A popular trope of science fiction is a world in which creatures with unusual body plans rule. From the octopoid Martians of War of the Worlds to the giant “bugs” of Starship Troopers, there is a creepy appeal in the idea that a race of spineless creatures could pose a real threat to humanity.
Because as far as we are concerned, the backbone is king. Whether or not we are truly the “dominant” organisms on Earth is debatable. But we are vertebrates – and so are most of the large, charismatic animals that walk, swim and fly. It is only natural that we find ourselves drawn to what Henry Gee, Senior Editor at Nature, calls “our own corner of creation”.
The spine is certainly a useful innovation. It provides support for the body, as well as valuable protection for the spinal cord. The fact that our bodies are supported by an internal skeleton as opposed to an external one also allows for a greater range of movement, and means vertebrates can grow to far greater sizes than any invertebrate ever has.
But seeing as over 90% of all animals get by just fine without backbones, it is not obvious why this novelty arose in the first place. How did the spine emerge from a spineless world?
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