I had a dream that there was a girl I often saw sitting on a park bench at lunch time. I knew that she often saw me, and one day I decided to sit next to her and talk to her. She was a grad student, it turned out.
I wanted to impress her. It so happened that I had a piece of impressive information: Early on in Earth’s history, a comet came and hit the Earth. It was this comet that seeded the Earth with life. Furthermore, what hit the Earth was only a piece of the comet which broke off. The rest of the comet slingshotted around the Earth and went on to hit Mars. It was this comet which destroyed the nascent life on Mars, making Mars evermore inhospitible to life.
What makes this knowledge all the more impressive is how I came about it: I was on that comet. I had been alive billions of years. I had spend most of the time since that crash living on Mars, unaware that life had evolved on Earth and I needn’t have been so lonely. It was only recently that I had discovered life on Earth and endeavored to go live among it.
So, I thought that this information might impress the girl, but I was concerned that it might instead make her think that I was crazy. Eventually, I decided that it might be better to save this for a later meeting.
Afterword: This has nothing to do with the Cambrian explosion.