Think about these things though... The Earth was placed at the perfect distance from the sun to sustain life - chance? A few miles more or less and human life would be impossible. That's only one example of the many miracles that seem extremrly unlikely to have occurred by chance alone.
Actually the Earth orbits in an ellipse. The difference aphelion and perihelion, the furthest and closest distances between the earth and sun, respectively, is approximately 5,000,000 km (3,100,000mi). Clearly life can survive within the 3.1 million mile band around the sun where the earth orbits. The entire habitable zone for earth-like life is between .95AU and 1.37AU, or a band of 39 million miles in width. Just passing through for science.