The likelihood of life elsewhere in the universe is perceived as high among scientists, though it may be predominantly microbial rather than complex organisms. For the first 4 billion years of Earth's history, life was largely unicellular, with more advanced macroscopic life developing only in the last half billion years. While sampling life across the universe would likely yield primarily microbial forms, the intricate journey of life's evolution on Earth involved many fortunate occurrences across various scales, leading to the existence of complex organisms.
The odds that any given planet's gonna have complex life, I mean, this is really an opinion because we don't know about life anywhere else in the universe, but most of the scientists that I know and think about this deeply, I think the likelihood of life elsewhere is very high. It may not be the sort of life we're used to. It's not giraffes and redwood trees, but at least things like microbes.
When you think about the history of Earth, if you visited this planet for the first 4 billion years of its existence, you wouldn't necessarily be that impressed with its life. It was largely unicellular for that time period. Only in the last half billion years has life gotten big and macroscopic.
If we were to be able to go around the universe and sample life from various places, probably the odds are that most of the time, it's gonna be microbial. That will be biochemically complex, but not necessarily anatomically or behaviorally complex.
A huge number of things had to go right for our species to exist and for each of us individually to exist, for us to be here. And these are at all sorts of scales, the cosmological scale, the geological scale, and the biological scale.
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