Lessons from the timeline

In a rough sense, we can estimate how difficult a step in our evolution is by how long it took to arise.
- Yahtzee example. You might get a 6 on the first roll, but you’ll probably need to roll a lot of times to get Yahtzee (5 of a kind).
- From formation of oceans to life took between 0 and 0.7 Gyr
- From the origin of life to complex multicellular life took 3 to 3.7 Gyr
- From complex multicellular life to intelligent life took 0.5 Gyr
From our sample of one it appears that life is easy to get started, but that complex life is a very difficult stage to reach. Once you get complex life, intelligent life seems to be a fairly easy step.

In a rough sense, we can estimate how difficult a step in our evolution is by how long it took to arise.