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I think the hard steps are sharp divisions that had a long time in the status quo, then a sudden random development. Single-cell to multi-cellular. Developmen

I think the hard steps are sharp divisions that had a long time in the status quo, then a sudden random development. Single-cell to multi-cellular. Development of nerve tissue that can collect information, make decisions, and influence the organism. Centralization of a bundle of nerves into a decision making center. Then you get to higher order steps that probably aren't as complicated, such as communications and organization, then all the steps that humans went through that took a while, without having major biological changes that enabled them.

DavidSJ 6y ago
I think any step which occurred independently on multiple occasions is probably not a hard step. The origin of multicellular life from unicellular life occurred on at least three separate occasions independently. However, I think at the very least that the origin of the first cells, as well as perhaps the transition from Archaean/Prokaryotic cells to our symbiotic Eukaryotic ancestor may qualify.