Are astronauts evolving?
Offline I was watching the program Bones last night that dealt with the murder of an astronaut. They discovered he must be an astronaut because of the amount of bone loss. That got me thinking so I searched the web and found this to be a true side effect of space travel. Its so severe and quick that the average space station crew member loses 11% of their bone mass during 1 mission. Considering that the only cause of their bone mass loss is lack of gravity, could this be a sign that their bodies are trying to adjust to this lack of gravity, and such, evolving them. Bones are not really neccessary for a life form that doesn't have to deal with as much gravity, or any at all. A quick look at ocean life shows that. Many oceanic creatures have little or no bones. It makes me wonder, if people lived in a non gravity state for generations, how differently might they look?
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I think since we can't actually breathe in space and live there we won't be evolving a state of little or no bone. But this is interesting none-the-less.
They have to do a lot of excersize up there so they can even walk when they come back down.
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But I think if a life form does much space travel it would design their space craft to simulate their native enviroment as close as possible.
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people in skylab missions have to exercise regularly to keep bone and muscle healthy
People who think there is something they refer to as god don't ask enough questions.
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This is just too weird. I watched a recorded episode of "Bones"* that dealt with exactly this issue. A body was found to have such bone loss that they knew they were identifying an astronaut.
*a series about a anthropologist that works at the "Jeffersonian" Institute based on a real life person
By the way Arletta, gorgeous picture in your avatar!
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Sounds made up...
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Yeah, thats were I saw it, I even mention the show in the orignal post. I love that show!
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That is assinine. Yes whales breathe air. Yes they live in water. They come up for air. Tell me, Einstien, how are we to settle in outerspace and "come up for air" so that eventually we evolve to bonelessness.
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I can't weigh in on the evolution issue because I just don't know enough about the mechanics. However, I was listening to a podcast discussing the new planet with possible earth-like qualities and they stated that the gravity on that planet is something like one and a half times that on earth and then talked about the consequenses this would have on our bodies. For instance, life spans would be shorter, physical stature would be somewhat short and stocky, significant wear and tear on joints, etc. All of this is assuming, of course that we were somehow able to transport ourselves there in our "as is" physical state. Over time, some kind of adaptable evolution would have to occur in order to thrive. Wouldn't the same thing hold in an environment with less gravity? What would we look like? Taller? More fragile body frame?
Well DUH on my part! In the time between reading your original post and the replies, I totally forgot that's what started the discussion.
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It's got nothing to do with evolution. The weaker bones of Astronauts are the same as a person who excercises daily having stronger muscles.
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Sounds made up...
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Evolution works through natural selection. It doesn't work in one individuals lifetime, only generational. Only if your DNA was mutated, by radioactivity for instance, therefore passed down to your offspring, could you call it evolution, but as we all know 99% of all mutation is fatal. What you are talking about is Lamarkian evolution, where the traits that the parents aquire during there lifetime are passed down to the next generations. This is a pre-Darwinian hypothesis for the process of evolution. For instance, if a male astronaut spent 20 years in a zero gravity evironment and lost all bone density, then impregnated a vacationing female space traveller (icky boneless sex) than returned to earth for the gestation, the baby would be born with the healthy dense bones of any regular earth citizen. The DNA was not mutated.
All that being said, there is some evidence for a Lamarkian-type process that can and is occurring. It has to do with how environment can turn our genes on and off in the development of the organism. Then the genes may be passed down to the offspring in the on or off position.
If popuations of humans were to spend generations in zero gravity, we would almost undoubtably be naturally selected to better fit that environment (whatever that means). It would have to do with the size of the population, but I would give it about a dozen generations at least.
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I can't think of any mechanism by which microgravity would cause genetic change. Solar radiation or something might cause a heritable mutation, but the chances of any mutation being passed to a live offspring are very slim.
When an individual is born, they embody the LIMIT of evolutionary change. Nothing that individual experiences will change their partular odds of suirvival. You are dealt your genetic hand when you are born, nothing you can do can change the cards dealt.
In the broadest sense of things, genes simply seek to replicate. It is a very hard thing to do, but from a survival standpoint we are what our genes are. Our odds of surviving to procreate and pass on our genes are based upon fittness of such genes - aspects such as fidelity (how accurate genes are passed on and fecundity (how often one reproduces) are also obvious large players.
Once an organism is born, they CANNOT evolve or change. Their genetics are what they are. We see change, due the obvious and very simple process of natural selection. Genetics provide the raw material, but the environment dictates what will survive.
Change takes place over dozens, if not thousands of genetic iterations, not in the corse of a single birth. For example, we know from the fossil record that snakes were not suddenly born from lizards lacking limbs. Rather, we see in the fossil record a slow diminishment of such limbs, limbs which are manifest today in the form of atavistic hip bones in many snake species.
I'd imagine we'd look quite different, we certainly would not be as tall.
The point to take away from this is that evolution is in many ways a form of soft determinism. IOW, there is no obvious direction to the process, but every iteration of the process impacts everty step that follows it.
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We're actually seeing various mechanisms which produce fast adaptive evolution now. It's still a new field, but it involves the "imprinting" of various genes based on external stresses. However, I doubt we'll ever have to bother with it since there isn't a whole lot of readily available resources in low gravity space, and even less in ultra-low gravity (trans-solar areas of the galaxy). If we do end up in such areas we'll likely have some kind of centrifuge set up to supply "gravity." As for low gravity base stations, there would likely be some transformation unless we come up with some kind of mechanism to make ourselves heavier which could make it easier to work and get around. Wearing weights has been suggested, though after 2020 who knows what they'll come up with.
I think that's what I was refering to as a Lamarckian-type Evolution. Sharon Moalem talks about it in a chapter of Survival of the Sickest. Very good, simple read for anyone that wants an interesting perspective on "microevolutionary" changes in the recent human history as well as survival from some common viral/parasitic perspectives.
A daughter of hope and fear, religion explains to Ignorance the nature of the unknowable. -Ambrose Bierce
This alteration of the human body in different gravitational bodies is going to be quite a problem when we start to colonize planets. If children were born on the moon, they would grow very tall, but their heart mucles would be weak, and their bones would snap like twigs. This means that people born on low gravity worlds wouldn't be able to visit the ones with higher gravity, because it would be too hard on their bodies.
This also provides a problem in space exploration. We simply must make future manned spacecraft with artificial gravity, because the astronauts' bodies would deteriorate (I think I misspelled that) during longer missions.
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