What is a human? We come in all shapes and sizes, colours and genders. And yet we find it
still fairly simple to identify in our heads, “Yes, that’s a human,” or, “No, that’s not.”
But this might not always be quite so easy to do. While humans have remained fairly consistent over
the last 10,000 years, there are advances in the works that might make things a little murkier.
We are on the cusp of a technical revolution that might redefine what makes us us.
That technology is gene editing. And it is not science fiction. NASA is already looking into
using it on astronauts, and for good reason. It is likely an unavoidable necessity if we want to
settle on other planets. Why is that? And what are the long-term implications if we let this genie
out of its bottle? And perhaps most importantly, what will it mean to be human 1000 years from now?
I’m Alex McColgan, and you’re watching Astrum. And in today’s video, we will attempt to find out.
There is a pernicious obstacle out there for any would-be space farer. It is one you’ve
likely heard of. But perhaps you’ve not realised how serious it was. Beyond the protective shroud
of our planet’s magnetosphere, radiation is a big deal. Even on Earth, we cannot avoid
radiation. We are subjected to small doses of it every year, just from the rocks that make up the
planet and the tiny amount of cosmic radiation that seeps into our atmosphere. There is no
truly “safe” amount of it, but the tiny dose of roughly 3 millisieverts (mSv) a year is usually
no bother to us. A single mSv is the equivalent of about 3 chest-x-rays, so as these are spread
out over the year it gives our body time to recover from any damage such radiation causes.
But once you start leaving the Earth’s magnetosphere, the radiation dosage goes up.
Merely standing on the Moon increases your dosage 200 times. Solar particles ejected from the Sun
and background cosmic radiation slice through any unprotected astronaut’s body up there,
causing damage to their DNA that can lead to short term acute symptoms like fever,
nausea and vomiting, and also long-term health problems like cancer and sterility.
This is problematic enough that most space agencies put a life-long cap on how much
radiation an astronaut can receive before they’re permanently grounded: around 1000
mSv. Once you’ve been exposed to that much radiation, you’re not allowed into space again.
But problematically, even with all the shielding that humans can muster, it is currently estimated
that the round trip to and from Mars will give you a dosage as high as 1200 mSv.
In other words, a completely fresh astronaut will be able to take one trip to Mars, and their career
will be permanently over. And that’s just Mars. If ever humans want to colonise other places in
the Solar system, such as the icy moon Europa, they would face 5,500 mSv in just a single day.
At that level, their odds of dying in the next 30 days is 50%.
Yet it will be necessary to leave Earth. While it may seem a long way away, 6 billion years from now
our Sun will become a red giant. At that point, it will expand and engulf the inner planets of
the Solar System. Every species on the planet at that time, every work that we humans have created,
will be gone forever: consumed in a raging inferno, unless we’ve spread out to where
our Sun-gone-berserk can’t reach us. And that’s not even to mention the fact that
a planet-ending asteroid could hit us with a dinosaur-level extinction event long before that.
We’re actually overdue the next one, statistically speaking. So going to space seems advisable.
If we have colonies on more than one planet, it reduces the risk of an asteroid taking
us all out – the cosmic equivalent of not putting all our eggs in one basket.
This is why on the 13th August 2021, NASA announced that it had completed a successful test
of genome editing aboard the International Space Station. It should be noted, there are different
levels of gene editing. The test done by NASA was to break the DNA of yeast, remove a section,
and then replace it with a sequence of healthy yeast DNA through a technique known as CRISPR.
As radiation causes damage to DNA, being able to remove segments and replace them with healthy
segments is a convenient genetic maintenance, the equivalent of replacing a puncture on a tyre.
This already would be useful to astronauts travelling through space, as it would allow
them to repair ongoing damage to their DNA by constantly replacing damaged parts of it.
But genetic editing and CRISPR can go one step further.
There is nothing to say that the replacement DNA has to be the same as the original.
CRISPR has been used successfully to implant totally new genes into test subjects,
giving them desirable traits according to the gene-editor’s aims. For instance,
genetic diseases like sickle cell anaemia result in low levels of haemoglobin in the blood.
CRISPR allows these harmful genes to be removed from a cell, and replaced with a healthier version
that does produce the needed haemoglobin. Trials are already underway, to encouraging success.
But it doesn’t stop there. CRISPR can borrow genes from entirely different species.
Tardigrades are microscopic little animals that carry the nickname “Water bears”. Their claim to
fame is that they are resilient to all sorts of harsh environments. They can survive radiation,
desiccation (being completely dehydrated), and have even survived the harshness of space.
That radiation resistance is particularly interesting to us, and the result of a protein
they produce called Dsup. In 2015, geneticists successfully edited the gene that produced Dsup
from tardigrade cells into a culture of human cells. Incredibly, the human cells became 40%
more resistant to radiation. This technology is here, and is already quite accurate and versatile.
Of course, there is still a lot to learn about the human genome. It turns out that the “One-gene, one
trait” model is too simplistic. One gene can do several different things, and editing one can have
unexpected knock-on effects throughout the body. As such, any introduction of tardigrade cells into
humans must be done slowly and cautiously. But it does seem likely that over time, scientists
will understand what each gene does, and how to balance the pros and cons of gene editing. Which
raises an ethical dilemma. Just because we learn how to – and it’s entirely possible that we as a
species will master how to do this – should we? That’s not really for me to answer. But I will
point out that this is already going on. Aside from the ability genetic modification is giving
us to cure genetic diseases, or to repair damaged DNA – which I imagine most people would be fairly
ok with – even genetically modified “designer babies” have already been carried to full term.
Chinese doctor He Jiankui in 2018 announced to the world the birth of two gene edited babies,
Lulu and Nana. The two children had been engineered before birth to be resistant to a
strain of HIV. The only problem was He Jiankui had not told anyone that was what he had been doing.
His work was shut down within days by the Chinese government, and in 2019 he was jailed. But to some
respect, the genie is out of the bottle. And we have to start asking how we would like to see
this technology applied. It may become necessary for anyone travelling to Mars or the other planets
in the Solar System to receive gene therapy conferring on them this resistance to radiation.
And as the techniques for conferring genes from other species improve,
specialised hybrid humans might become more and more common – or even required – in other areas.
While replacing the genes of every cell in our bodies is still a ways away, there is a
possibility that it will one day actually happen. And if it does happen, what would that mean for
us? Well, want to settle on a warm or cold planet, like Mercury or Pluto? Certain traits
might be conferred from extremophiles that give you resistance to extreme temperatures.
There are many species of bacteria out there that survive perfectly well in icy conditions.
It might be useful for any human settling out there to do the same.
Speaking of Pluto, low-light environments might make it advantageous to either gain
improved low-light vision, larger eyes, or to gain traits like echolocation, like dolphins or bats.
1000 years into the future, this will very likely be possible.
How about breathing underwater? We could take the DNA of aquatic creatures, and give humans gills.
That might help overcrowding on Earth too, by allowing us to inhabit oceans,
as well as allowing us to settle on any aquatic worlds we might one day find
Want to travel on long voyages through space? Even with faster rockets, travelling to other stars
might take hundreds of years. It might be useful to be able to hibernate in such a condition,
or to have more efficient energy intake systems, meaning you need less food.
One day humans might introduce chloroplasts into their skin, supplementing energy intake
with photosynthesis, like plants do. Electricians might gain the ability to sense electric fields,
like hammerhead sharks. Our senses might expand into other spectra of light, allowing us to see
x-rays or infra-red. Seeing heat might be incredibly useful in some lines of work.
Seeing radiation might be handy if you’re considering stepping outside into a solar storm.
Our ability to eat a varied diet might increase. There are worms today that can eat plastic.
Maybe we one day will be able to do the same. Increased longevity. Enhanced intelligence. The
possibilities are endless – as extensive as the genetic catalogue of any species that has ever
existed and ever will exist, and even further. One day, we may get so proficient with genetic editing
that scientists will write their own genes from scratch, granting traits as desired. Christopher
Mason, a geneticist and computational biologist who has worked with NASA on 7 projects, believes
in his book “The Next 500 Years” that humans might one day customise their traits on the fly.
“Given the… methods described above, people could find themselves in a state where they decide,
‘I want to turn on these genes for tonight,’ or ‘I want these genes active for Summer.’ “
This is not necessarily a bad thing. Humans already adapt in many different ways.
But it does raise serious philosophical questions about what it means to be human.
Our DNA would no longer define who we are, as it would be under our control.
While initially the technology would likely only be available to the rich, 1000 years from now it
could be so common and so well understood that it could be available to everyone. Even children
could be given homework assignments on changing genes at school, according to some theorists.
What is a human? Is it our DNA? Our ability to communicate? Is it what we look like?
1000 years from now, humans might look more different from each other than ever.
Will it bring a deeper segregation to our society than what we already have? What would the ethical
and moral dilemmas be? Genetic manipulation might even become a question of fashion and
cosmetics – people giving themselves tails or wings for nothing more than the fun of it. It
could be completely down to what they choose. And once humans start spreading out across the stars,
adaptations would cause them to become more and more diverse culturally and even genetically.
Our human race may split off into separate species altogether.
So, what do you think? Would this be a future you recoil from,
or is it one that excites you? I’d love to see your discussions in the comments.