Actually, scientists found a meteorite in the Arctic that they identified as coming from Mars due to it's composition.
They also found fossils of bacteria in the meteorite. Maybe life came from Mars.
Let me splain something to you.
The universe is only about 15 billion years old. Life first appeared on earth about 3.5 billion years ago. The earth is only about 4 billion years old. It only took about 500 million years for the cell to appear on earth, perhaps sooner. That means that if life came from somewhere else of similar origin it would have taken about the same amount of time to form, which puts that life form back to about 8 billion years ago. That only leaves about 7 billion years left so it would have had to be the starting life form.
Is this what you are saying?
No, I'm just saying that there is a possibility that life here on earth might have been seeded here from somewhere else.
And, development of life forms depends on one main thing, radioactivity which causes mutations, and if the mutations are stronger than what they came from, they mutation takes over.
BTW..............here's a link about the Martian metorites.............
Martian meteorite - Wikipedia, the free encyclopedia