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(ominous music)

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On Mars you would have a feeling

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like we're just not familiar with.

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You feel lighter than you do on Earth.

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Like that sort of strange sensation you have

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when you're walking in an airplane and it starts to descend.

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On Mars life will feel both strangely familiar

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and unlike anything we've ever experienced before.

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Extreme isolation, tens of millions of miles from home.

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As we adjust to living on the Red Planet

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and work to make it more like our Earth,

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inside our bodies something extraordinary

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will begin to take place.

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If humans end up living on other planets, like Mars,

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that could trigger evolutionary changes

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that might lead us down a path

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by which we eventually become new species of humans.

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In the distant future, ready or not,

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we will become Martian.

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(ominous music)

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(moves into contemplative music)

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Humans are built for our planet.

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Our bodies are really configured

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to allow us to walk around on two legs

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with exactly the amount of gravity

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that we experience here on the surface of the Earth.

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{\an8}Our hearts are adapted to be able to provide blood

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{\an8}to all of the parts of our body

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under earth gravity conditions.

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Our eyes are really well adapted to see

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in the light conditions here on Earth.

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Our brains evolved to help us

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to make sense of the environment

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that our species evolved in.

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These changes to our bodies

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took place over grand scales of time.

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So gradually that our ancestors never perceived

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how they were adapting to their changing world.

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(rocket thrusters roaring)

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And now humans are approaching the moment

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when they will leave Earth for Mars.

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A planet with conditions that neither we,

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nor our ancestors, ever faced before.

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We're always under evolutionary pressure.

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But nothing like what people living on Mars will experience.

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The challenge is to adapt to conditions on Mars

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will be more extreme than almost anything that's happened

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in the history of evolution here on Earth.

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Thanks to the International Space Station though,

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we can start to get a glimpse

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of the kinds of changes our bodies will go through

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once we leave Earth.

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{\an8}The most significant hazard present

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{\an8}on the International Space Station is a lack of gravity.

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Aboard the ISS in low Earth orbit

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some of the effects of microgravity become apparent quickly.

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When you go into microgravity,

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a significant amount of your blood volume

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shifts to your upper body.

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And you see the crew members,

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the pictures demonstrate it quite well,

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their faces get very puffy.

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The fluid inside your head shifts as well.

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And you're disrupted by the idea of my ears are clogged,

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my nose is stuffy, my eyes are watering.

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It may not actually be a negative impact

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on how your brain functions,

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but part of your thought process

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is distracted by the distress you feel.

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You're just uncomfortable.

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That persistent discomfort

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might play a role in a phenomenon

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astronauts often complain about, known as space fog.

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The crew members feel fuzzy,

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their functions start to slow down,

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and it takes them longer and longer to do,

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you know, pretty regular procedures

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that we all take for granted.

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Inside the astronauts bodies,

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the lower gravity is driving more substantial changes

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to the muscular and skeletal systems.

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The body is trying to understand the lack of signal.

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The body is stopping its investment

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in things like bone and muscle.

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Bones become more weak and brittle.

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And one particular muscle

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experiences and especially dramatic change.

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In a lower gravity environment

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we expect the heart to become weaker

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because it won't have to pump quite as hard

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to be able to move blood all around the body.

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After a routine mission to space

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lasting a few months to a year,

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astronauts can typically rebuild their muscle and bone mass

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after they return to Earth,

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but we don't know how our bodies would react

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if that mission to space ended instead

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on the surface of Mars,

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where the gravity is just 3/8ths as strong as the Earth's.

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Would we ever regain the strength we had on our home planet?

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If you've watched any of the rovers land,

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it's a rough landing.

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So we have to think about protecting the crew

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because they're no longer as robust as they were

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when they left Earth.

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The potential danger of a broken bone

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would threaten humans as long as they stayed on Mars.

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Imagine breaking a bone on Mars

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and losing the ability to manipulate objects with your hands

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or to move your wrist.

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If you have a broken bone on Mars,

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it's gonna make it really hard

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to do all of the intense physical labor

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that's gonna be necessary to make a living

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and to thrive in the Martian environment.

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You know, the austerity of the environment

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takes, you know, an issue that here on Earth we could fix

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to something that is catastrophic and or fatal.

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How our bodies respond to Mars' gravity

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will not only affect those first settlers.

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It may also affect the evolution of our species.

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If we're able to reproduce on the planet.

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Those who will pass their genes onto the next generation

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will more likely be those who experience

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less cognitive decline and who tend to grow denser bones,

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even in low gravity, than their peers.

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And while the ability to perform manual labor

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on this hard scrabble landscape

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is one area where having denser bones could be a benefit,

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denser bones would be even more essential

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to women during pregnancy.

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During pregnancy a woman's bones already become brittle

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because some of the calcium from her skeleton

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is being transferred to the growing fetus's skeleton.

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At the same time,

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increasing amounts of pressure are placed on the pelvis,

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One of our most remarkable adaptations.

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The pelvis allowed us to walk upright as humans

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and it's the bone which helps females

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support their wombs during pregnancy

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and later deliver their babies.

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If women experience a fractured pelvis during childbirth,

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that could threaten her life and the life of the baby.

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And that means that women that have relatively denser bones

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would be less likely to fracture a pelvis during childbirth,

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and that would make them more likely to survive

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and to be able to pass on their genes for stronger bones.

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Another possibility is if childbirth is just too risky,

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we might see a rise in ceasarean section births.

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Interestingly, if we have a situation

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where most births are through a C-section

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that actually could free up the head

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to become larger and larger

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because the head would no longer be constrained

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by having to fit through the birth canal.

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The idea that when there's a lot of C-section births,

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the head could become larger,

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is supported by studies here on Earth that have found that

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in places where C-sections are especially common,

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like in the US and Brazil,

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the heads of babies are already becoming noticeably larger.

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Over time, humans on Mars

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could develop thicker frames

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or larger heads than their earthbound relatives.

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But to succeed on Mars, our species will need to adapt

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to more the just Mars' low gravity.

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We'll need to develop some protections

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against the persistent radiation that engulfs the planet.

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Radiation, which has the power to mutate our genes

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and perhaps accelerate our rate of evolutionary change.

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So out in space, there are all these energized particles

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{\an8}moving very, very quickly through the solar system,

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{\an8}close to the speed of light.

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Some of them come from our sun and some of them are coming

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from far outside our solar system.

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Mars lacks a magnetic field and without a magnetic field

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{\an8}particles can actually go down

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{\an8}and impact the surface of Mars.

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Like UV radiation,

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the kind of radiation that we're familiar with on Earth,

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those can also cause damage to the molecules in your body.

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For the first wave of settlers,

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this could lead to increased rates of cancer.

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Subsequent generations would be impacted further.

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When you think about reproducing

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on something like the Mars surface,

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DNA damage can definitely be passed along.

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The generational scale of the effects of radiation

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are something we'd really want to understand better

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before we decide we're going to start having families

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on the surface of Mars.

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And these just aren't experiments we can do on humans.

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And on some level, the first people to go live on Mars

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will be our experiments.

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This is part of the uncertainty

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inherent in our future evolution.

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In all living organisms,

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mutations ive species an opportunity to experiment

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with different survival strategies.

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Some of these mutations will lead to failure.

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Some however could lead

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to surprising successful adaptations.

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We know that the pigments in our skin here on Earth

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help protect us from the intense ultraviolet radiation

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from the sun.

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People that live in different parts of the Earth

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have adapted to the different

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ultraviolet radiation environments

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by evolving different amounts of the skin pigment eumelanin.

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Eumelanin is a natural sunscreen

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that protects our skin from damaging ultraviolet light.

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It's possible that people living on Mars

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will adapt skin pigmentation that increases their ability

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to tolerate the intense radiation

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that we experienced on the surface of Mars.

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[Narrator] And the skin pigmentation

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that evolves out of life on Mars

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could look like what we find here on earth,

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or it could be an entirely new pigment for our species.

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Here on Earth some organisms use carotinoids

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to protect themselves from radiation.

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Carotinoids are what give carrots their orange color

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and beta carotene is an example of a carotinoid

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that can be found in sunscreen

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because it helps protect from ultraviolet light.

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It's possible that mutations could arise

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that lead to carotinoids like beta carotene

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being produced in the skin of people on Mars.

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That could make people on Mars develop orange skin.

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Shrunken hearts, heavy skeletons,

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large heads, and orange skin.

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Whatever gives us an advantage

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for surviving Mars' grueling surface conditions

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will become more common in each new generation.

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But evolution is often a grindingly slow process

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and there is no guarantee that a Martian colony

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would survive long enough

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to see these beneficial adaptations

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become common in future generations.

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So what could we do now

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to ensure the success of a permanent Martian settlement?

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It might come down to whom we select

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to be the first settlers.

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I think the first people that will go to Mars

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are gonna have to, first of all, be really hardy.

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We'd want a diversity of skills, a diversity of outlooks,

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a diversity of talents to make sure that

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all of these components that make human culture

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are being accommodated by that group.

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For the Mars missions,

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when you think about the diversity of skills,

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it runs across many disciplines.

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Geologists, agricultural specialist,

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biologists, physicists, astronomers,

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because all of those skills will be necessary

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not only to do the science,

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but to understand how to use and exist in the environment

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that's present.

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And even more important than skill diversity

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will be genetic diversity.

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The one thing that keeps on resonating

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across all of biology is that the more diverse, the better.

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Why, because it gives you a pool of opportunity

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to be responsive and adaptive.

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When you talk about the genetic basis for success,

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you know, for any one gene that represents a vulnerability,

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it also represents a resource.

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The collection of genetic traits

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that make it to Mars

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will determine how future settlers will look, behave,

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and adapt to the planet.

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In the field of evolutionary biology,

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this is known as the founder effect

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and the more genetic breadth the founders carry with them,

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the better chance we'll have of developing the right formula

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for successful human life on Mars.

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To illustrate how the founder effect works,

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we can use colored gumballs

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to reflect some of the genetic diversity

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of the first Martians.

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Each color representing a unique version of a specific gene,

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known as an allele.

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So if we take only a small number of individuals,

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it's possible that we will leave out

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some of the genetic diversity that's present here on Earth.

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And that could be dangerous because some of those traits

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in the genes present here on Earth

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might be valuable in the Martian environment

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in ways that are hard for us to anticipate.

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What if the red gumball was an allele

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that gave people the ability to fight cancer

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caused by the high radiation environment on Mars.

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We might not know that in advance,

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but by leaving out some of the diversity present on Earth,

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we lose the ability to benefit from those genes

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when we get to Mars.

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Humans hold some 20,000 genes.

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And when you consider the number of variants,

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or alleles those genes can exhibit,

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it becomes clear just how much genetic diversity

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our planet's population holds.

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By sending the most diverse founding population possible

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we better our chances of bringing with us

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the advantageous cancer fighting allele,

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represented by the red gumball.

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So if this red trait ends up being really beneficial

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in the Martian environment,

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then in the next generation it might become more common.

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Eventually over several generations

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it might become very common.

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And as generations pass,

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it might eventually be present in all individuals.

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This is the way that natural selection works.

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It makes traits that are beneficial,

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more common from one generation to the next.

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If that cancer-fighting red trait

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were present among the original founders,

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humans could adapt more quickly and more effectively.

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There could also be mutations that arise

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that cause completely new versions of a trait

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that aren't present at all on earth.

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And maybe this now represents

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an even more potent anti-cancer gene

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that makes it even more likely that people can survive

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in the intense radiation environment on Mars.

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And so that trait was spread even quicker

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and replace preexisting traits in the population

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in just a few generations.

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A Martian population,

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all sharing this anticancer trait,

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a trait unique to the planet Mars,

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would be making a profound evolutionary leap.

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The longer that people on Mars remain isolated

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from people on the Earth,

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the more new traits they'll acquire.

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Eventually over time, people acquiring new traits on Mars

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will look more and more different from people on Earth.

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And eventually will give rise

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to a new human species on Mars.

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Eventually we will become Martian.

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The challenges of settling on Mars are infinite.

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But there will always be a degree of uncertainty present

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that we probably will never eliminate

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and that's what exploration is about.

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I think that's what drives us to continue to move forward.

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As a scientist, I'm hopeful that we can survive on Mars.

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I think it's possible that we'll be able to get through

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all of the challenges that Mars will give us

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and be able to actually live and survive.

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This will be one of the most incredible achievements,

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not only in our history, but in the history of all life.

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(tense music)