This is hard to answer since the mars changed over time. Even though we know the mars as a red desert without water or life, it is possible, that at some point there was water on mars. Research even shows riverbeds of rivers that once were present on the surface of mars. This could be related to the atmosphere of mars, which may have vanished due to hawking radiation or solar power. Great video about this topic is on the "TED" youtube channel. Here`s a link.
If we would have developed on the mars we know, i guess we wouldn't have differnet lungs, since the air on mars is very differnet from earths, we would probably only consist of 5% water, this is a technique of some microbes to sustain extreme tempertatures ranging from -1K to 420K degrees.
They can withstand temperature ranges from 1 K (−458 °F; −272 °C) (close to absolute zero) to about 420 K (300 °F; 150 °C)
Here's a link
EDIT 1: Since gravity on mars is about a third of earths (0.376 g), we would have less muscles, but in return could be taller since the blood needs less energy to travel greater vertical distances. This also goes for trees and animals, i suspect trees could grow much higher since gravity wouldnt effect them in the way it does on earth, though this is only true if the trees, animals, and humans can adapt to the other envoiremental circumstances like extreme cold, etc. 279
Interesting though is the fact that mars, despite beeing a dessert, is rather cold than hot "min: −143 °C avrg:−63 °C max:35 °C". The seasons on mars are pretty similar to earths, just about twice as long. The Seasonsonal as well as the day-night differences would be tremendous though, because without an atmosphere and without water, warmth is not really "stored" so every night or winter will be way coulder then a day or a summer and transitions would be rather quick, somthing like -6 o'clock :25°C - 7 o'clock: -10°C-. Yet another pretty big difference between earth and mars is the atmospheric pressure which is about 100 times lower than earths, i dont quite know how this would affect us though... Also birds would not be able to coordinate theyre flight and we wouldnt use compasses since mars has no magnetic field. A big roblem would be the periodic sandstorms, which we could maybe compensate with some form of non-visual orientation, or our eyes would be adaptet to sandstorms in another way. Civilisation could be focused around the polar caps, since they contain ice (thus water) maybe, travelling from north to southpole would be considered a difficult journey?
Great topic btw, if you are writing a story or sth along these lines, let me know ;) Hope this helps^^; ~Jan 513