Portuguese 
English 
Spanish 
8 min of reading 
0 comments 
Study indicates that humans on Mars would be short, with thicker bones and altered skin, potentially becoming a separate species in a few thousand years.
When Hollywood imagines humans on Mars, it shows tall, slender, and elegant people — figures elongated by the weak gravity of the red planet. Science says otherwise. According to evolutionary biologist Scott Solomon, a professor at Rice University in Houston and author of the book “Future Humans: Inside the Science of Our Continuing Evolution,” published by Yale University Press, natural selection on Mars would favor shorter bodies, with denser bones and a more robust appearance — possibly resembling members of the extinct genus Paranthropus, a proto-human that lived in Africa over 1 million years ago. The reason, as described by NBC News, Nautilus, and Discover Magazine, is brutal: in gravity that is only 38% of Earth’s, bones weaken — and a fragile pelvis can kill mother and child during childbirth.
The problem that no one sees in movies
The gravity of Mars is 0.38 g — just over one-third of Earth’s. For day-to-day life, this means that a person weighing 70 kg would feel as if they weighed 27 kg. It seems comfortable. In movies, it is. In biology, it is a slow-motion catastrophe.
Human bones need gravity to remain strong. It is the mechanical load — the weight of the body pulling against the skeleton — that stimulates bone remodeling, the process by which old bone is reabsorbed and new bone is deposited. Without this load, bones lose density. Endocrinologist Michael Holick estimates that bone density loss in reduced gravity can reach 50% in the first two to three years. Astronauts on the International Space Station lose about 1% to 2% of bone mass per month in microgravity — and despite intensive exercise, they never fully recover what they lost upon returning to Earth.
-
NASA releases Google Maps resource to track the Artemis II Mission in real time and turns the app into a practical tool to visualize the spacecraft’s position and data directly on your phone.
-
Artificial intelligence helps create new antibiotics and could save millions of lives worldwide.
-
Sodium batteries are approaching the cost of lithium by 2027 and reinforce the trend of technological diversification in energy storage and electric vehicles.
-
The messaging app that came pre-installed on every Samsung Galaxy phone is nearing its end, and the company itself is already advising millions of users to switch to Google’s app.
The childbirth that kills
On Mars, bone loss would not be temporary — it would be generational. Children born and raised in 0.38 g would never develop the bone density of an Earth human. Their skeletons would be adapted to local gravity from birth. And here is the problem that Solomon identified: natural childbirth requires a structurally strong pelvis. A pelvis weakened by low gravity could fracture during labor — killing the mother, the baby, or both.
Natural selection would solve this the way it always does: by eliminating. Women with thinner pelvises and lighter bones would have more difficulty with natural childbirth. Women with thicker bones and a more robust structure would survive longer — and pass their genes on. Over generations, selection would favor compact, dense, and robust bodies. The Martian of the future would not be the elegant alien of movies — they would be more like a short, thick-skulled weightlifter.
Paranthropus: the unlikely model
Solomon suggests that the appearance of future Martians could resemble members of the genus Paranthropus — a group of extinct hominids that lived in Africa between 2.7 million and 1.2 million years ago. Paranthropus boisei, the most well-known, had a massive skull with pronounced bony crests, powerful jaws, and extremely dense bones. It was neither tall nor elegant — it was compact and robust.
The comparison is not with the diet or lifestyle of Paranthropus, but with the phenotype: thick bones, reinforced skull, and solid appearance. On Mars, where low gravity would degrade skeletons over generations, individuals who started with heavier skeletons would have an advantage — their bones would retain enough density even after the loss caused by reduced gravity. Natural selection, in just a few hundred generations, would push the entire population in that direction.
The head that can grow
A surprising side effect: if cesarean births become the norm on Mars — as Solomon suggests they might, given pelvic fragility — the size of the human head would no longer be limited by the dimensions of the birth canal. On Earth, the baby’s skull is compressed during birth to pass through the pelvis. This limitation is one of the reasons why the human brain has not grown larger throughout evolution.
Without this restriction, Martian heads could gradually become larger over generations. More cranial space does not necessarily mean more intelligence — but it does mean that the selective pressure that kept the human skull at a specific size for hundreds of thousands of years would cease to exist.
Orange skin or dark skin: the debate
The skin color of Martians is one of the most divergent points among experts. Nathalie Cabrol, director of the Carl Sagan Center at the SETI Institute, argues that less sunlight on Mars would lead to a gradual loss of pigmentation — colonists would become progressively paler, with lighter hair, as happened with human populations that migrated to high latitudes on Earth.
Solomon disagrees. Mars’ atmosphere is thin — less than 1% of Earth’s — and the planet has no protective magnetic field. This means that ultraviolet and cosmic radiation on the surface is much more intense than on Earth. Melanin, the pigment that darkens the skin, protects against UV radiation. Solomon argues that natural selection would favor darker skin, not lighter — or, in a more radical alternative, that the human body could begin to produce pigmentation based on carotenoids instead of melanin. The result: orange skin, like the color of a carrot. Mars would be the red planet with orange inhabitants.
The founder effect: when 100 people define a civilization
Elon Musk proposed sending 100 people on the first ship to Mars. Scott Solomon points out that this number would create a genetic phenomenon called the “founder effect” — the same mechanism that differentiated Darwin’s finches in the Galápagos Islands. When a new population is founded by a very small group, the genetic traits of those founders become disproportionately represented in subsequent generations, even if they offer no adaptive advantage.
If the first 100 colonists happen to have a high proportion of redheads, Mars will be a planet of redheads. If they have a predisposition to diabetes, the colony will have high rates of diabetes. If they have large ears, Mars will be the planet of large ears. The founder effect is random — it is not natural selection, it is a genetic accident amplified by isolation. And on Mars, where the initial population would be tiny and the gene flow with Earth would be minimal, the accident would become the rule.
The radiation that accelerates everything
Mars has no global magnetic field and its atmosphere is 100 times thinner than Earth’s. This means that cosmic and solar radiation reaches the surface practically unfiltered. For the colonists, this implies a high risk of cancer. For evolution, it means something different: an accelerated mutation rate.
Mutations are the raw material of natural selection. The more mutations occur, the more genetic variants arise for selection to filter. On Earth, the mutation rate is relatively low because the atmosphere and magnetic field protect us. On Mars, the rate would be much higher. “Increasing the mutation rate gives natural selection more material to work with,” says Solomon. The result: evolution on Mars would run faster than anywhere on Earth.
6 thousand years to become another species
Solomon estimates that, in just a few hundred generations — perhaps as little as 6 thousand years — a new type of human could emerge on Mars. Not necessarily a species separated by the classical definition (unable to interbreed with Earth humans), but a physically distinct being, with anatomy, physiology, and possibly immunology different from ours.
Astronomer Chris Impey from the University of Arizona ponders that appearing physically distinct would be much faster — perhaps dozens or a hundred generations — but that complete speciation would take hundreds of thousands of years. The theoretical biologist Philipp Mitteröcker from the University of Vienna is more skeptical: human populations on Earth have remained isolated for thousands of years without becoming separate species. Divergence exists among scientists, but they all agree on one point: Martian colonists would not remain the same as us.
The immune system that forgets how to fight
Mars appears to be sterile. If the colony is built as a closed and germ-free environment, the colonists would live without exposure to Earthly bacteria, viruses, and fungi. Over generations, their immune systems would lose the ability to combat infections common on Earth. An Earth cold could be fatal for a Martian.
This immunological vulnerability would create a practical barrier between the two populations. Colonists would avoid close contact with Earth visitors for safety — including sexual contact. This would reduce gene flow between Earth and Mars and accelerate evolutionary divergence. The same logic that separated species on oceanic islands would operate between two planets separated by 55 million kilometers of vacuum.
The irony that Musk did not mention
Elon Musk said in 2016 that humanity has two paths: to become a multiplanetary species or to await extinction on Earth. Stephen Hawking agreed. Colonizing Mars is presented as a lifeline for the species. But Solomon points out the irony embedded in this proposal: the strategy to preserve Homo sapiens may be exactly what transforms it into something that is no longer Homo sapiens.
“This routinely happens with animals and plants isolated on islands — think of Darwin’s finches,” Solomon wrote in Nautilus. “But while speciation on islands may take thousands of years, the accelerated mutation rate on Mars and the extreme contrasts between Martian and Earth conditions would likely speed up the process.” Becoming a multiplanetary species may mean becoming multiple species.
The cyborg path
Astronomer Chris Impey from the University of Arizona suggests that Martian colonists would likely not wait for natural evolution. “They will be aggressive in genetic engineering and self-modification — enhancing and replacing parts and organs of the body — to the point of incorporating monitoring and repair devices, following a cyborg path,” Impey told NBC News. The colony would consist of technologically advanced people who would deliberately alter their own bodies, without waiting for natural selection to do the work.
In this scenario, the divergence between Earthlings and Martians would not only be biological — it would be technological, cultural, and philosophical. Martians would develop their own dialects, social norms, and values. Separated by distance, by biology, and by choice, they would cease to be “us” long before they ceased to be Homo sapiens.
The mirror that Mars shows us
The question of how humans would change on Mars is not just about Mars. It is about what it means to be human. Our body is the product of millions of years of evolution on a planet with 1 g of gravity, a strong magnetic field, a dense atmosphere, and billions of species of microbes. Remove any of these variables and the body changes. Remove all of them at once and the result, in just a few hundred generations, is something we would not recognize as ourselves.
Solomon is not saying that colonizing Mars is wrong. He is saying that it has consequences that no one includes in the slide presentation. The plan to make humanity multiplanetary may work — but the price may be discovering that, on the other side of the journey, those who arrive are no longer who left.
Seja o primeiro a reagir!