Earth is not all that inhospitable even if you lack technology. There are something like 10 quintillion insects inhabiting earth. The number of bacteria is several orders of magnitude greater. These things all get by just fine thanks to Earth's sweet conditions.
But if you dropped a colony of one of these natural survivors on Mars, it would simply die. Even what we consider to be harsh environments on Earth (e.g. Antarctica, the bottom of the sea, the top of Mt. Everest) are quite hospitable relative to the average on Mars.
But if you dropped a colony of one of these natural survivors on Mars, it would simply die. Even what we consider to be harsh environments on Earth (e.g. Antarctica, the bottom of the sea, the top of Mt. Everest) are quite hospitable relative to the average on Mars.