"Rare Earth" perspective on the subject
One of the most important differences between the Earth and Mars, according to Peter Ward, is plate tectonics. On Earth, plate tectonics does everything from provide a stable global temperature, which is necessary for the evolution of complex life, to recycling chemicals to keep the volume of carbon dioxide in our atmosphere relatively uniform. It also created the continents, which helped to create the large amount of biodiversity and aids in creating the magnetic field that surrounds Earth. All of these are important to the development and maintenance of complex life, and, except for a brief time, in which volcanoes were created, it doesn’t exist on Mars.