What would alien life look like?

[Anomalocaris]

OK, who thinks that an earth like planet somewhere can and will evolve life very similar to our own here.

I'm more interested in the reasoning as to why it shouldn't.

After all, our mother nature has rolled the die countless times as well and this is our end result?

Can we factor in a similar planet but with a slightly different amount of eg: lithium or silicone, etc. Could that steer evolution in a different direction?

A major question mark is intelligent life. Our planet is about 4.5 billion years old but only in the last few million years or so did evolution favor big brains. The dinosaurs did fine for a 100 million years+ without it until that damn asteroid hit about 65 million years ago.

Current understanding is that extra-terrestrial life is probably very common but intelligent life may be rare.

We just don't know yet.

On the other hand, lineages of non-intelligent extra-terresterial life would likely rarely cross interplanetary divide and perhaps hardly ever cross interstellar divide even when looking at sample pools spanning multiple galaxies. But intelligent alien life may develop interstellar travel capability with significant frequency and thus spread across interplanetary and interstellar divide quite often.

So I suspect that while nonintelligence alien lineages may be very numerous and be everywhere, Intelligent alien lineages, although may be very few, but still can also everywhere.