Something I’ve been pretty interested in for the past few weeks….geological eras, mass extinctions, and the role of climate change in anoxic events. Enjoy…not that this is very enjoyable stuff, it’s kind of icky in fact, but it is fascinating.
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If the studies mentioned in the last paragraph of this Wikipedia section are http://en.wikipedia.org/wiki/Hydrogen_sulphide#Induced_hypothermia to be taken at all seriously then you’d have expected this talk to have at least mentioned the matter.
I realise the main interest here is the geological aspects but still…
It seems a (tentative) response to those who say CO2 has been higher in the past is to point out these higher CO2 intervals also coincided with mass extinction events.
In reponse to Ed Davies’ comment it is worth noting that Mr. Ward does in fact mention the effects of low levels of hydrogen sulfide on animal metabolism and temperature regulation at the end of his talk. If you don’t believe me go to the sixteenth minute of the lecture and see for yourself.
In the wikipedia article that Ed Davies refers to there are a number of very interesting assetions. One which was startling to me is that the “recognition threshold” of hydrogen sulfide, which is the concentration at which it can be smelt, is said to be 0.0047 ppm. This concentration of hydrogen sulfide is signicantly smaller than that which personal gas detectors are set for (10 ppm), but what mechanical gas detectors are capable of versus the abilities of our sense of smell is not something I know the answer to. As a general rule what we are capable of perceiving is more than a little amazing when one takes the time to think about it. As a poison hydrogen sulfide is said to be similar in toxicity to hydrogen cyanide, and both have been used as weapons. As weapons neither of the mentioned gases were amongst the worst. There are poison gases that are even more deadly, and which are pernicious even for those fortunate enough to survive exposure. I presume it to be the case that both hydrogen sulfide and hydrogen cyanide can cause death at a similar atmospheric concentration.
Mr. Ward seems to be of the opinion that the reponse of mice and other animals to survivable levels (80 ppm) of hydrogen sulfide is evidence for an adaptive reponse to higher levels of hydrogen sulfide during or resulting from the Permian extinction event.
In the wikipedia article it is said in the section on induced hypothermia that:
hydrogen sulfide binds to cytochrome oxidase and thereby prevents oxygen from binding, which leads to the dramatic slowdown of metabolism. Animals and humans naturally produce some hydrogen sulfide in their body; researchers have proposed that the gas is used to regulate metabolic activity and body temperature, which would explain the above findings.
This is given support by the following citation: Mark B. Roth and Todd Nystul. Buying Time in Suspended Animation. Scientific American, 1 June 2005.
The question of whether the response of mice to hydrogen sulfide is to be seen as evolutionary evidence seems to me to be an open one. If the use of hydrogen sulfide to regulate metabolism and body temperature predated the Permian extinction event then the effects seen in mice could be coincidental. Nonetheless it is of interest.
Patrick R said: “In reponse to Ed Davies’ comment it is worth noting that Mr. Ward does in fact mention the effects of low levels of hydrogen sulfide on animal metabolism and temperature regulation at the end of his talk.”
Yes, indeed; that was what I was responding to. What I was pointing out, though, were the studies mentioned in the last paragraph of that Wikipedia section which seem to indicate that the reactions in small mammals don’t seem to transfer to large animals putting some doubt on the trauma treatments that Mr Ward is suggesting.
Ed,
I am sorry that I misunderstood you.
I just had another look at the wikipedia article on hydrogen sulfide. At the end of the paragraph on induced hypothermia there is a new reference to a TED talk by Mark Roth. That is to say: new to me. I assume it is a new addition, because I didn’t notice it previously. Mr. Roth describes work done in the last five years on the use of hydrogen sulfide with the goal of using it as a medical treatment. As this speaks to your concerns I believe that you would enjoy hearing what the man has to say, if you have not already heard of him.
http://www.ted.com/talks/lang/eng/mark_roth_suspended_animation.html
Enjoy