[MUSIC] [MUSIC] Ultimately the body is going to turn into a skeleton, and once it's a skeleton, it's very difficult to get good information, because bones, after all, are bones. One test that can be done is to look at fluorescence. Fresh bone will fluoresce under UV light. Old bone, maybe more than a hundred years old bone, will no longer fluoresce. And this is very useful because if bones turn out to be more than a hundred years old, then you can be pretty safe in assuming that anyone associated with that event is also going to be dead by this time. You can do some analysis to get some more information, and what we can do is use techniques of elemental analysis to measure the level of specific elements in the bone, and this can enlighten us a little more. This is typically called FUN analysis after three elements fluorine, uranium and nitrogen. Now, fresh bone contains proteins. All proteins contain the element nitrogen, and in fresh bone, if you analyze it, you will find that bone is about 4% nitrogen by weight. However, let's suppose the body is in a grave or somewhere exposed. The proteins in those bones will gradually break down with time, but as the protein molecules break down, the nitrogen containing compounds will diffuse out of the bone into the environment and be lost, which means that the bone nitrogen content will decrease with age. [BLANK_AUDIO] Now, let's turn to the other two elements, fluorine and uranium. These two elements are not naturally present in bone, so the content of these two elements in fresh bone is 0%. There shouldn't be any fluorine or uranium in your bones. Now, suppose those bones are buried in an area where the groundwater contains appreciable amounts of those elements. Okay, they would be leached from the local rocks, then the bones will absorb those elements from the environment, and that means that the concentration of fluorine and uranium will increase with time. Now, you cannot use this as a kind of clock to determine time of death, because the absorption of these elements depends on their presence in the local environment. So if that body is in a place where the local geochemistry means there is no uranium, then of course it will not absorb any uranium however long you leave it. But if it's in an area where there is uranium naturally present as a trace mineral in the rocks, then you will get uranium absorption. So you can't use it as a clock, but you can use it to compare two bones from the same place. And if those two bones have been in the same place for the same length of time, the same number of centuries maybe, then they should have the same amount of uranium and fluorine. Here's an example where this kind of analysis proved critical, and this is the story of Piltdown Man. If we go back about a hundred years or a little bit more, one of the great scientific challenges was finding the ancestors, our own ancestors, the ancestors of homosapiens. Now, the Germans had found the remains of ancient humanoids, and this is Neanderthal Man. The French had found the remains of ancient humanoids as well, and this is Cro-Magnon Man, and since then of course, we also have Peking Man and Java Man, and all the discoveries in East Africa. But 100 years ago, British paleontologists were very disappointed because they had not been able to find any ancient humanoid remains anywhere in Britain. So, they have nothing to compare with the remains found by the Germans and the French. Well, one dig that was going on was at a place called Piltdown, it's a little way outside London, and this was during the period 1912 to 1915. And alongside many, many bones of prehistoric animals, they also found two fragments of humanoid bone, and they claimed that these were approximately 500,000 years old. And so of course, they went to the Natural History Museum in London and they were displayed in Prideaux Place. Now, what they found was two fragments of bone, and you can see the reconstruction in this picture here. What they found is the two dark parts. You can see a skull fragment, and you can see a jaw fragment. And when you look at these fragments, you conclude that the skull fragment is very similar to a modern human whereas the jaw fragment is more similar to a modern ape, which indicates that in evolutionary terms, our brain, our brain cage evolved before our jaw evolved. And this finding was never completely accepted by the community, because the more favoured theory was that the jaw evolved in advance of the brain. Nevertheless, those bone fragments were there in the Natural History Museum until the late 1940s. By the late 1940s, chemical techniques had improved a lot, and someone had the courage to go to these bone fragments and do a little bit of chemical analysis. In fact, he analyzed them for fluorine and nitrogen, and this is what they found. The skull fragment turned out to be 0.2% fluorine, whereas the jaw fragment had essentially no detectable fluorine or almost no fluorine. That means that the two pieces of bone had not been in that site at Piltdown for the same length of time, therefore they could not come from the same individual, they had to come from different individuals. What's more, the jaw fragment turned out to contain almost 4% nitrogen, which meant that the jaw fragment must be essentially a modern piece of bone. Well, it turned out that that jaw fragment actually had been taken from a modern orang-utan, whereas the skull fragment was human, and it was a few centuries old. And it was a hoax - someone had acquired these two bone fragments, had chemically dyed them so that there's the dark colour that you see in the picture and therefore look old, and that person had placed them in the excavation so that they would be found by the paleontologists. Well, it's never been proved who did it. There are suspicions about who might have done it, but of course, after this length of time it's never been proved. The Piltdown Man stands as one of the most famous examples of a scientific fraud, but it's a scientific fraud that's been exposed by chemical analysis. [BLANK_AUDIO]
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