• The short-beaked echidna is the only mammal that has been completely frozen and subsequently revived.

I remember reading a while back (a few months) that there was a dog that was frozen and then brought back to life. I beleive it was on a credible scientific website, but I can't seem to find the article or any information on it. If I remember correctly they said that they drained the dogs blood and replaced it with some type of anti-freeze. After it was frozen the anti-freeze was drained and the blood was replaced and the dogbrought back to life. I know there was more to it than that thought. Can anyone else possibly find this article?

First, and this isn't directed at you, but just pointing it out for the viewing audience at home, many animals can be completely frozen and revived by completely natural means. This is a fact of life for many fish and amphibians during the winter months. However, for mammals, which are warm-blooded, it's a completely different matter.

There have also been a number of mammals that have been crygenically frozen and revived, such as that dog you mention. But it's not limited to just dogs, it's been done with a number of mammals, such as mice, rats, rabbits, cats, and so on. But the methods there are artificial. It of course suggests that such a thing will be possible for humans at some point.

The wonderful thing about the short-beaked echidna is that it can be frozen and revived without any artificial means. The most interesting part about this is that the animal is native to the Australian desert, so who would really expect that it would have such an odd ability that no other mammal seems to possess?

Apparently, this was discovered by accident by a professor of zoology named Lyn Selwood at the University of Melbourne. As the story goes, she discovered the echidna in her deep freezer one Monday, and since it had been unused since the previous Friday, the echidna had been in there for at least 60 hours. She reasonably figured that the ill-fated exploratory critter was a goner, and so had placed it in the bio-waste bin in her lab. Later that day, she heard something in the bin, opened it up carefully -- expecting a rat -- but discovered that the echidna was alive! She apparently did a bit of experimentation on its ability, but didn't want to outright kill any echidnas (since they are a semi-protected species), so she froze it again, this time for 100 hours, and it revived again after a number of hours at room temperature. She apparently felt a bit guilty after that and released it back into the desert.

I'm just shocked that an echidna would have this ability -- surely it never has such a need to use it in its current habitat. I personally suspect that perhaps the echidna evolved this ability when Austrailia had a much colder climate and so it would go into deep-freeze each summer (instead of hibernating). It begs the question of what other mammals might be able to do this. If my theory is correct, then that implies their perhaps all marsupials would share this trait, but it would clearly be immoral to research that just on a lark.

Apparently it is possible to revive a mammal from a frozen state, but the way in which it needs to be thawed is extremely difficult. Recovering DNA is not a problem, but reviving the complete animal is very tricky to achieve because the thawing process needs to be uniform across most areas of the body except a few key places and then once the liquids begin to melt the remaining frozen parts need to be thawed quickly to prevent degenerative chemical processes occuring (eg brain damage) and the heart needs to be restarted. The echidna was possible due to it's small size and relatively uncomplicated chemical and physical structure - still I would be surprised if it escaped with it's brain intact.

Interesting area of science and still much to be learnt :) Go humans!

I recently saw it on another show. It's called a grey tree frog.

A frog has a less centralized nervous system than mammals, and the fact it's amphibious greatly helps recovery from freezing (it has two different methods of retrieving oxygen).
Mammals must have nearly every major organ restored at approximately the same time in order to recover successfully. But, marsupials have a "direct route" to the outside via their pouch. This may be why the echidna can be thawed successfully. I mean, if humans didn't have to breathe but could perform oxygen transfer via some other method, they could also recover. At least, that's my theory.

When I was in college I worked summers on a Highway crew. (OK -- maybe 'worked' isn't the right verb.) For kicks these guys would catch a regular ol' housefly and stick it in a glass of water and hold it under until it stopped moving. They'd leave it in the water for a while -- the longest I saw was about 4 days -- and then they'd take the fly out, put it on the table and cover it with tablesalt. After a few minutes they'd blow the salt away and *every* time the fly flew away. Don't know what the physiological explanation of that is.