> We built lots of what makes Earth habitable. Try removing your clothes, housing, heating, etc. and see how long you survive.
Even a totally unprepared person can survive for many hours with none of these things in most places on earth. If you happen to be near a source of fresh water in a not-too-cold climate you can survive for days, and if there's a natural food source nearby you can survive indefinitely. That is crucial because it means you have a lot longer to build the things you need in order to improve your odds in more hostile environments, and a lot more margin for error when things don't go quite right.
By way of very stark contrast, a human without a space suit will survive for at most a few seconds on Mars. That doesn't leave nearly as much margin for error.
So yes, engineering our environment is integral to our survival even here on earth. Nonetheless, earth and Mars are in on way comparable as a consequence of this.
Your survival time in Minnesota (where I grew up) in the winter time is not appreciably longer than in a vacuum, and you'd sometimes have to spend quite a long time to suit up in order to safely operate in such conditions. Most of the Earth is, in fact, covered in water (much of it cold), and most people would last maybe seconds longer than vacuum. The parent's point is right, IMHO. Humans may have first evolved in climates without necessity for clothing, housing, or fire, but we definitely need it in much of the world. And even places requiring these things still can thrive.
Even a totally unprepared person can survive for many hours with none of these things in most places on earth. If you happen to be near a source of fresh water in a not-too-cold climate you can survive for days, and if there's a natural food source nearby you can survive indefinitely. That is crucial because it means you have a lot longer to build the things you need in order to improve your odds in more hostile environments, and a lot more margin for error when things don't go quite right.
By way of very stark contrast, a human without a space suit will survive for at most a few seconds on Mars. That doesn't leave nearly as much margin for error.
So yes, engineering our environment is integral to our survival even here on earth. Nonetheless, earth and Mars are in on way comparable as a consequence of this.