[ExI] Homo radiodurans (was Maximum Jailbreak)

Stuart LaForge avant at sollegro.com
Fri Oct 26 03:40:26 UTC 2018

John Clark wrote:

>>> My question about living in space:  what do you do about the
>>> radiation for the long term?
>> Simple, you genetically engineer your space humans to be black. Not
>> African black and not just the skin, but pitch-black and including the
>> internal organs.
> That would give you some protection against ultraviolet light and maybe
> even a little against soft X rays but no protection at all against the
> most dangerous and hard to shield against type of radiation which isn't
> electromagnetic at all, its high speed particles in the form of Cosmic
> Rays.

Yes. You are right and I am guilty of not properly explaining an idea that
I have been kicking around for some time. That being how to best engineer
and adapt humans to living in space for the long term. I imagined an
offshoot of Homo sapiens called Homo radiodurans that would essentially be
humans that had been genetically engineered to better survive the rigors
of space travel and long term habitation.

I named them for their resistance to radiation but I have imagined other
adaptations as well. For example, they would be small by terrestrial
standards perhaps 4 feet tall or so. Size is not an asset for people who
live in cans. I also envision them being able to enter cryptobiotic
suspension for long journeys and such.

Homo radiodurans would owe its radiation resistance to being engineeered
with specific genes from several known examples of extremophiles that can
withstand several orders of magnitude more radiation than would be lethal
for a human.

You already know about the black melanin producing radiotrophic fungi that
photosynthesize using x-rays and gamma rays and we might be be able to get
away with simply over-expressing our own melanin genes. But you are right
that such would be no defense for cosmic rays of the particulate variety.

Therefore I have turned to other extremophiles such as tardigrades or
"water bears" and the bacterium Deinococcus radiodurans, which inspired
the name of these engineered humans, for solutions. Tardigrades are
notable for having survived being directly exposed to the hard vacuum and
radiation of space for several hours, so they would be the gold standard
for what we could accomplish given the will to engineer our germline.

Particulate radiation like high energy protons damage DNA by causing
double stranded breaks and knocking electrons about generating reactive
free radicals.

Organisms that are highly resistant to radiation generally utilize a
strategy of gene redundancy and extremely efficient DNA repair and free
radical quenching. In other words, they have multiple copies of their
chromosomes and several copies of every gene that encodes for DNA repair
enzymes and antioxidant enzymes.

Humans have DNA repair enzymes as well, but they are not as efficient or
numerous as those of tardigrades. For example, humans have about 10
varieties of superoxide dismutase (SOD) and enzyme that deactivates oxygen
free radicals while tardigrades have 16.

Tardigrades also have some unique DNA repair enzymes as well. One of which
was actually already introduced into human cell lines a couple of years
ago as reported in nature.



The upshot of the experiment is that the transfected gene protected the
human cells from radiation that killed off the control cells. This is
proof of principle that Homo radiodurans is at least theoretically

Other strategies would involve conditioning astronauts with gradually
increasing dosages of radiation prior to sending them into space. There is
some evidence that people can adapt to radiation in this fashion. The
phenomenon is called radiation hormesis.


However all these biological adaptations and strategies need to be used in
conjunction with hardware like adequate shielding of spacecraft and
habitations. At the end of the day, no matter what genes you have, a
proton with the kinetic energy of major league fastball pitch is going to
do some damage to your cells.

Space is the most hostile environment we have ever faced. For that reason
alone we must conquer it if for no other reason than to test ourselves
against eternity.

Stuart LaForge

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