Spore's genius in allowing any permutation of creature to move around is still there. The aforementioned knees proved no problem, even though, after an evolutionary step, they'd result in a creature that's basically foodstuff for larger predators. Not to worry: another trip to the editor and the little purple creature emerges with more appropriate knees.
When you progress to the land, your goal is to procreate and build up your tribe. It's tough up there - you have to be like a Star Trek captain and make first contact. The odd-kneed critter walks up to other species and initiates a conversation which, luckily, doesn't resolve itself with running away. The other creature looks like a Futurama character's worst nightmare, but responds sweetly, echoing the same trilling. A successful contact is made and, more importantly, more DNA points are gained. As you create a village, it's necessary to spread around a little. Soon that single point of contact's trying to woo whole tribes into its extended family. Sometimes it works, sometimes there's a ruckus. A friendly encounter will lead into a bigger village, then city building.
From Will Wright's grandiose idea there's finally a game emerging, one where violence and communication are central to success. It's as much about exploration, conquering and loving as it is creating.