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We've found all sorts of interesting stuff in arctic ice & permafrost around the world.

Bacteria & the like far older than the more media friendly mammoth specimens have been found, living bacteria has been found in ice cores as old as 420,000 years.

Obviously I'm not thinking about living specimens.

The ebb & flow of the ice & permafrost through our various ice ages are probably a factor in what might plausibly have survived unthawed to be found & by extension where (not all dinosaurs lived exclusively in warm climates) & when any particular species was found.

So is a frozen dinosaur in any way plausible, how about a neanderthal?

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    $\begingroup$ It may also benefit you to look at dry preservation, most of the Neanderthal DNA we have comes from extremely desiccating environments. $\endgroup$
    – Ash
    Feb 25, 2019 at 14:36
  • $\begingroup$ @Ash Hmm.. so the full monty version of this enterprise likely has 3 specialist departments then ~ for storage (handling & dna extraction etc) of frozen, dry & amber samples. $\endgroup$
    – Pelinore
    Feb 25, 2019 at 16:34
  • $\begingroup$ DNA has been extracted from extremely ancient insects in amber,so if you are only interested in bringing back insects you can go back to the Carboniferous. $\endgroup$
    – John
    Feb 25, 2019 at 17:05
  • $\begingroup$ Encino Man had a Neanderthal frozen. Not sure if that was Hard Science, though. $\endgroup$
    – Hannover Fist
    Feb 25, 2019 at 22:56

8 Answers 8

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Permanent ice caps have not been a constant during Earth history. For example we know that in the past the poles were free from ice.

Therefore the oldest possible frozen sample is as old as the oldest permanent ice caps or frozen terrain on Earth. Anything that got frozen before that time has been thawed in the meantime.

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  • $\begingroup$ Damn good point, guess I was wrong about that being a question for another day, it actually goes to the core of the question.. hmm, the question may need a rejig, or that might just be the answer ~ 35 million years ago was the last time the ice caps weren't there. $\endgroup$
    – Pelinore
    Feb 25, 2019 at 13:20
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    $\begingroup$ Dinasaurs are off the table then ~ they went extinct 65 million years ago, neanderthals are a mere 40 thousand years ago so they're plausible. $\endgroup$
    – Pelinore
    Feb 25, 2019 at 13:27
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    $\begingroup$ @Pelinore: The Antarctic ice sheet formed about 35 to 45 million years ago. The Greenland ice cap is less than 20 million years old. Anyway, the Mesozoic ended 66 mya, so neither ice sheet can contain frozen non-avian dinosaurs. $\endgroup$
    – AlexP
    Feb 25, 2019 at 13:28
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    $\begingroup$ @Pelinore its still possible for neanderthal, that range is just our best estimate based on fossil and artifact remains, of course, it will not preclude the random lost straggler. It will be an earlier neanderthal though the ice cap maximum would have kept them too far from existing ice caps. $\endgroup$
    – John
    Feb 25, 2019 at 13:53
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    $\begingroup$ @John, amber does not qualify for frozen sample, as per OP's question $\endgroup$
    – L.Dutch ♦
    Feb 25, 2019 at 17:34
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The oldest frozen specimens would likely be roughly 15-30 million years old and would be whatever critters were on Antarctica during the Oligocene or early Miocene.

Around that time, Antarctica finished its split from other land masses with the opening of the Drake Passage between it and South America, allowing the Antarctic Circumpolar Current to begin keeping warmer waters away and permanently freezing the continent into what we know today.

Until it fully froze, conifer forests and steppes covered the continent, and if Antarctic fauna were anything like the rest of the world it was dominated by a mix of critters that were vaguely similar to today's large mammals, rodents, and sea life.

So, it looks like your frozen Oligocene Park will probably be decorated with odd-looking pine trees, and be filled with horses and mice with weird snouts. Not as awe-inspiring as a T-Rex, but still pretty cool.

As for finding frozen Neanderthals, it's possible but unlikely. In order to be found frozen, they would have needed to die in an area of permafrost that has been unchanged for the last 40-50,000 years, and their known range doesn't have many options for that. However, we did find a 5,000 year old mummy frozen in the Alps, so anything's possible.

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    $\begingroup$ Skimming the images produced by a oligocene animals Google search I think I could live with that :) $\endgroup$
    – Pelinore
    Feb 25, 2019 at 14:13
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    $\begingroup$ @Pelinore: I'd imagine visiting Oligocene Park would give roughly the same feeling of the early explorers of Australia. $\endgroup$
    – Giter
    Feb 25, 2019 at 14:21
  • $\begingroup$ Here's (perhaps) the nearest thing to us from back then. $\endgroup$
    – Pelinore
    Feb 25, 2019 at 15:19
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    $\begingroup$ its still possible for neanderthal, that range is just our best estimate based on fossil and artifact remains, of course, it will not preclude the random lost stragglers. The expanding ice sheets would erase much of the evidence for their presence further north prior to the glacial maximum. It will be an earlier neanderthal though as they would have ot be from before the glacial maximum. Its a low chance but not impossible. $\endgroup$
    – John
    Feb 25, 2019 at 17:11
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a study published this week (October 10 [2012]) in the Proceedings of the Royal Society B estimates that DNA from bone has a half-life of 521 years

(Link)

That's the rate the DNA molecules spontaneously fall apart. This study does not address DNA in tissue other than bone, or how freezing temperature affects the deterioration of DNA, but I think it's still a decent estimate to start from.

How good is your technology at reconstructing DNA from teeny fragments in trillions of cells? Neaderthals went extinct 35,000 years ago. After that long (~67 half life periods) only 1/147573950000000000000th of the DNA will be left. The article sets 1.5 million years as the point after which DNA strands are too short to be read, but the point at which you can no longer recreate the whole genome might be much shorter than that.

If your technology were impossibly perfectly accurate, you might be able to approach the 1.5 million year limit.

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  • $\begingroup$ "How good is your technology at reconstructing DNA from teeny fragments" : I would have hoped to go for real world near future (so maybe 40 years more) for a sheen of plausibility ~ but applied (or set in) the very near future (so no more than 10 years from now) $\endgroup$
    – Pelinore
    Feb 25, 2019 at 17:34
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    $\begingroup$ This answer seems flawed in its assumptions. We're impressively good at reassembling broken DNA. In fact, a well-known technique is known as shotgun sequencing for its use of many small DNA fragments. This is way beyond the point where biological mechanisms can repair the damage. Furthermore, the "67 half-lives" logic appears to assume that both halves of a broken DNA string are equally likely to break in the next 521 years. However, they're on average half as short. In other words, after 67 half-lives, you expect 67 breaks in the chromosome, not 2^67 $\endgroup$
    – MSalters
    Feb 25, 2019 at 18:10
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    $\begingroup$ @Chronocidal: Are you saying that the nucleotide itself decays? As in, an adenine molecule breaking in two? That would be strange; the internal bonds are pretty strong. As far as I can tell, the chief mechanism of DNA degradation is that the chain breaks between two nucleotides. Don't forget, half-life is a nuclear concept. Atomic nuclei do break in two, and do so independently of each other. DNA chain breaks are not isolated events; the chance of that is linear in the chain length. $\endgroup$
    – MSalters
    Feb 26, 2019 at 11:34
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    $\begingroup$ @MSalters From the article "DNA from bone has a half-life of 521 years: after that amount of time, half of the nucleotide bonds that hold it together are broken [...] Based on their calculations, the team predicted that even under perfect conditions for DNA preservation, it would take a maximum of 6.8 million years for every bond to be destroyed." - So it seems you are partially right: It is the bonds that are breaking, not the acids itself - but after 500 years half of all bonds are broken (so it is not split in two, but into a lot of pieces). $\endgroup$
    – Falco
    Feb 26, 2019 at 12:14
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    $\begingroup$ @Luke - the original paper describes microbiological activities and bacteria as the most prevalent factors and cite an average storage temperature of 13°C for the samples. I don't know if this half life has any merit for a storage far below 0°C where the microbiological activities should come to a stop... $\endgroup$
    – Falco
    Feb 26, 2019 at 12:34
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With a well preserved bone less than a million years old, you can do anything you want.

Samples from a horse leg bone more than 700,000 years old have yielded the oldest full genome known to date.

The six-inch (15-centimeter) horse leg bone the team analyzed originated in the Yukon Territory of western Canada. Permafrost kept the remains in a kind of cold storage for about 735,000 years until scientists dug it out in 2003.

– World's Oldest Genome Sequenced From 700,000-Year-Old Horse DNA, National Geographic

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We have the actual example of the Ice Man -- beaker culture neolithic discovered in the Alps. He was about 9000 years old.

So that can set some parameters:

Hunter or band traveling across and icefield that is in a pocket between multiple peaks. Dies in late fall. Exceptional snowfall period, so is buried under permanent snow cover which as the ice builds up puts him deeper.

Because it's a basin, the ice there doesn't move. When the ice builds up in thickness, there is a shear plane above it. Can't have glaciers feeding into the bowl either. So take a bowl that is surrounded by steep peaks that can avalanche into the bowl, but not form glaciers. Eventually the ice gets thick enough that it is above the bowl, and the excess flows off.

I think the Columbia Icefield on the border between Alberta and BC fits these criteria.

To me this would be a plausible event going back to the start of the last ice age. This would get you back to somewhere between 115,000 and 22,000 years ago.
Last Glacial Period -- Wikipedia For the longer period, you need to have some glaciation through the short inter-glacials. A mountain based shield would meet this requirement.

If you want a story line, "My father's father said that he knew a hunter who had crossed The Pass of the Winds." But in the hundred years since the cooling climate has created a permanent snowfield there.

Much of Antarctica is under water. Strip off the ice, and you have substantial inland seas. Antarctica without ice You could have various things trapped by glaciers closing off the openings. I don't know to what extent these levels freeze down. If there were hollows above the then present sea level you could trap land animals as described above. This could plausibly take you back to the beginning of the Antarctic ice cap something like 40 Megayear ago. I suspect that the timing of that is vague, so you might plausibly extend it back some. Dig into Antarctic paleo climate.

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  • $\begingroup$ Thanks, this answer should have got a bit more love than it did, the deep bowl or hole is a useful comment that helps with the possibility of potentially older ice than any ice cores recovered to date. $\endgroup$
    – Pelinore
    Sep 26, 2021 at 10:45
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It is an extreme long shot but it might be possible, some day. Not really frozen however. The extreme desiccating effects of amber has been shown to preserve DNA, even in specimens of the right time period. And at least one fragment of a dinosaur flesh has been found preserved in amber. Several feathers are also known to exist.

The problems are three fold, not every piece of amber preserves DNA in fact most do not, and dinosaur material in amber are extremely rare, even by normal amber preservation standards. Lastly the DNA is extremely fragmentary so you are talking about massive reconstruction, to the point that said organism would be more invented than restored. It would also be the single largest and most complex genomic reconstruction in history, to the point you really would need a much better understanding of genomics and biochemistry than we have now. The only thing you have working for you is phylogenetic bracketing, and the fact said dinosaurs would be closely related to the ancestors of birds. In fact they would likely get more from reverse engineering proteins in the preserved specimen which survive much better, than the DNA, but that is an even more advanced technique.

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An even more extreme possibility (very unlikely, something like winning the lottery 3000-4000 times in a row).

Per this article, it is possible that ejecta after an impact from an asteroid could reach the space (even falling onto other planets). So, in case of a huge impact, a a rock sent into the space could countain some specimen (even a piece of a dinosaur, not necessarily a complete one).
In the space, it should not decompose, so it could remain preserved, inside an asteroid in orbit around the Earth or somewhere in the outer space, until our days, where it could be retrieved by a space probe.

Of course there are many issues to address (if you plan to write a novel, you would need some handwavium for them).
In the impact it is likely that the organic matter would be carbonized by the heat.
Such a specimen could be found only by chance, there is no way to detect it.
Moreover (and most important), in the space there would be no decomposition, but cosmic rays would rapidly degrade the DNA of the specimen; even if it could find itself inside the rock, probably this couldn't provide enough shielding to allow the DNA to survive up to 65 milions of years.

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  • $\begingroup$ A nice idea but it's handwavium requirements go a bit beyond my budgeted allowance for the stuff :) $\endgroup$
    – Pelinore
    Feb 26, 2019 at 16:53
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The oldest known/recovered ice core so far is 2.7 million years old. It was pulled from Antarctica's Allan Hills area in 2015, which was coastal at the time the ice formed. Unfortunately the only animal specimens you'd be likely to recover from this site from this time would be marine lifeforms not too different from today's, as the continent had been cut off from South America for ~20-40 million years with the opening of the Drake Passage, which plunged the continent into the icy cold in the late-Miocene.

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  • $\begingroup$ I think it's nearer 8 million years now for the oldest recovered ice cores, I'd have to go check article dates to know if it was when you answered though :) $\endgroup$
    – Pelinore
    Sep 26, 2021 at 10:46

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