Can someone tell me how a skull or bone fragment is analyzed?

[Cindi]

Meaning its age and classification. Such as "Neanderthal" man. They got a few bones but how do they determine the age and genetic composition of the fragment?

[swansont]

Age is typically determined by the rocks in/around which it was found. Typically younger rock is deposited on older rock (exceptions are typically fairly obvious). There are a couple of different methods, depending on the geology. One method: volcanic deposits will contain materials that crystallize as it cools. It can contain Potassium-40, which decays to Argon-40, which is trapped in the crystal. The ratio of the two tells you when the deposit cooled. There are other isotope combinations that can be used, as well.

If the material is geologically young there are some other methods - if it's under ~40-50,000 years and contains terrestrial matter that was once alive, you can do carbon dating (amount of C-14 as compared to the rest of the sample, since the C-14 stops being taken in when the being dies). Some samples found in lake beds can be dated by counting the annual layers of sediment deposited (varves), and you can also count tree rings (dendrochronology)

[Peterkin]

Then comes the fun part of examining the bone itself. Comparison with other remains, size and shape, chemical analysis, sometimes DNA - or at least bits of DNA - can be extracted, growth pattern, rigidity, thickness - all kinds of clues. If you're interested in entry level forensic anthropology, you might check out this BBC program https://www.imdb.com/title/tt11657912/,  runs on all the public tv networks.

[Cindi]

Thanks! My main concern is about sizing up Neanderthal pieces, how they know when this thing lived and how they know they were Neanderthals -- based on what? the DNA? Because some keep talking about how "Neanderthal" DNA is still within certain current humans. Your comments are greatly appreciated.

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[Peterkin]

There is a considerable amount of Neanderthal material available for study - fossils found as far back as the early 19th century. Plenty of information to be gathered. Teeth are usually a good source of ancient DNA, as are intact long bones.

Not only that, there is a lot of associated artefact - tools, weapons, burial pits, etc. which tells us more about how they lived.

Here's a start https://en.wikipedia.org/wiki/List_of_Neanderthal_fossils

[mistermack]

Another point is how they cross check one method with others. If carbon dating from bones agrees with dating from the soil layers, it's not twice as sure, it's more like five times. And if anything's wrong, it will stick out with dates disagreeing with each other. 

Some of the technology in the artefacts can help with dating too. Technology and culture gradually change over time. Just as we can roughly date a car just by looking at the design. 

[CharonY]

4 hours ago, Cindi said:

Thanks! My main concern is about sizing up Neanderthal pieces, how they know when this thing lived and how they know they were Neanderthals -- based on what? the DNA? Because some keep talking about how "Neanderthal" DNA is still within certain current humans. Your comments are greatly appreciated.

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DNA is a fairly new method, falling under the ancient DNA set of techniques and are certainly not the "traditional" way to identify the origins of bones. It is an emerging technique to use on certain bone fragments, as mitochondrial DNA can sometimes be retrieved even from them. But as things go, they are fairly new and not quite standard, I would say.

Traditionally, identification can be done based on bone fragments alone, but requires some level of integrity. Especially highly fragmented bones are difficult to identify, but as long as key morphological pieces can be found, experts can assign them with a high level of accuracy.

 

[Cindi]

7 hours ago, mistermack said:

Another point is how they cross check one method with others. If carbon dating from bones agrees with dating from the soil layers, it's not twice as sure, it's more like five times. And if anything's wrong, it will stick out with dates disagreeing with each other. 

Some of the technology in the artefacts can help with dating too. Technology and culture gradually change over time. Just as we can roughly date a car just by looking at the design. 

OK, I was thinking before I looked on the board again, let's say in the case of "Neanderthal" man. How do they figure the dna composition? (That's one question.) I mean how do they determine it's Neanderthal person and not, let's say, homo sapien? If I'm wrong in my terms, please feel free to correct me.

3 hours ago, CharonY said:

DNA is a fairly new method, falling under the ancient DNA set of techniques and are certainly not the "traditional" way to identify the origins of bones. It is an emerging technique to use on certain bone fragments, as mitochondrial DNA can sometimes be retrieved even from them. But as things go, they are fairly new and not quite standard, I would say.

Traditionally, identification can be done based on bone fragments alone, but requires some level of integrity. Especially highly fragmented bones are difficult to identify, but as long as key morphological pieces can be found, experts can assign them with a high level of accuracy.

 

OK, I appreciate that, but please look at my previous post where I wonder how DNA is analyzed and determined it's from a "Neanderthal" man and not a homo sapien. 

[Peterkin]

1 minute ago, Cindi said:

OK, I was thinking before I looked on the board again, let's say in the case of "Neanderthal" man. How do they figure the dna composition? (That's one question.) I mean how do they determine it's Neanderthal person and not, let's say, homo sapien? If I'm wrong in my terms, please feel free to correct me.

Comparison with samples on file. The name and grouping of a particular Homo subspecies has been reasonably well established, but since there is evidence of interbreeding at many stages of the evolutionary process, and since new finds and methods do still keep intruding, the lines are not drawn in thick black crayon. Matters are complicated by the fact that few specimens yield usable DNA. 

However, the H. neanderthalensis fossil library is quite extensive, so there are lots of partial and intact skulls, teeth, as well as other bones and complete skeletons of different individuals, their group characteristics are quite well documented. So, when one of those bones, or a new one that matches, has enough DNA, the information is added to the database. By now, the genome has been reliably sequenced and available for comparison. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4031459/

[studiot]

17 hours ago, Cindi said:

Meaning its age and classification. Such as "Neanderthal" man. They got a few bones but how do they determine the age and genetic composition of the fragment?

There is almost always more than 'a few bones' of evidence at a site.

Not only that but H. Neanderthalis was abl to think and reason and will have chosen the best locations to live.

Peoples that came later and displaced them will have ovelaid and mixed up with their own material.
This is a double edged sword since on the one hand it damages the archeological record.
But on the other hand it provides comparisons, especially for those things which stand out as 'different'.
Skull shapes and sizes are one such example of a difference that was spotted long ago.

Other records they left include cave paintings of thier world (as they saw it).

8 hours ago, Cindi said:

how they know when this thing lived and how they know they were Neanderthals

And don't you think you are being less than complimentary about your cousins ?

 

[CharonY]

1 hour ago, Cindi said:

OK, I was thinking before I looked on the board again, let's say in the case of "Neanderthal" man. How do they figure the dna composition? (That's one question.) I mean how do they determine it's Neanderthal person and not, let's say, homo sapien? If I'm wrong in my terms, please feel free to correct me.

OK, I appreciate that, but please look at my previous post where I wonder how DNA is analyzed and determined it's from a "Neanderthal" man and not a homo sapien. 

In the case of Neanderthals it was the opposite way, they took samples from bodies that were clearly Neanderthal and isolated first mitochondrial DNA (around 2008 ish?) and later on other groups extracted more DNA from Neanderthal bones. They knew it was Neanderthal DNA because a) they samples were obtained from Neanderthals and b) they cross-referenced it to modern human sequences to make sure that the researchers did not contaminate it with their own DNA.

The sequencing itself is relatively standard compared to other sequencing projects, the really tricky bit is to extract enough workable DNA. Again, this is something you can read up by looking at "ancient DNA" as keywords.

[Cindi]

2 hours ago, CharonY said:

In the case of Neanderthals it was the opposite way, they took samples from bodies that were clearly Neanderthal and isolated first mitochondrial DNA (around 2008 ish?) and later on other groups extracted more DNA from Neanderthal bones. They knew it was Neanderthal DNA because a) they samples were obtained from Neanderthals and b) they cross-referenced it to modern human sequences to make sure that the researchers did not contaminate it with their own DNA.

The sequencing itself is relatively standard compared to other sequencing projects, the really tricky bit is to extract enough workable DNA. Again, this is something you can read up by looking at "ancient DNA" as keywords.

OK, thanks to all. So is it possible that someone here can briefly explain why (really how, not why I guess) Neanderthal dna is different than homo sapien dna?

[Peterkin]

1 hour ago, Cindi said:

OK, thanks to all. So is it possible that someone here can briefly explain why (really how, not why I guess) Neanderthal dna is different than homo sapien dna?

Not without you understanding the structure of DNA, its sequencing and identification of markers.https://en.wikipedia.org/wiki/DNA_sequencing

 

[CharonY]

2 hours ago, Cindi said:

OK, thanks to all. So is it possible that someone here can briefly explain why (really how, not why I guess) Neanderthal dna is different than homo sapien dna?

The DNA is for the most part the same for most organisms (the organization is different between e.g. eukaryotes and prokaryotes, but that is not really relevant when comparing Neanderthals with modern humans). The only difference really is in the sequence. Much of the sequence will be very similar, but the areas where there are differences can be used to figure out relationships.

[mistermack]

19 hours ago, Cindi said:

OK, I was thinking before I looked on the board again, let's say in the case of "Neanderthal" man. How do they figure the dna composition? (That's one question.) I mean how do they determine it's Neanderthal person and not, let's say, homo sapien? If I'm wrong in my terms, please feel free to correct me.

The answer really is "through years of study done by experts in the field". It's not simple enough to explain in a few sentences on a chat forum. If you watch some documentaries on youtube, or read some articles, you will find that there are stand-out features that you can use to identify the remains, and just like dating, cross-checking across features makes identification more certain. For example, the skull of a Neanderthal has some clear differences from Homo Sapiens. Our braincase is more rounded, Neanderthals' are more elongated, like a rugby ball. And Neanderthals have thicker ridges of bone across the eyebrows. Some of it is less obvious, like the relative dimensions of bones. Neanderthals were more stocky, with shorter limbs and stronger bones, in general, compared to us. The differences are small, but unmissable to an expert. And when you have all of the differences in one individual, you can say with a great deal of certainty that it's a Neanderthal, or Homo Sapiens. 

They are even able to say if a Homo Sapiens or Neanderthal is an early or late example, using clues like the ones I've mentioned, even without a positive dating, because we and neanderthals evolved a bit over time. 

So if you make a positive ID of the sample through physical means, and can get a dna sample from the same individual, you can be pretty definite that you have a good dna sample of a neanderthal. 

Having done that, you can look for matching dna in our modern samples, and make a comparison. 

But as I said, you would need to read up, or watch some relevant material, to fully understand how firm identifications are made. 

[Cindi]

6 hours ago, mistermack said:

The answer really is "through years of study done by experts in the field". It's not simple enough to explain in a few sentences on a chat forum. If you watch some documentaries on youtube, or read some articles, you will find that there are stand-out features that you can use to identify the remains, and just like dating, cross-checking across features makes identification more certain. For example, the skull of a Neanderthal has some clear differences from Homo Sapiens. Our braincase is more rounded, Neanderthals' are more elongated, like a rugby ball. And Neanderthals have thicker ridges of bone across the eyebrows. Some of it is less obvious, like the relative dimensions of bones. Neanderthals were more stocky, with shorter limbs and stronger bones, in general, compared to us. The differences are small, but unmissable to an expert. And when you have all of the differences in one individual, you can say with a great deal of certainty that it's a Neanderthal, or Homo Sapiens. 

They are even able to say if a Homo Sapiens or Neanderthal is an early or late example, using clues like the ones I've mentioned, even without a positive dating, because we and neanderthals evolved a bit over time. 

So if you make a positive ID of the sample through physical means, and can get a dna sample from the same individual, you can be pretty definite that you have a good dna sample of a neanderthal. 

Having done that, you can look for matching dna in our modern samples, and make a comparison. 

But as I said, you would need to read up, or watch some relevant material, to fully understand how firm identifications are made. 

On 7/21/2022 at 6:38 PM, CharonY said:

In the case of Neanderthals it was the opposite way, they took samples from bodies that were clearly Neanderthal and isolated first mitochondrial DNA (around 2008 ish?) and later on other groups extracted more DNA from Neanderthal bones. They knew it was Neanderthal DNA because a) they samples were obtained from Neanderthals and b) they cross-referenced it to modern human sequences to make sure that the researchers did not contaminate it with their own DNA.

The sequencing itself is relatively standard compared to other sequencing projects, the really tricky bit is to extract enough workable DNA. Again, this is something you can read up by looking at "ancient DNA" as keywords.

How were these fragments clearly Neanderthal? When I go to the doctor and he prescribes a medication, he usually does not tell me what the side effects are, or what the test results show. And because I sometimes research these things, I sometimes do not take a recommended medication once I read unbiased reports about it. In the case of figuring how scientists decide what type of being a bone fragment is from, if I can't understand the explanation (like dna analysis without outlining it in pretty much detail), I tend to figure, "oh well..." and then think they are just making figures based on some specifics but only they, the ones involved, seem to know what they're doing and then express it is terms the general public will not understand. If I have to become an analyst to find out for myself, that won't happen. Npro time and not enough interest. But who knows? Maybe I'll contact a professor and see what he says. So while I appreciate all the answers here, nothing convinces me that the answers from scientists are beyond doubt.  Thanks though for trying to explain things to me.

[Peterkin]

13 minutes ago, Cindi said:

When I go to the doctor and he prescribes a medication, he usually does not tell me what the side effects are, or what the test results show.

If you ever get the chance again, change doctors.

14 minutes ago, Cindi said:

In the case of figuring how scientists decide what type of being a bone fragment is from, if I can't understand the explanation

I gave you a couple of links that explain it. Several of us have explained various aspect of the identification and classification process.

Oh well....

[J.C.MacSwell]

41 minutes ago, Cindi said:

 So while I appreciate all the answers here, nothing convinces me that the answers from scientists are beyond doubt.  Thanks though for trying to explain things to me.

If you left thinking otherwise, the answers here would have done you a disservice.

Edited July 23, 2022 by J.C.MacSwell

[swansont]

23 hours ago, Cindi said:

How were these fragments clearly Neanderthal?

If they were found along with other parts of a skeleton, possibly with multiple skeletons, it would be pretty obvious. Neanderthal skulls had a distinctive shape with prominent brow ridges, along with other features that differentiated them from H. sapiens.