I wonder how carbon dating works in this case. My understanding is that the dating method depends on the organism interacting with the carbon in the atmosphere during its lifetime (where carbon-14 is produced by cosmic rays). The interaction stops after organism dies, after which the level of carbon-14 in its body starts to decay.
But here the whole ecosystem was supposedly isolated from the atmosphere for at least 10k years. Wouldn't all organisms, both alive and dead, just have the same (decaying) level of carbon-14 after isolation happened?
I think you have it backwards -- carbon works by some organic material not interacting with the atmosphere. Atmospheric CO2 has a relatively constant proportion of carbon-14. Once it stops interacting with the atmosphere it begins to decay and have a different proportion than atmospheric carbon.
I don't understand this response. The model of the GP comment appears to be that:
- The atmosphere has a certain level of carbon-14, and living things stay at the atmospheric level by virtue of the various processes by which they interact with the atmosphere.
- When they stop living, they also stop exchanging carbon with the atmosphere, and their carbon-14 levels change due to radioactive decay over time.
- But here, an environment was sealed off from the atmosphere while some organisms remained alive inside it. If we perform radiocarbon dating on such an organism, will we get the date at which the organism died (and stopped exchanging carbon with anything) or the date at which the environment was sealed (and everything stopped exchanging carbon with the atmosphere)?
Your comment isn't responsive to this question. To answer it, we'd need to know why the atmosphere itself has constant levels of carbon-14 instead of decaying like everything else, and whether the sealed environment would have behaved more like the atmosphere or like something else.
i think it's unlikely in this case- all the tardigrade toughness comes from entering the cryptobiotic state (extreme desiccation) while I believe all these samples were in water or ice.
At least one tardigrade has been frozen in "a block of ice for three decades", then thawed, and gone on to reproduce. A tardigrade egg in the frozen sample also thawed, hatched, and reproduced. So it's possible.
Apparently when they find themselves in an extreme environment (wet or dry?) they replace their body's water with sugar (trehalose) which doesn't crystallize and cause cellular damage when frozen.
I read the original article, and they don't know what the conditions were when they entered cryptobiotic state:
The moss sample used in the current study most probably contained, initially at least, moisture from snowmelt in early summer, since at the time of collection they were not covered by winter snow accumulation. However, the possibility of freeze-drying during 30.5 years of frozen storage cannot be discounted, and whether the animals obtained here were hydrated or dehydrated (thus in an anhydrobiotic state) before or after storage is unknown.
My understanding (I'm a bioinformaticist, not a wet lab biologist, but I've collected tardigrades and read up on them), the process occurs in very dry conditions.
However, in good faith, I did some searching and found some pages which claim that cyrobiosis (a form of cryptobiosis that occurs in wet, cold enviornments) is exploited by tardigrades. So I guess you're right.
I'm curious about those tartigrades. Will the scientists put them in the water and bring them back to life? As far as I know about tartigrades, once immersed in water, the body returns to a normal metabolic state over the course of a few hours, even though they died hundreds of years ago.
But here the whole ecosystem was supposedly isolated from the atmosphere for at least 10k years. Wouldn't all organisms, both alive and dead, just have the same (decaying) level of carbon-14 after isolation happened?
EDIT: expanded for clarity.