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Author Topic:   Amino Acid Dating
Coyote
Member (Idle past 618 days)
Posts: 6117
Joined: 01-12-2008


Message 5 of 34 (580708)
09-10-2010 7:30 PM


A quick search of Google shows that the majority of articles on the first page of a search for "amino acid racemization" are either old or from creationist sources.

One of the early proponents was Jeff Bada. Bada's early work using racemization on California Indian skeletons was subsequently shown to be in error (e.g., Taylor 1983)*.

I wouldn't trust this technique too much if it is now being pushed by creationists.

* Taylor, R.E., et al., Major Revisions in the Pleistocene Age Assignments for North American Human Skeletons by C-14 Accelerator Mass Spectrometry: None Older Than 11,000 C-14 Years B.P. American Antiquity, Vol. 50, No. 1, 1983, pp. 136-140.

Edited by Coyote, : Format


Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.

Replies to this message:
 Message 9 by faith24, posted 09-10-2010 8:29 PM Coyote has responded

  
Coyote
Member (Idle past 618 days)
Posts: 6117
Joined: 01-12-2008


Message 18 of 34 (580759)
09-10-2010 11:53 PM
Reply to: Message 9 by faith24
09-10-2010 8:29 PM


Amino vs. other dating methods
I heard that there are other method which overlap this one - Amino Acid Racemization? Do you know the relationship between this one and why it must depend on other one, such as C-14?

The two techniques are entirely independent, neither depending on the other.

I do a lot of radiocarbon dating in my work as an archaeologist. Bada tried to get folks interested in amino acid dating going back into the 70s, but the method never really worked as the Taylor article I cited above showed. I don't know any western US archaeologists doing amino acid dating at all any more. We do a lot of radiocarbon dating.

As far as overlap, they do overlap in the time periods they cover, but that is about all.


Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.

This message is a reply to:
 Message 9 by faith24, posted 09-10-2010 8:29 PM faith24 has not yet responded

  
Coyote
Member (Idle past 618 days)
Posts: 6117
Joined: 01-12-2008


Message 19 of 34 (580760)
09-10-2010 11:59 PM
Reply to: Message 15 by faith24
09-10-2010 10:33 PM


AAR errors
Can somebody please basically tell me why Jeff Bada made an error in his methodology for dating California skeletons using Accelerator Mass Spectrometry (AMS) back in 1983? He was the guy that came with a new way of dating fossils - Amino Acid dating. Here is the article:

Bada did not use AMS (a form of radiocarbon dating). He used amino acid racemization. He dated eleven early California skeletons and came up with very old dates.

Others disputed those dates. Finally, Taylor dated those eleven skeletons using AMS dating and established that they were not nearly as old as Bada claimed. These younger ages were more in keeping with the archaeological data.

I am not sure of the exact reasons for the errors in these AAR dates, but most archaeologists don't bother with AAR now, using the radiocarbon method instead, as that has been shown to be reliable.

================

Add: Faith, have I answered your questions?

Edited by Coyote, : No reason given.


Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.

This message is a reply to:
 Message 15 by faith24, posted 09-10-2010 10:33 PM faith24 has responded

Replies to this message:
 Message 20 by faith24, posted 09-11-2010 1:19 AM Coyote has responded

  
Coyote
Member (Idle past 618 days)
Posts: 6117
Joined: 01-12-2008


Message 22 of 34 (580767)
09-11-2010 1:36 AM
Reply to: Message 20 by faith24
09-11-2010 1:19 AM


Re: AAR errors
Right, i see now. Bada's view were incorrect and the errors are rather large up to 50% which is fairly narrow. But in general, i heard that there are better dating methods out there that can confirm this one? Do you happen to know? Thanks!

Confirm which one? AAR is prone to errors and none of the archaeologists I know use it. It has not been confirmed by radiocarbon dating, as the Taylor article I cited above shows. (I have a copy of the article at the office, and have met the author on a number of occasions.)

Radiocarbon dating is used all the time and is able to be both cross-checked and calibrated by comparison to things with annular events, such as tree-rings, glacial varves, some corals, etc. That lets you count directly back into the past, year by year, then radiocarbon date, for example, every tenth tree ring to see how close the radiocarbon dates are to the tree ring (assumed to be accurate to within a year or so). This also lets you calibrate (correct) the radiocarbon dates, as atmospheric fluctuations cause small errors.


Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.

This message is a reply to:
 Message 20 by faith24, posted 09-11-2010 1:19 AM faith24 has responded

Replies to this message:
 Message 23 by faith24, posted 09-11-2010 1:44 AM Coyote has responded

  
Coyote
Member (Idle past 618 days)
Posts: 6117
Joined: 01-12-2008


Message 24 of 34 (580773)
09-11-2010 2:09 AM
Reply to: Message 23 by faith24
09-11-2010 1:44 AM


Re: AAR errors
Well i heard that this method does support other dating methodologies that are sound. If you have many different methods of measuring that work on independent principles, and they all come out to values within error bounds of each other, then this indicator that they are sound methods. Is that true? hrmm...

If a variety of different methods all point to the same answers then that would tend to confirm those answers.

With dating, we have a lot of methods that can be used, and if they all point to the same approximate date that both confirms that date and supports the accuracy of each of the dating methods.

For dating skeletal remains in the past 10,000+ year range, I am not aware that amino acid racemization is very accurate. It certainly is not used by archaeologists that I know, and we want the most accurate dating tools we can find.

You might check the Taylor articles. One is online:

Here

The other is available in American Antiquity, but not online free that I know of. Here is the citation again:

Taylor, R.E., et al., Major Revisions in the Pleistocene Age Assignments for North American Human Skeletons by C-14 Accelerator Mass Spectrometry: None Older Than 11,000 C-14 Years B.P. American Antiquity, Vol. 50, No. 1, 1983, pp. 136-140.

Edited by Coyote, : Format


Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.

This message is a reply to:
 Message 23 by faith24, posted 09-11-2010 1:44 AM faith24 has responded

Replies to this message:
 Message 29 by faith24, posted 09-11-2010 1:00 PM Coyote has responded

  
Coyote
Member (Idle past 618 days)
Posts: 6117
Joined: 01-12-2008


Message 27 of 34 (580800)
09-11-2010 11:27 AM


Here's where Bada went wrong with amino acid dating
I think I have figured out one of the problems with Bada's amino acid dating. The abstract from the Nature article provided some details and reminded me of others. (I have a lot of these original articles at the office, but I haven't dug them out. I even included a Bada article on AAR dating in a publication I edited in the late '70s, along with a rebuttal in a subsequent publication I edited. Haven't looked at those in years!)

Bada calibrated his method using a 1960s radiocarbon date on the Laguna Skull, dating bone collagen. That radiocarbon date was obtained by UCLA (their number UCLA-1233A) and was 17150±1470. A lot of these early bone dates were flawed, as they had not yet determined which materials to extract from bones to get usable dates. This has since been straightened out.

The Laguna skull was radiocarbon dated later using more advanced technology and returned an age less than a third of that figure. That fits with the archaeological context as well.

But this erroneous date that Bada used to calibrate his method threw everything off by a huge amount, and all the early amino acid results he obtained were worthless.

Taylor's AMS dating of many of the skulls that had returned early amino acid dates (some going back 70,000 years) showed that they were generally closer to 5,000 years. That pretty much ended the archaeological use of amino acid dating for west coast bone samples.

Hope this helps.


Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.

  
Coyote
Member (Idle past 618 days)
Posts: 6117
Joined: 01-12-2008


Message 30 of 34 (580816)
09-11-2010 1:26 PM
Reply to: Message 29 by faith24
09-11-2010 1:00 PM


On dating
My experience is with younger dating methods, so that's what I will respond to. RAZD has an excellent thread around here somewhere on age correlations and how all the different methods complement and confirm one another.

1. What are the other methods that can be used to support each other?

This depends on the age. I use radiocarbon dating a lot, and that can be cross-checked with tree-ring dating (and calibration), as well as by dating historical materials of known ages (materials from Egyptian tombs, for example). Those sorts of tests can establish the accuracy of radiocarbon dating beyond any reasonable doubt.

With radiocarbon dating, one important thing an archaeologists should do is learn the tricks and pitfalls. For example, date single pieces of material. If you date a bunch of loose shell or charcoal from different proveniences, you no longer know what your date is telling you. Another thing: get a lot of dates if you can. That way you can establish the age of your site much more accurately. On a recent large project I obtained 31 radiocarbon dates. Another caution: if you date marine organisms you have to correct your dates for upwelling (old carbon sequestered in deep water). That can change your date by several hundred years, but there have been a lot of studies done and we can correct for this error. One way of doing this is dating shell and charcoal from the exact same provenience and comparing the ages.

You can also cross-check radiocarbon dating with any of several other methods, including thermoluminescence, paleomagnetism, etc.

2. How do they support to each other?

See RAZD's thread.

3. What are the assumptions/interpretation being used?

For radiocarbon dating the primary assumption is that the decay constant is a constant rather than a variable.

We do not assume the levels of radiocarbon in the atmosphere, but calibrate against the tree-ring data to correct for atmospheric fluctuations. This lets us eliminate one potential source of error.

We also correct for isotopic fractionation. C14, C13, and C12 are slightly different in weight, and are taken up into the food chain differently. We correct for this to increase the accuracy of the final date.

Here are some good links:

ReligiousTolerance.org Carbon-14 Dating (C-14): Beliefs of New-Earth Creationists

Radiometric Dating: A Christian Perspective by Dr. Roger C. Wiens

This site, BiblicalChronologist.org has a series of good articles on radiocarbon dating.

Tree Ring and C14 Dating

Radiocarbon WEB-info Radiocarbon Laboratory, University of Waikato, New Zealand.

Radiocarbon -- full text of issues, 1959-2003.


Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.

This message is a reply to:
 Message 29 by faith24, posted 09-11-2010 1:00 PM faith24 has responded

Replies to this message:
 Message 31 by faith24, posted 09-11-2010 2:40 PM Coyote has responded

  
Coyote
Member (Idle past 618 days)
Posts: 6117
Joined: 01-12-2008


Message 32 of 34 (580827)
09-11-2010 2:58 PM
Reply to: Message 31 by faith24
09-11-2010 2:40 PM


Re: On dating
Thanks for the help Coyote those are excellent sources, i am reading right now. Just curious, do you accept long or young ages? Those sites you posted looks like their young ages.

There is virtually unanimous agreement that the earth is ca. 4.5 billion years old.

The only folks who dispute this do so for religious, not scientific, reasons.

If I remember, those links also support the ancient age of the earth.

Let me know if you have questions on radiocarbon dating. I am not very knowledgeable on the other radiometric methods, but others here are.


Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.

This message is a reply to:
 Message 31 by faith24, posted 09-11-2010 2:40 PM faith24 has not yet responded

  
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