I post this in relation to small humanoid found on Mars. I do some research as I am trying to understand the reasons for small size of Martian humanoid, if we of course assume that humanoid beings living on Mars are of simillar size that visible shape taken by Spirit. Insular dwarfism may be simillar mechanism going on on Mars.
Also lack of oxygen may contribute to small size of Martians. There has been some dispute in scientific world about relations between amount of oxygen in the air and size of the body of creatures. Some of experiments have shown, that oxygen levels in atmosphere can be limiting or stimulating factor for body size and planetary evolution (read here). During other experiment I read about, scientist were growing american crocodile embrios in special incubators with different levels of oxygen. And experiment shown, that to some level more oxygen contributed to bigger size of crocodile's body.
Lower gravitation (almost 3 times lower then Earth's gravitation) on the contrary may reduce need of body for oxygen. According to official data oxygen makes only 0.2% of martian atmosphere. If Skipper's photos showing stable liquid water are correct and if we have really seen water drops on Phoenix lander, then I don't believe that martian atmospheric pressure is correct, even though some scientist say, that it is possible with salted water and known pressure (6-10 milibars) (read more here). I suspect, that martian atmosphere is much densier than we have been told, it may be dozen times thicker, and may even have different composition, what would proove proper conditions for life on the surface. Also water (and life) should appear more likely in liquid state in low elevated terrain as marked violet, blue, green on this topographic map of Mars. And that is why they sent their missions where they sent...