How long does it take bones to decay? Above Ground, Inside, Humid Environment

Question

From death to brittleness?

Two bodies, on a bed, in an embrace. Windows and doors closed, so little to no air and light, but not completely air/light tight. No scavenger animals/rodents, but bugs would obviously be present. Humid (tropical rain-forest) environment.

The aim is to have my characters stumble across this old castle, and find the bones of two people on the bed. I don't care if the bones are touched they would fall to dust, or if they are moved slightly/disturbed by bugs, or even if some of the bones are dust already, as long as it can be made out that its two skeletons embraced together. (and if not clearly embraced, its at least clear that its two skeletons)

(i know "dust" isn't the appropriate term here, but you get what I mean?)

How many years could this take? Thankyou

EDIT: Just wanted to re-iterate, I don't so much care about the decomposing bodily fluids and flesh. I know that will decompose and be eaten by bugs and will stain the sheets upon decomposition.

I know that mummification is out, as of the humidity.

I'm wanting to know what happens to the BONES well after the process of rotting flesh is done. I know the joints wont stay together, and I know that the bugs will move the bones around a bit if they are eating the flesh. But say that, after a month or so of the people being dead, their bones would still be on the bed, and it would be obvious that two people were on the bed together, even if not embracing? how long would it take before their bones became so fragile and brittle that they would turn to "dust." or upon discovery of the bones, and disturbing the bones, would they disintegrate to dust upon a rush or air or a touch of hand?

Answer 1

Okay, there's not much data on timescales of human bones decaying away to nothing, because we bury/ cremate our dead. Also when folk come across a pile of bones, they tend to phone the police. So you might have to look at studies of animal bones and extrapolate from that. The search term you'll need is taphonomy. That's the science of death and decay (and fossilisation).

The stages of bone decay are as follows. This scale was invented by Dr Clive Trueman and is based on British chocolates and biscuits, so apologies to those not familiar with them.

1. Fresh bone. The bone is just like one you get from the butcher's for your dog.
2. The Crunchie. The bone has dried out but still has a smooth outer cortex. If you split it open it has a 'honeycomb' cellular structure, like in life.
3. The Ripple. The bone still looks normal from the outside, with the outer cortex still intact. However, inside it is starting to recrystallise.
4. The Flake. The outer cortex has gone and the recrystallisation is complete. The bone has a crumbly texture and will fall to pieces if you pick it up or handle it roughly.
5. The soggy digestive biscuit. The bone is reduced to lumps of mush.
6. Only a chemical analysis of the soil it was lying on can now detect that the bone was there at all.

Not the same environment as your bones, but animal bones in Amboseli National Park decayed beyond recognition in 10 to 15 years. These bones are out in the open air. I'd say that's the fast end of the scale for bone disappearance.

Here's another paper where bones in Amboselli are there for at least 26 to 40 years.

This paper on bone decay in different environments looks as if it has useful data, but you'll have to pay to get beyond the abstract.

So, your case has humidity, which will speed bone decay as fungi and bacteria get at them, but is indoors, so it won't be as fast as the Amboseli examples. If it is tropical rainforest climate humidity things will decay a lot faster than cold, damp UK humidity.

Given that there are caves full of ice age cave bear bones, your skeletons can survive for thousands of years if you want them to. Or crumble if that fits the story better.

Answer 2

Not as long as you might think, especially if the room is not tightly sealed. Bugs will eat a corpse pretty efficiently, even without animals.

If you are looking for this to be some romantic scene because there isn't viscera, well, it's going to smell if it's been sealed, no matter what. Even if they are bones. The bed will be stained with the fluids of their bodies as well. Mummification might actually be better, but won't work if it's humid/not sealed tightly.

The problem with bones is this: once flesh falls away, bones fall apart. They hold together when buried, because they are held together by the earth itself, but in the conditions you are talking about, the jaw bone generally falls away from the skull.

Here are the factors you will need to consider, because these data points are crucial, and you can't get an answer without them:

Humidity The higher the humidity, the less likely the corpses will mummify.

Temperature Are there seasons? Is this a tropical area? The season in which they die will be a crucial factor.

In high humidity and temperature, they can be reduced to bone in a matter of weeks with insects around. If any rats/small critters can get in, the hands and feet will likely be gone. And if there is any airflow at all, rats/critters will be highly motivated. I think, if you are going for romance, which is what it sounds like and you want realism, so I'd say--seal it tight to make some mummies. Mummies rule! Skeletons just can't keep it together! ;)

Answer 3

They discovered Richard III's bones a few years ago. Given that he died in 1485, bones do survive for around 5 centuries in soil.

Flesh rots in air, bones desiccate. From what a quick Google search indicates, bones become powdery in air in around 50 years. That said, I would guess, given a lack of air movement, and no animals crushing them with their weight/gnawing on them, the bones should retain their shape indefinitely.

Answer 4

It really depends on four things

1. how well sealed the room is, keeping rodents out is essential, they will eat bone just for the calcium.

2. the humidity, fungi can eat bone so you want it dry, light is likewise the enemy.

3. the temprature, if it is exposed to freezing and thawing the bones will powderize quite quickly. so it needs to be consistently above freezing or consistently below, dryness will also help.

4. how much anatomy the people finding them know, the more anatomy they know the worse off the bones can be.

As long as only bacteria or small insects can get to it bones, and it is dry they may survive intact (identifiable) for 300 years as long as they do not go through to many freeze/thaw cycles. basically the better the conditions are for natural mummification the better they are for your bones.

Your biggest problem is the tropical rain forest, the bones are gone unless they get buried, heck even your buildings are not going to survive that well in that environment. Bones a month sure, a hundred years highly unlikely. The more cave like the place they are they better they will survive in that climate.

There is one way to preserve the bones, but they will not be easy to find afterwards. Guano can seal and preserve material in a similar fashion to amber, but you need to keep it away from the sun and it needs to build up quickly. so you need a lot of bats, possibly coming in through a hole in the roof to keep the rodent population non-existent and keep out the most destructive insects (ants and termites), for this same reason your building needs to be big. The downside is that your bones will then be buried, so unless your people are looking for them they will not find them.

bones turning to dust requires a very dry environment, you need to keep biological activity to a minimum. I have handled fossilized mammoth bones in Wyoming and you could crush them with your hands and they were constantly flaking off bone. They were buried in almost 3 feet of natron soil in an extremely dry environment.

Answer 5

The rule of thumb is “100 degree-days to get bones”. I don't know what degree is measured from, but that should be a start for Google…

And that turns up this link which is a start. This one, The Rate of Decay in a Corpse is more informative and provides the vocabulary you will need for further searching.

Just skimming, the lack of rain or direct exposure and not being directly connected to the soil will reduce the decay rate. Depending on conditions you may bet a mummy and not a skelleton.

So allow for rats or other wildlife to get in from a wooded area, as well as flys and beetles. That's the opposite of what you specified, so you can expect dessicated remains with nothing happening after flys. You might postulate specific carnivorous beetles, but really you wrote yourself into a corner. Where would the flesh hqve gone off to?