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This is my first ever question on here.

I've seen a few posts on Martian physiology but since the answers on here are answered so well and by so many I thought I'd be more specific.

How would human physiology have changed over 3000 years, providing biomes to replicate Earth's atmosphere?

Following that, how would a present day human feel to meet them and know the martians they are conversing with were descendant of themselves. How would you feel to meet your Martian future descendant and what would you want to talk about? What do you think they'd ask you?

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    $\begingroup$ Welcome to Worldbuilding! You may want to take the tour and peruse the help center in order to become better acquainted with the expectation of this site. In particular, this site is not a discussion forum... "How would you feel to meet your Martian future descendant": Probably feel just as Emperor Charlemagne would feel if he met me. Probably Emperor Charlemagne would ask me how is the (Frankish) Roman Empire doing, and would be disappointed to find out that it is no longer of this world. Honestly, I don't think that humans separated by three millennia of history would have much to talk about. $\endgroup$
    – AlexP
    May 20 at 20:58
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    $\begingroup$ This asks a few questions. By their rules you're supposed to ask one (I don't know why). Also, asking "how would you feel" is an opinion poll, also not by their rules, and asking what they would ask is asking about a character, sigh, also against the rules. I hate to mention all that, but asking how they'd change over 3000 years, generating a new race of Man selected for a different gravity level, is already a pretty decent question. $\endgroup$ May 20 at 21:09
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    $\begingroup$ This will attract attention of close voters for the reasons Serfas lays out. From now on when I see a question from a new user that is overambitious I am going to edit it. $\endgroup$
    – Willk
    May 20 at 21:41
  • $\begingroup$ Thank you for the concise and speedy replies. The comment on Charlemagne, although glib was also poignant and confirmed my own feelings on the anthropological age gap. The gravity effects will certainly be most useful reading, too. I am sorry I was a bit over eager to post. I'll read the rules $\endgroup$ May 20 at 22:27
  • $\begingroup$ What will MARS be like after 3000 years of human habitation? $\endgroup$ May 20 at 23:25

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3000 years is practically "earlier this morning" in terms of biology and evolution for humans. 3000 years is about 90 generations. It's not enough time to have significant changes in physiology: we are still the same as the ancient Egyptians or Mesopotamians, and it has been more than 3000 years ago.

As it was commented in this other answer of mine by Jdunlop:

The Inuit probably developed their layer of subcutaneous fat over the time from the last ice age to the present - about eleven millennia.

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    $\begingroup$ +1 evolution requires a survival / reproduction bias for particular attributes. It is arguable that in our current society that evolution has stopped, with even detrimental attributes that would previously have prevented reproduction being overcome by medical technology these day. $\endgroup$ May 21 at 7:19
  • $\begingroup$ The Ancient Egyptians or Mesopotamians were much smaller than modern man due to a different environment. i.e food in the fridge. Well, except for that one really tall guy. $\endgroup$
    – Daron
    May 21 at 10:34
  • $\begingroup$ @Daron: Were ancient Egyptians all that much shorter than modern Egyptians? (Please note that it makes little sense to average average height across disparate geographical populations.) AFAIK, in the loooong course of the history of ancient Egypt the average height fluctuated between just about the same as for modern Egyptians (about 169 cm in the Early Dynastic Period) to about 8 cm (3 inches) shorter (about 162 cm in the New Kingdom). The average pharaoh was about 166 cm tall, about 4 cm (1½ inches) shorter than the average modern Egyptian. Is that "much" smaller? $\endgroup$
    – AlexP
    May 21 at 13:31
  • $\begingroup$ @AlexP First, ancient Egypt is not that useful for that question because ancient Egyptians were genetically a totally different people than modern Egyptians. In fact, it is somewhat unclear who they were and where they went. For Europeans, were the genetic history is more straight forward, people become massively taller since around 1850, like 20 or 30 centimeters on average comparing medivial Dutch men to current day Dutch men. $\endgroup$
    – quarague
    May 21 at 14:37
  • $\begingroup$ @quarague: "Ancient Egyptians were genetically a totally different people than modern Egyptians": Citation needed. This is . . . completely against common historical understanding. (At least, as it was 30 years ago when I was interested in such subjects. Maybe a staggeringly surprising discovery has been made since.) Where have you read this? And yes, in Europe people became much taller in the second half of the 19th century. About as tall as they were in the Late Antiquity and Early Middle Ages. Quiz: When did Europeans became as short as they were at the end of the 18th century? $\endgroup$
    – AlexP
    May 21 at 16:38
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Background trivia

For a true human example of evolution over a few thousand years, evidence the teeth.

The Shape of the Matter Over the course of the last few thousand years, the human jaw has changed shape dramatically. One of the broadest trends has been a steady decline in the size of the jaw. From around 35,000 years ago to about 10,000 years ago human jaws and teeth decreased in size by about one percent every 2,000 years. For the last ten thousand years, that pace has increased to roughly one percent every 1,000 years. In pace with our shrinking teeth and jaw, the structure of human teeth has changed as well, as thickening enamel and adaptations in technology have cut back our reliance on strong, well-ordered teeth.

Cooking has had one of the largest effects on the development of human dentition. In the distant past, when much of our diet was raw fruits and vegetables, we needed strong and straight teeth. These helped us push our way through the tough, large particles that made up our diet. Cooking has reduced our need for this ability dramatically. At its simplest, the primary goal in cooking food is to break down tough fibers in meats and vegetables, rendering our meals proportionally easier to digest. As a result, the evolutionary pressure to keep our teeth well-ordered has dropped away.

Another example of subtle human changes over time is height.

“Over the past century adult height has changed substantially and unevenly in the world’s countries, according to research published in the journal eLife.

Authors found that people from central and southern Europe, as well as East Asia, grew taller in the last 100 years. Meanwhile there was little gain in height for people from sub-Saharan African and South Asian nations. A few countries experienced decreases in their average adult height after years of gain.

Researchers found that Dutch men, at 182.5 centimeters (about 6 feet), and Latvian women, at 170 centimeters (5 feet 7 inches), are the tallest in the world .

Men from Timor-Leste, at 160 centimeters (5 feet 3 inches), and Guatemalan women, at 149 centimeters (4 feet 11 inches), are considered the shortest.

There would most certainly be changes due to the Martian environment. I would suspect that over 3,000 years, the differences would be small but significant.

And I suspect the changes would have to be more about gene expression and epigenetics than genetic mutation. Existing but unused, unexpressed genes in the human genome would be expressed in a different manner, due to environmental pressures.

While the genome is fixed, the epigenome is much more dynamic. Epigenetic modifications would allow individuals to quickly explore an adaptation to a change in the environment, without “engraving” this adaptive change into the genome. The challenges of epigenetics concern not only medicine and public health (see Epigenetics, the Genome and its Environment) but also evolution (see Theory of evolution: misunderstandings and resistance). Indeed, it casts suspicion on the environment that could modulate the activity of some of our genes to modify our traits, or even induce certain diseases potentially transmissible to offspring. Clearly, the Dutch famine of the winter of 1944-1945 shows that permanent changes have occurred in the genetic heritage of the women who were pregnant at this time and then passed on from generation to generation. This would mean that the trauma also affects the germ cells (sperm and eggs), the only biological link between generations.

I would not expect major physiological changes over this period, but I would posit instead a myriad of subtle changes that, because they are dependent on existing genes in the human genome, and in the unknown Martian environment (it depends a lot on how much Humans adapt that environment) the changes are are unpredictable.

The issue is also compounded by 'selective migration'. I would expect that those who migrate to Mars would be a unique sub-set of the human genomic code. The entire colonization of Mars would be beset by complications and hazards, with a unique selective process. Humans that can survive the trip and the colonization experience, survive. Those that don't, either die or return to Earth. The genetic makeup of Martians over 3,000 years would be very dependent on the genetic makeup of the first thousand or so colonizers, who would have been subject to extreme 'self-selection' criteria.

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Tall and Thin

enter image description here

We know astronauts in zero gravity have their bones and muscles reabsorbed. Once they get back to Earth gravity they are frailer than when they started.

For the low gravity of Mars we should expect a less pronounced version. Some bone and some muscle will be reabsorbed or simply not grow in the first place.

Gravity is the main difference since you say the environments are otherwise designed to match Earth. Though it would be interesting if 1000 years in the ideal environment for the lanky humans was slightly different. The new environment could encourage further mutations.

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    $\begingroup$ This presupposes that humans are able to adapt in the first place, and that an aritificial gravity higher than the 1/3g Martian gravity is not a sine qua non condition for humans to last multiple generations, this we don't know. Otherwise +1 for the Giacometti martian $\endgroup$
    – qq jkztd
    May 20 at 22:14
  • $\begingroup$ @qqjkztd Agreed that is a necessary assumption. $\endgroup$
    – Daron
    May 20 at 22:45
  • $\begingroup$ Totally bizarre, -1... in 3000 years the human species won't change its proportions that much. And with the same argument (gravity) you could argue people would become fat. It all depends on the circumstances. When humans reside on Mars for 3000 years, they prosper. Else they would not stay there. $\endgroup$
    – Goodies
    May 21 at 0:34
  • $\begingroup$ @Goodies Do astronauts get fat? $\endgroup$
    – Daron
    May 21 at 1:03
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    $\begingroup$ Yes, and then they are promoted to gastronauts! I'll show myself out... $\endgroup$
    – acpilot
    May 21 at 5:29
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None.

https://en.m.wikipedia.org/wiki/Lamarckism

Is refuted long time ago. Giraffe does not grow taller because it wants leaves higher up. Small giraffes die from starvation.

Specie must let their members die, a lot, a whole piles of body, every second creature must die, or at least be stopped from reproducing, for it to have any significant evolutionary effect in this timeframe.

People dont let each other die, and dont try to make others not reproduce. Well, in a perfect world at least.

Who will die on mars? People who break chain of command, act reclessly, take unneeded risks, practice extreme sports. Those traits may be slightly reduced, but still, even in extreme case, these traits have almost zero effect. These people also reproduce faster, that offsets the negative side of this behaivor.

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  • $\begingroup$ Just for the sake of argument, how has Lamarckism been refuted? $\endgroup$
    – Daron
    May 21 at 12:58
  • $\begingroup$ @Daron direct contradictions - body parts that keep being changed but are restored in next generation. Hymen, hair and nails, tooth, fractures and scars. More recent - mendelian inheritance and math associated with it. Most recent - dna, that we can actually read and see what traits are passed down. Most extreme lamarchists could argue in favor of epigenetics acting the way they want. But it quickly turns into god of the gaps, as we discover more about how epigenetics works, and what it is responsible for. And that is not a lot between generations, definitely less than ordinary genetics. $\endgroup$ May 21 at 13:10
  • $\begingroup$ And epigenetics storing not a lot of information is not an exaggeration. We are talking about just a few characteristics, and only those that affected the individual so hard that his whole body responded. Like hypoxia, or a toxin. Condition so hard that would kill some % of the population. It is very unlikely that mars colony would allow their people to suffer enough for such effects, by denying them air, food or water or poisoning them, their entire lives. And it is not directly associated with conditions that are never met on earth, like lower gravity. There is just no evolutionary mechanism $\endgroup$ May 21 at 13:28
  • $\begingroup$ And even if that is still seems like 'well, why not', consider how much information is available on epigenetics. ncbi.nlm.nih.gov/pmc/articles/PMC4929538 - it is next to none if inheritance is considered. This is why i consider this line of reasoning to be extremely bad. It heavily relies on god of the gaps type of reasoning, with just some 2 out of 50k papers being remotely relevant, with no good mechanism to read this epigenome yet, with an extremely long list of failures of lamarckism - it failed every time it was tested. For more than a 100 years. $\endgroup$ May 21 at 13:32
  • $\begingroup$ And those parts that do seem to work, like oxidative stress, have absolutely nothing to do with mars or long legs. And even if all of that is ignored, and you still want to dive in, at least be consistent. Epigenetics would limit changes to just 1 generation. Epigenetics has no way to 'carry over' information further. Either this particular creature carries marker of oxidative stress, or it does not. There is no log of old states for epigenetics. When it changes, old state is erased. It state is just a condition of dna storage type. You can tangle the dna or you can keep it straight.No history $\endgroup$ May 21 at 13:37
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People would be generally less muscular and have less dense bones due to growing up in lower gravity, but other than that, it's hard to say.

3000 years, which amounts to 30ish generations is plenty of time for genetic adaptation, but conditions other than gravity would likely be a major factor in reproductive fitness. For example if people have to live in cramped spaces, shorter people would have a clear advantage. As in they'd obviously be less likely to get injured, but also are just generally more successful and productive in their everyday lives, hence more popular and more likely to have offsprings.

Also traits that are completely incidental might become wide-spread. For example, suppose that some early red haired colonists had some genes that make them healthier in the Martian environment (e.g. they don't get scurvy as easily or some such thing). That gene would quickly become wide-spread in a few generations, but so would the alleles that cause red hair and Martians would be more likely to be red-haired than Earthlings.

Besides gravity, one thing that's different on Mars is that it doesn't have a strong magnetic field like Earth. Thus Martians would be constantly bombarded with way more radiation. Resilience to cancer due to radiation would be a highly adaptive trait, even if it would be accompanied by some adverse genetic condition.

Basically, you can just make some stuff up and come up with some plausible excuse for why the Martians have evolved to be different.

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