Life on Earth evolved in a never ending battle to be the most well adapted species to its environment. Consequently it can be said that the life forms that evolved here on Earth are specialist biological machines with certain requirements that must be met in order for them to thrive. It then comes as no surprise that entire species can be wiped out by small changes to their environment as their specific adaptations no longer provide them the advantage that they require. However there’s one particular pressure that all life has evolved with that, at least for most life, will never change: gravity.
Many biological processes rely on gravity in order to function correctly and for the longest time it was thought that no life that evolved here on Earth could survive a zero/microgravity environment for long. Indeed medical doctors back on the Mercury program were very sure that the second their astronauts went into orbit their vision would blur, rendering them incapable of performing any tasks. The truth of the matter is whilst we’re designed to work well in our standard 1G environment our bodies can cope quite well with microgravity environments for extended periods of time, provided certain precautions are taken.
What’s truly fascinating to watch though is how other creatures function without the aide of a constant gravitic pull. Indeed quite a lot of science done aboard the International Space Station has been centred around studying these effects on varying levels of creatures and some have produced very interesting results. For example spiders sent up to the ISS don’t spin webs like their Earth bound relatives do, they instead weave what looks like a tangled mess all over their environment. It would seem that their sense of direction heavily relies on figuring out which was is down and absent that their webs lose their usual symmetry.
Other animal species seem to adapt rapidly to the loss of gravity’s unrelenting effects. Mummichogs, a type of small fish, appear to be quite hardy little creatures in microgravity environments. They suffer some initial confusion but after a short while they appear to be quite capable of swimming perfectly well in microgravity. Ants too seem to adapt rapidly to the loss of gravity with their nests taking on an almost surreal structure that is not like anything you’ll see on Earth. The habitat that NASA designed to take ants into space is also quite incredible being a clear blue gel that contains everything the ants need to survive both the trip up and life aboard the space station.
Incredibly some species appear to be better suited to microgravity than the regular 1G environment on Earth. C. Elegans, a type of unsegmented worm, not only adapted to life in space but showed a marked increase in life span over their earth bound cousins. The cause appears to be a down-regulation of certain genes associated with muscle ageing which in turn leads to a longer life. Whether the same genes could be down-regulated in humans is definitely an area for investigation but as everyone knows us humans are far more complicated beasts than the simple C. Elegan.
Indeed whilst muscle atrophy is one of the biggest problems facing astronauts who spend a long time in space there are several more concerns that also need to be addressed. Unlike the C. Elegan we humans have an internal skeleton and absent the effects of gravity it tends to deteriorate in much the same way as it does in bed ridden patients and people with osteoporosis. Additionally whilst the ISS is still within the protective magnetic field of Earth it’s still subject to much higher levels of radiation than what we get here on Earth which poses significant health risks over the long term. There’s also a whole swath of things that don’t quite work as intended (burping in microgravity is fraught with danger) which we’re still working on solutions for but suffice to say if we’re ever going to colonize space reproducing the effects of gravity is going to be one of the most critically required technologies.
It’s not often that we get the opportunity to effectively remove a unyielding constant and then study how much it influenced the development of life here on Earth. This is one of the reasons why space based research is so important, it gives us clues and insights into how dependent our biological processes are on certain key variables. Otherwise we’d figure that gravity was simply a requirement for life when now we know that life can survive, and even thrive, in its absence.