# Help Me Understand Fossils **URL:** \ **Category:** Factual Questions\ **Created:** [September 24, 2015, 1:08am UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360 "2015-09-24T01:08:57Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![UncleFred](https://avatars.discourse-cdn.com/v4/letter/u/f0a364/32.png) [@UncleFred](https://boards.straightdope.com/u/UncleFred)\ **Post date:** [September 24, 2015, 1:08am UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/1 "2015-09-24T01:08:57Z")
The news about Homo Naledi reminds me of this. I was always thought when you saw a dinosaur skeleton in a museum, you were not actually seeing bones, but seeing some sort of stone that had slowly replaced the decayed bone while still in the ground. But I often see descriptions of dinosaur ‘bones’. On the other hand I’ve seen the (much more recent) Homo Naledi find described as “fossils”, yet there is talk of extracting DNA. So what’s the Straight Dope? Are dinosaur exhibits stone or bone? If bone, has anyone extracted DNA? And what is the oldest bone of anything ever found? P.S. [Dictionary.com](http://Dictionary.com) says a fossil is “any remains, impression, or trace of a living thing of a former geologic age, as a skeleton, footprint, etc.” but that doesn’t strike me as sufficiently scientific. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [September 24, 2015, 1:49am UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/2 "2015-09-24T01:49:10Z")
> [@UncleFred](#): > > I was always thought when you saw a dinosaur skeleton in a museum, you were not actually seeing bones, but seeing some sort of stone that had slowly replaced the decayed bone while still in the ground. What you see in the museum is some sort plaster or plastic model of the original fossils. Rocks themselves are far to heavy to construct a standing skeleton of the average dinosaur. The fossils those models were constructed from are, as you say, rock that has replaced the original bone material. > [@](#): > > But I often see descriptions of dinosaur ‘bones’. Because fossils can be incredibly accurate reproductions of the original bones, even preserving microscopic detail, it is perfectly accurate to describe dinosaur bones base don fossils, even though we don’t have any of the bones. Think of it in the same way that doctor can describe your bones base don an x-ray without ever seeing the actual bone, just an image o it. > [@](#): > > On the other hand I’ve seen the (much more recent) Homo Naledi find described as “fossils”, yet there is talk of extracting DNA… > > [Dictionary.com](http://Dictionary.com) says a fossil is “any remains, impression, or trace of a living thing of a former geologic age, as a skeleton, footprint, etc.” but that doesn’t strike me as sufficiently scientific. That is an accurate scientific definition.Fossils can be casts, trackways, footprints mummies etc. There isn’t any single “type” of fossil. Even with the standard bone-stone fossilisation, the process can take many thousands of years to complete, so there isn’t a specific point at which a specimen ceases to be bone and becomes stone. That’s why you can extract DNA from more recent fossils. > [@](#): > > Are dinosaur exhibits stone or bone? Neither. They are plastic models of the original stone impression of the original bone. > [@](#): > > If bone, has anyone extracted DNA? Yep, there have been quite a [few successful attempts](http://humanorigins.si.edu/evidence/genetics/ancient-dna-and-neanderthals/neanderthal-mitochondrial-dna) to extract DNA from Neanderthal fossils, for example. And what is the oldest bone of anything ever found? The oldest bone fossil will be as old as the oldest animal with bones, which is relatively recent. There are far older fossils of shells and even soft-bodied worms, jellyfish and bacteria. ---
**Author:** ![Atamasama](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/atamasama/32/12961_2.png) [@Atamasama](https://boards.straightdope.com/u/Atamasama)\ **Post date:** [September 24, 2015, 1:56am UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/3 "2015-09-24T01:56:02Z")
Fossils are anything left behind when something living dies. It could be bone turned to stone, or actual remains preserved, or even just the impression of something left in dried mud. Usually if the stuff you find is at least 10,000 years old, it’s considered a fossil. Most organic material that old has totally decomposed so you’re finding impressions or something mineralized. But something trapped in amber can be intact enough to extract DNA (like in Jurassic Park). Other conditions might preserve a fossil enough for DNA extraction; trapped in dung, kept in certain air-tight caves, and so on. Not all fossils are totally “fossilized” (mineralized). ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 24, 2015, 2:15am UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/4 "2015-09-24T02:15:05Z")
For what it’s worth, when scientists have tried to extract DNA from mosquitoes trapped in amber, all they’ve managed to get is mosquito DNA. On the other hand, they have actually managed to recover T. rex DNA, albeit extremely fragmented and incomplete, from one fossilized bone. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [September 24, 2015, 3:41am UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/5 "2015-09-24T03:41:01Z")
I don’t know about British museums but many of the skeletons in American ones are the [real deal](http://www.carnegiemuseums.org/cmag/feature.php?id=35). > [@](#): > > What separates the really great dinosaur exhibits from all the rest? Real dinosaur skeletons. And with a collection of real dinosaurs surpassed only by the Smithsonian and New York’s American Museum of Natural History—and, soon, the only dinosaurs to be reassembled in active poses within painstakingly constructed, scientifically accurate environments—Carnegie Museum of Natural History’s new dinosaur exhibit will be in a league and a setting all its own. > > Matt Lamanna doesn’t like to count. Dinosaur bones, that is. Neither do many of his peers at some of the world’s most prestigious natural history museums. But when phase-one of Dinosaurs in Their Time opens November 21 [2007], the world will be counting—and wondering, “Are all those dinosaur bones real?” > > The answer: Of the 19 free-standing dinosaur skeletons that will appear to be roaming the halls of Dinosaurs in Their Time, 15 will be the real deal (except for occasional filler bones, made from casts or sculpted pieces, here and there). ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [September 24, 2015, 4:39am UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/6 "2015-09-24T04:39:33Z")
> [@Blake](#): > > Neither. They are plastic models of the original stone impression of the original bone. Depends on the display, but as **Exapno** says, many mounted skeletons contain real fossils rather than replicas. For example, [85% of the display skeletons at the American Museum of Natural History contain real fossil material.](http://dinosaurs.about.com/od/dinosaurmuseums/p/amnh.htm) Older mounted skeletons might have some bones replaced by plaster. On newer ones replacement bones tend to be made of resin. This goes for the large mounted skeletons. Other display material such as skulls, smaller fossils, and fossils that are displayed still in the original matrix are even more likely to be real fossils. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [September 24, 2015, 6:11am UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/7 "2015-09-24T06:11:01Z")
Not all dinosaur fossils are completely turned to stone. They have found some soft tissue in dinosaur bones, including things like [collagen fiber and red blood cells](http://www.natureworldnews.com/articles/15094/20150609/soft-tissue-found-in-dinosaur-fossils.htm). ---
**Author:** ![Anaglyph](https://avatars.discourse-cdn.com/v4/letter/a/ed8c4c/32.png) [@Anaglyph](https://boards.straightdope.com/u/Anaglyph)\ **Post date:** [September 24, 2015, 6:40am UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/8 "2015-09-24T06:40:30Z")
Here is a [nice overview](http://www.fossilmuseum.net/fossilrecord/fossilization/fossilization.htm) of the different processes that form fossils ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [September 24, 2015, 11:18am UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/9 "2015-09-24T11:18:52Z")
In the old CRetaceous Dinosaur display on the 4th floor of the American Museum of Natural Histoiry, the skull of the T. Rex was always a cast. But you knew this because the original was in a glass case by the side of the skeleton. It was far too valuable a specimen to mount way up there, where it might fall and get broken. You can understand why museums might be reluctant to actually mount the fossil bones – not only are they heavy, requiring ingenious metal bracing to hold them while being unobtrusive, but any drilling through the fossils to attach them to this rigging will remove a valuable piece of the fossil (and new reasons to look at all parts are constantly emerging), and it would only be in the service of aesthetics. In newer fossil mounts, there are other reasons for not using the actual bones. One reason that T’ Rex skull was replaced by a cast is that it’s slightly (but only slightly) “crushed”. But the skull of the “Sue” T. Rex was REALLY crushed. Scanning of the fossil and computer reconstruction allowed the visualization of the original state of the skull, which could be 3D printed and substituted. That sort of thing has other uses. Dinosaur skeletons aren’t always complete – something that lead to them putting a Camarasaur skull on the American Museum of Natural History’s Brontosaur (Apatosaur) skeleton. As in that case, they usually use a bone from another skeleton. But what if it’s not the right size? Dinosaur skeletons are rare enough, and individual specimens are of different ages and sizes. At the Smithsonian, they replaced some of the missing bones in a Triceratops skeleton with ones “adapted” from another specimen, which was smaller. Again, they were able to scan the bone, adjust the size in the computer, and print out a model that was the correct size. ---
**Author:** ![Broomstick](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/broomstick/32/246_2.png) [@Broomstick](https://boards.straightdope.com/u/Broomstick)\ **Post date:** [September 24, 2015, 12:41pm UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/10 "2015-09-24T12:41:21Z")
> [@Blake](#): > > What you see in the museum is some sort plaster or plastic model of the original fossils. Rocks themselves are far to heavy to construct a standing skeleton of the average dinosaur. Not always the case. There are some instances where the extra effort/expense is spent to display the actual fossil. Sue the Tyrannosaurus Rex in the Chicago Field Museum, for example, is mostly her actual fossil, with synthetic bits used only for missing pieces and her skull (which is a cast of the original). Her skull fossil is on separate display. The reason this was done is because Sue is not only the largest \*T. Rex \*found so far, but also an unusually complete skeleton (replacements for the missing pieces are a different color than the fossil, so you can tell which is which). So, while a lot of skeletons on display in museums are copies of fossils, some are the real thing. ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [September 24, 2015, 1:52pm UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/11 "2015-09-24T13:52:04Z")
> [@UncleFred](#): > > And what is the oldest bone of anything ever found? The [oldest fossils](https://en.wikipedia.org/wiki/Ediacara_biota) (of multicellular creatures) ever found are from the Edicarian range in Australia and are about 600 million years old, but they’re all invertebrates so no bones. ---
**Author:** ![Canadjun](https://avatars.discourse-cdn.com/v4/letter/c/76d3ee/32.png) [@Canadjun](https://boards.straightdope.com/u/Canadjun)\ **Post date:** [September 24, 2015, 2:26pm UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/12 "2015-09-24T14:26:08Z")
> [@Chronos](#): > > For what it’s worth, when scientists have tried to extract DNA from mosquitoes trapped in amber, all they’ve managed to get is mosquito DNA. 😕😕 So you are saying they only managed to get what they wanted to get? ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [September 24, 2015, 2:27pm UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/13 "2015-09-24T14:27:20Z")
No, they wanted to get DNA from the blood (of other animals) that would hopefully still be in the mosquitoes’ digestive tracts. Did you not see/read _Jurassic Park_? But there wasn’t any, or it was too degraded. ---
**Author:** ![Canadjun](https://avatars.discourse-cdn.com/v4/letter/c/76d3ee/32.png) [@Canadjun](https://boards.straightdope.com/u/Canadjun)\ **Post date:** [September 24, 2015, 2:50pm UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/14 "2015-09-24T14:50:59Z")
> [@Really\_Not\_All\_That\_Bright](#): > > Did you not see/read _Jurassic Park_? Actually, no I have never had the pleasure of seeing/reading Jurassic Park, so it took me a few minutes to realize what you were getting at. By the time it “clicked” the 5 minute edit window was up, so I just left it. :smack: ---
**Author:** ![D18](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@D18](https://boards.straightdope.com/u/D18)\ **Post date:** [September 24, 2015, 3:03pm UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/15 "2015-09-24T15:03:59Z")
> [@Chronos](#): > > For what it’s worth, when scientists have tried to extract DNA from mosquitoes trapped in amber, all they’ve managed to get is mosquito DNA. > > On the other hand, they have actually managed to recover T. rex DNA, albeit extremely fragmented and incomplete, from one fossilized bone. Are you saying that DNA can be recovered even from a mineralized/petrified/whatever the right word is bone? ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [September 24, 2015, 3:06pm UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/16 "2015-09-24T15:06:27Z")
I highly recommend a trip to the [Carnegie Museum](http://www.scified.com/topic/37343&page=2) to see the dinosaurs there, BTW. The display is breathtaking. The pictures are fine but don’t do it justice. You need to stand beside the bulk to viscerally feel their stature in the world. ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [September 24, 2015, 3:12pm UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/17 "2015-09-24T15:12:01Z")
What’s the crocodilian thing halfway down the page? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 24, 2015, 3:14pm UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/18 "2015-09-24T15:14:17Z")
> [@](#): > > Are you saying that DNA can be recovered even from a mineralized/petrified/whatever the right word is bone? Well, I won’t say absolutely that it can’t be, but in this case, what actually happened was that a small amount of bone in the middle of the fossil wasn’t completely petrified. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [September 24, 2015, 8:59pm UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/19 "2015-09-24T20:59:43Z")
> [@Chronos](#): > > On the other hand, they have actually managed to recover T. rex DNA, albeit extremely fragmented and incomplete, from one fossilized bone. I’ve seen reports of collagen recovered from what appeared to be blood tissue, but as far as I’ve been aware, no report of dinosaur DNA recovery has panned out. Do you happen to have a cite? I’d like to be aware if it has happened. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [September 24, 2015, 9:52pm UTC](https://boards.straightdope.com/t/help-me-understand-fossils/732360/20 "2015-09-24T21:52:58Z")
> [@Really\_Not\_All\_That\_Bright](#): > > What’s the crocodilian thing halfway down the page? [_Redondosaurus_,](https://en.wikipedia.org/wiki/Redondasaurus) a phytosaur. [Phytosaurs](https://en.wikipedia.org/wiki/Phytosaur) resembled crocodilians but were not directly related. [Next page](https://boards.straightdope.com/t/help-me-understand-fossils/732360.md?page=2)