Question for Forensic Anthropologists!
February 5, 2014 12:46 PM   Subscribe

I'm curious to learn about human decomposition rates and wanted know: how long would it take for a human child's skeleton vs. a human adult's skeleton to dissolve in acid peaty soil? What about in soil us humans interact with everyday? (i.e. public park soil, garden soil) Thank you! Also, if anyone knows the answer, if you could please explain to me where/how you got the information :)
posted by jujube123 to Science & Nature (11 answers total) 6 users marked this as a favorite
Is this a trick question? Skeletons don't dissolve.
posted by jessamyn at 1:00 PM on February 5, 2014 [2 favorites]

According to that esteemed resource, wikipedia, bones will disolve in sphagnum (peate) moss. But I don't know how long it takes.
posted by Kerasia at 1:18 PM on February 5, 2014

How young of a child? Babies and toddlers aren't actually very bony, more cartilaginous like sharks.
posted by mskyle at 1:19 PM on February 5, 2014 [1 favorite]

In a peat bog the bones will dissolve due to the mysterious workings of sphagnum moss but in fact the flesh and "meaty" bits will be preserved as the acidic soil slows down the workings of rot causing microorgansims. So if you are trying to get rid of a body the flesh etc would have to be removed elsewhere first. I saw a special on "Bog Bodies" found in peat bogs in the UK on TV, a quick wikipedia brings up this.
posted by wwax at 1:28 PM on February 5, 2014

Acid peaty soil? I would guess something in excess of 10,000 years, though perhaps that's an outlier.
posted by pont at 1:29 PM on February 5, 2014

I previously answered a similar questio; there's another comment above it regarding a recent skeletal find in New England on the town green.

I would expect a healthy adult in peak age and physical condition (not an older person, or someone who had other reasons to have bone loss, like chronic illness or long-term use of certain medications) to endure longer simply due to the physical amount of bone mass. The same with the child - smaller children = smaller bones = easier to decompose.

Skeletons will eventually dissolve but let me tell you, the spongy intermediate period (~300 years in coastal CT) is really off putting and fragmented remains may not be identifiable to the layperson.

Absolutely depends on actual condition of the soil. Peaty soil, like others say, is different than acidic non-peaty soil. I don't have experience with peat.
posted by cobaltnine at 1:29 PM on February 5, 2014 [1 favorite]

Regarding an adult's remains in peat bog-type soil; they may be preserved for a long damn time. Check out The Life and Death of a Druid Prince.
posted by cog_nate at 1:39 PM on February 5, 2014

I'm not sure of the exact difference but acid does impact preservation. You might find this article and its bibliography helpful-- it talks about bone size and different soil types.
posted by jetlagaddict at 2:25 PM on February 5, 2014

And this book, Biological Anthropology of the Human Skeleton. Especially the section on the preservation of human bone. You could also try writing some of the more active osteological blog writers though admittedly they might want more information about the situation and the actual soil involved. If you have a specific area in mind, it should also be possible to look up forensic/archaeological reports from there to see how actual bone finds have been preserved.
posted by jetlagaddict at 2:31 PM on February 5, 2014

Yeah, I'm an archaeologist and there is no single answer to this question. In certain wetland environments flesh can last for a long time. At Monte Verde in Chile, there is preseved mastodon meat (with cut marks) and mastodon leather from 14,000 years ago. Yet many wetland sites do not preserve skin and flesh in this manner at all. Factors like temperature, anoxic groundwater, anaerobic deposition conditions (encased in clay, for example), pH, presence of tannic acid, etc. would all influence preservation.

The famous European bog bodies tend to have tanned skin, excellent preservation of internal organs and of hair and fingernails, and yet be completely devoid of any bony structure -- they are really floppy.

For a body buried in a typical temperate forest soil underlying conifers (think west coast) with no other influences and not in a coffin, and reasonably well drained, then my best guess would be the flesh would be gone within three years and the bones would be gone within a century. This is mainly because the soils here are slightly acidic because of the formation of carbonic acid as the rain interacts with decaying vegetation (so I am told). Bacteria eat the flesh and the acid eats the bones or at least degrades them and opens them up for microbes to eat the non-mineral component.

Other vegetation covers and soil types could change this dramatically though I suspect in most cases preservation would be longer, NW coast soils are some of the most preservation-hostile ones around.

For example, the presence of a lot of shell at an archaeological site sets up an alkaline micro-environment which buffers the acidity and so bone lasts indefinitely, but skin and flesh do not.

Anyway, the answer to your question is, "it varies. a lot".
posted by Rumple at 2:42 PM on February 5, 2014 [5 favorites]

For a layman-friendly idea of what forensic anthropologists do (and do not yet) know about how the human body decomposes under different conditions, try the book Death's Acre.

It's the story of the founding of the U.S.'s first body farm at the University of Tennessee in Knoxville, and of some of the cases the farm's staff have been involved in, co-written by the man who started it.
posted by soundguy99 at 8:14 PM on February 5, 2014

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