth for hundreds of millions of years. So we should expect that the conditions required are quite special indeed, or the event is extraordinarily unlikely. As such, it is silly to assume that any other planet is "similar to Earth" in the ways that matter for life appearing based on simplistic observations (temperature, distance from the sun, existence of the most basic required elements).

[LargoLasskhyfv]

Do plants count? Then I have cacti for you, which are thought to be only a few dozen million years old.

[simiones]

I am referring to abiogenesis - life arising from non-life matter. Cacti have not appeared out of simple chemicals, they have evolved from other plant-based lifeforms (in fact, there is no "first cactus").

My point is that, despite the huge abundance of life on Earth today, it is all based on a very old abiogenesis event, with all indications that it was more or less a singular event.

All life on earth seems to be part of the same philogenetic tree, so it seems that life appeared once and then kept evolving from that initial life-form. Of course, there is a good chance that there was some variety of initial organisms that either merged together in symbiotic relationships, such as mitochondria with the rest of the cell, or got out-competed by the one type of organism that we are all descended from. This still indicates that life arose in a single place and only over a relatively short amount of time.

[LargoLasskhyfv]

Hm. OK. thx.