Actually a major event, The Quanternary Extinction, occured something like fifteen thousand years ago almost exclusively in the western hemisphere (gamma ray burster?). It killed all the large critters.
That aside...why mars? why not the moon. Or asteroids? Why not hollow out eleventy seven thousand asteroids, put a spin on them, and colonize the asteroid belt?
well moon doesn't have flowing water like mars, also it's gravity is just too low and it is very small in size to be a 2nd Earth.
The asteroids are too far away and impractical for settlement given their irregular sizes.
Mars does not have flowing water. In fact it does not have any liquid water at all. It's well below freezing everywhere on mars. All of the water on Mars is ICE.....or frost. Mars barely has an atmosphere.
The problem with low gravity is?
Mars is 4,212 mi in diameter...the moon is about half that at 2,159 mi
At just 0.38 of the Earth standard, a person who weighs 100 kg on Earth would weigh only 38 kg on Mars.
Your weight on the Moon is 16.5% what you would experience on Earth. In other words, if you weighed 100 kg on Earth, you would weigh a mere 16.5 kg on the Moon. For you imperial folks, imagine you tipped the scales at 200 pounds. Your weight on the Moon would only be 33 pounds.
I've been trying to lose weight for a long time. I like that.
Some asteroids come closer to the earth than does the moon. It might be in our best interests to do something about that.
it was just very recently discovered that mars has, in some places, liquid flowing water.
http://www.nasa.gov/press-release/nasa-confirms-evidence-that-liquid-water-flows-on-today-s-mars
the problem with low gravity is that there will be significant loss in bone density and muscle atrophy. the rest you can read here:
http://www.philforhumanity.com/Colony_on_the_Moon.html
asteroids are best suited for mining. To be a viable alternative to Earth it needs to at least be half the size of earth because we will quickly want to scale population.
Mars is barely half the size of earth.
http://www.lpi.usra.edu/publications/slidesets/redplanet2/slide_1.html