What adaptions would humans obtain if they lived on Mars? (eg. get taller/shorter because of gravity)
In a universe where humans terraformed mars to have breathable air and house some plants, what would happen to humans? Physically?
I suspect that visual inspection of a Martian colonist would reveal no differences from standard Earth people. This is because humans are not going to sit around and wait to evolve. If they have the technology and will to Terraform Mars (or anyplace else, for that matter) they will also be augmenting themselves through biotechnology to live and thrive in that environment.
Terraforming eliminates the need to make very drastic external modifications anyway. The temperature and atmosphere are being changed to conform to the averages of Earth (by definition), so there is no need to grow an insulating fur coat, or develop extra sets of lungs, for example.
Only if you were to subject the colonist to detailed microscopic or forensic examination would differences become apparent. The Martian colonist will have their bone structure modified to maintain strength and density despite the lower gravity. Metabolic processes will be more efficient than on an unmodified human in order to maximize resources, especially near the beginning when everything needs to be imported. Balance and reflexes will be rewired to account for the lesser gravity, and perhaps there will be a need to increase the pigment melanin to account for the limited magnetic field and ozone on Mars and the high levels of ultraviolet radiation in the environment.
If Mars is colder than Earth on average, there might be selection towards the Inuit physique, maximizing volume while minimizing surface area. Once again, this would be a conscious choice engineered into the colonists by the first generation rather than natural selection working its wonders and allowing a dormant trait to reassert itself.
How this would be done is going to be through a combination of genetic engineering, microbiome tweaking and possibly some cyborg technology (at least until the genetic engineering part is perfected. Maybe first generation colonists can be identified by the cyborg implants they wear).
So short answer: people will not evolve to fit the environment, they will engineer themselves to live and thrive in the environment without changing their external appearances.
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. 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
Here are some of the possible effects.
1- Lower gravity: thinner bones (starting with the settler themselves)
2- Lower gravity: taller heights (starting after a couple of generations)
3- Lower gravity: lesser muscle mass (starting with the settlers themselves)
4- Thinner atmosphere: larger lungs (starting after a couple of generations)
5- Thinner atmosphere: weaker hearts (starting with the 2nd generation)
6- Lower gravity: weaker immunity (starting with the settlers themselves)
7- Lack of minerals in food: weaker physique, increase in chances of severe illness and death (starting with the 2nd generation)
8- CCl$_4$ in the dust: body wastes away to a slow, agonizing death (starting with the settlers themselves)