The article points out that footprints in the 3.5 million years old range have been found, these are just the oldest footprints of Stone Age humans.
-- Only two things are infinite, the universe and human
stupidity, and I'm not sure about the former. (Einstein)
Re:Actually ...
by
reverseengineer
·
· Score: 3, Informative
Well, they're footprints of a recent precursor to modern humans, Homo heidelbergensis, which is believed to be the forerunner of both H. neanderthalensis and H. sapiens There are some paleoanthropologists, however, who think that H. heidelbergensis (I just love that name) might only be the direct ancestor of Neanderthals and that the break between H. neanderthalensis and H. sapiens occurred earlier.
It is also interesting to note that these footprints indicate that they were made by beings which were approximately 4.5ft (1.5m) tall, though H. heidelbergensis remains suggest that adults of the species may have been as tall as 6 feet (1.9m). Thus, as the article suggests, these footprints may have been made by children- or they made be from a completely different hominid species.
-- "FDA staff reviewers expressed concern about the number of patients who were left out of the study because they died."
You can tell a lot from the footprints, such as the shape of pelvis bones, relative age and weight of the print maker, frequently the gender of the print-maker... all from the angle of the foot prints. If the prints are the correct proportions for 'human' and have the correct angles for a human walker, then scientists can probably narrow it down to being human prints with great accuracy.
-- The next Slashdot story will be ready soon, but subscribers can beat the rush and slashdot the links early!
You go and pour some fresh concrete or volcano mud, and some idiot goes and writes their initials in it, or steps there. It was the same then as it is now.
Who left the 56 footprints is not clear. But their discoverers suggest either late Homo erectus or Homo heidelbergensis -- two early human species found in Europe during the Paleolithic era, also known as the Stone Age.
When they find the guy that did it, they're going to be MAD!
yo.
Too bad Steve's been debunked
by
Anonymous Coward
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· Score: 2, Informative
Re:How old are they?
by
Anonymous Coward
·
· Score: 2, Insightful
whole rock K-Ar dating on rocks only 10 years old is NEVER going to give you interpretable results.
1) whole rock dating is, as it sounds, dating a rock without regard to the specific mineral phases within it. this is a major point because different minerals have different diffusivities (and therefore closure temperatures) with respect to loss of radiogenic 40Ar.
2) K-Ar dating, while useful, gives results with large uncertainties. for example, a 10 million year old K-Ar date typically has uncertainties on the order of 1-2 million years. with more modern 40Ar/39Ar dating (a variant of K-Ar dating), those uncertanites are more like 0.1 to 0.5 million years.
3) THE SAMPLES ARE ONLY 10 YEARS OLD!!!! that is (by a long shot) not enough time to accumulate radiogenic 40Ar in the sample. the half-life of 40K is just too damn long and given the state of the art in mass spectrometry, there is no way to get a high enough signal to noise (e.g. count enough 40Ar atoms) to calcualate an age (let alone a reliable one). even if you analyze tens of kilograms of sample (which is not practical).
what were the uncertainties of mr. austin's K-Ar dates? geochronologic results without uncertainties are useless.
i hear this crap argument about 10 year old mt. st. helens rocks being dated as hundreds of thousands of years old all the time. it's a load. first (as i discussed above) you can't expect to be able to date a rock that young anyway (at least not with K-Ar, 40Ar/39Ar or any other common isotopic system).
second, this argument takes no account of the geologic context of the samples austin dated. are they indeed volcanic rocks that cooled from a magma 10 years prior to their collection? or were they much older rocks that were blown out of the volcano in the recent eruption. rocks that crystallized from a lava not 10 years prior, but, rather in a much older eruption. say 300 thousand years ago?
>Radiometric dating is not science, since given known-age rocks, the best labs around return wildly wrong results.
you have no clue what you are talking about.
Re:How old are they?
by
fluffy666
·
· Score: 3, Insightful
But given that K-Ar dating is typically used for age ranges in the 10s or 100s of millions of years, these results show that the uncertanty due to primordial argon is small, and hence the method is accurate. Thanks for demonstrating that radiometric dating is reliable.
Re:How old are they?
by
Bowling+Moses
·
· Score: 2, Informative
I took a slightly extended lunch break today and went down to the university library to grab the original paper. There's some truly interesting things about your citing of Dalrymple. First off, you (or whoever your source is--in my experience creationists rarely read the original) didn't read the table right. The numbers that you present are actually the concentration of Ar-40 found in the sample, in 10^-12 mol Ar-40/g sample. The apparent age is in the third column of table 2 on page 51--I won't give them here (you'll have to look it up yourself) but they are much higher than the known age of the rock sample. However in the very first page of the article, Dalrymple states "The use of historic samples for these studies has two important advantages: (1) the ages of the flows are unambiguous, and (2) the material is so young that it is not necessary to make any correction for the 40Ar that is generated by the decay of 40K since the rock formed(emphasis mine)." The point of the study was a check of the methodology for K-Ar dating by looking at original levels of 40Ar present in the sample, not to date the rock sample itself. This is obvious--the half life of K-40 to Ar-40 is ~1.3 billion years so there should be very little Ar-40 in the sample produced by radioactive decay, which is exactly what we find. The most anomolously elevated level of Ar-40 is in the Hualalai sample, with 1.60x10^-12 mol Ar-40/g sample. In table 1 on page 50 we see that that the total amount of Ar-40 in this sample is 115x10^-12 moles, meaning that in this sample there is 1.4% more Ar-40 than is expected. What Dalrymple says about dating young rocks is this: "...anomalous 40Ar/36Ar ratios could be a problem in dating very young rocks. If the present data are representative, argon of slightly anomalous composition can be expected in approximately one out of three volcanic rocks (emphasis mine)." on page 52, meaning that the method would be inappropriate to apply to young samples--thus the USGS' 10,000-year limit (and I imagine the error bars here are still large). However as the rock grows older more Ar-40 will build up as K-40 decays. The more Ar-40 there is, the less that initial anomalous amount of Ar-40 will matter as its percentage of the total Ar-40 present in the rock drops--meaning that (to quote Dalrymple again on pg 52): "...the amounts of excess 40Ar and 36Ar found in the flows with anomalous 40Ar/36Ar ratios were too small to cause serious errors in potassium-argon dating of rocks a few million years old or older." (pg 52) ie. for old samples, the method is perfectly valid.
Slashdot Mirror
This is obviously wrong, the earth is only a little more than 5000 years old.
I've had enough abrasive sigs. Kittens are cute and fuzzy.
The Onion reports the oldest evidence ever found for athlete's foot.
They found a strange building they've called "the worlds oldest Chinese Mann's Theatre", and also in the ground they found the cryptic words:
"Charles Heston"
and two handprints.
Scientists are trying to decode this strange oddity.
~ kjrose
The article points out that footprints in the 3.5 million years old range have been found, these are just the oldest footprints of Stone Age humans.
Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. (Einstein)
see here.
I TOLD them to keep off the lawn...
"Your superior intellect is no match for our puny weapons!"
...the equivalent of the first post!
Who can argue with that?
You can tell a lot from the footprints, such as the shape of pelvis bones, relative age and weight of the print maker, frequently the gender of the print-maker... all from the angle of the foot prints. If the prints are the correct proportions for 'human' and have the correct angles for a human walker, then scientists can probably narrow it down to being human prints with great accuracy.
The next Slashdot story will be ready soon, but subscribers can beat the rush and slashdot the links early!
yo.
Yawn. Look here troll.
whole rock K-Ar dating on rocks only 10 years old is NEVER going to give you interpretable results.
1) whole rock dating is, as it sounds, dating a rock without regard to the specific mineral phases within it. this is a major point because different minerals have different diffusivities (and therefore closure temperatures) with respect to loss of radiogenic 40Ar.
2) K-Ar dating, while useful, gives results with large uncertainties. for example, a 10 million year old K-Ar date typically has uncertainties on the order of 1-2 million years. with more modern 40Ar/39Ar dating (a variant of K-Ar dating), those uncertanites are more like 0.1 to 0.5 million years.
3) THE SAMPLES ARE ONLY 10 YEARS OLD!!!! that is (by a long shot) not enough time to accumulate radiogenic 40Ar in the sample. the half-life of 40K is just too damn long and given the state of the art in mass spectrometry, there is no way to get a high enough signal to noise (e.g. count enough 40Ar atoms) to calcualate an age (let alone a reliable one). even if you analyze tens of kilograms of sample (which is not practical).
what were the uncertainties of mr. austin's K-Ar dates? geochronologic results without uncertainties are useless.
i hear this crap argument about 10 year old mt. st. helens rocks being dated as hundreds of thousands of years old all the time. it's a load. first (as i discussed above) you can't expect to be able to date a rock that young anyway (at least not with K-Ar, 40Ar/39Ar or any other common isotopic system).
second, this argument takes no account of the geologic context of the samples austin dated. are they indeed volcanic rocks that cooled from a magma 10 years prior to their collection? or were they much older rocks that were blown out of the volcano in the recent eruption. rocks that crystallized from a lava not 10 years prior, but, rather in a much older eruption. say 300 thousand years ago?
>Radiometric dating is not science, since given known-age rocks, the best labs around return wildly wrong results.
you have no clue what you are talking about.
But given that K-Ar dating is typically used for age ranges in the 10s or 100s of millions of years, these results show that the uncertanty due to primordial argon is small, and hence the method is accurate. Thanks for demonstrating that radiometric dating is reliable.
I took a slightly extended lunch break today and went down to the university library to grab the original paper. There's some truly interesting things about your citing of Dalrymple. First off, you (or whoever your source is--in my experience creationists rarely read the original) didn't read the table right. The numbers that you present are actually the concentration of Ar-40 found in the sample, in 10^-12 mol Ar-40/g sample. The apparent age is in the third column of table 2 on page 51--I won't give them here (you'll have to look it up yourself) but they are much higher than the known age of the rock sample. However in the very first page of the article, Dalrymple states "The use of historic samples for these studies has two important advantages: (1) the ages of the flows are unambiguous, and (2) the material is so young that it is not necessary to make any correction for the 40Ar that is generated by the decay of 40K since the rock formed(emphasis mine)." The point of the study was a check of the methodology for K-Ar dating by looking at original levels of 40Ar present in the sample, not to date the rock sample itself. This is obvious--the half life of K-40 to Ar-40 is ~1.3 billion years so there should be very little Ar-40 in the sample produced by radioactive decay, which is exactly what we find. The most anomolously elevated level of Ar-40 is in the Hualalai sample, with 1.60x10^-12 mol Ar-40/g sample. In table 1 on page 50 we see that that the total amount of Ar-40 in this sample is 115x10^-12 moles, meaning that in this sample there is 1.4% more Ar-40 than is expected. What Dalrymple says about dating young rocks is this: "...anomalous 40Ar/36Ar ratios could be a problem in dating very young rocks. If the present data are representative, argon of slightly anomalous composition can be expected in approximately one out of three volcanic rocks (emphasis mine)." on page 52, meaning that the method would be inappropriate to apply to young samples--thus the USGS' 10,000-year limit (and I imagine the error bars here are still large). However as the rock grows older more Ar-40 will build up as K-40 decays. The more Ar-40 there is, the less that initial anomalous amount of Ar-40 will matter as its percentage of the total Ar-40 present in the rock drops--meaning that (to quote Dalrymple again on pg 52): "...the amounts of excess 40Ar and 36Ar found in the flows with anomalous 40Ar/36Ar ratios were too small to cause serious errors in potassium-argon dating of rocks a few million years old or older." (pg 52) ie. for old samples, the method is perfectly valid.