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.
