The immediate take homeis that our carbon 14 data is vulnerable to natural contaminationable to make the samples far younger than they are. Again this typeof dating is excellent yet vulnerable to unpleasant surprises. Unfortunately we draw conclusions that then inform further researchand get really bitten when it comes to archeology. The first triparound that block was the idea that civilization arose in the middleeast and slowly migrated outward. Correcting ages using 6000 yearsof tree rings turned decades of scholarship on its head. Now we havenicely bumped the Neanderthal to 40,000 years BP or more. I was notbrave enough to say as much on the basis of the time lines that I ampresently working with, but this new dating conforms nicely to myprincipal conjecture.
Effectively the firstconjectured modern human expansion around 45,000 to 40,000 years agocoincides with the plausible subsumation of the Neanderthal linage. It is also reasonable that a number of other human lineages were alsosubsumed. It made little sense that a remnant population wouldremain aloof over thousands of years of interaction with a dominantpopulation.
In the present era, thenative populations of the Americas are been progressively subsumedinto the greater population. It is a slow process that lastscenturies but the results are still the same that takes advantage ofthe reality that people are inclined and generally encouraged tomarry outside their immediate community.
Humanity is wired tocontinuously mix their gene pool and the present elimination ofgeographic isolation has obviously sped that up. The same happened40,000 years ago with populations arising on the continental shelfworld wide.
Neanderthals DiedOut Earlier Than Thought
By Charles Cho
http://ca.news.yahoo.com/neanderthals-died-earlier-thought-193429783.html
These findings hintthat Neanderthals did not coexist with modern humans as long aspreviously suggested, investigators added.
Modern humans onceshared the planet with now-departed human lineages, including theNeanderthals, our closest known extinct relatives. However, there hasbeen heated debate over just how much time and interaction, orinterbreeding, Neanderthals had with modern humans.
To help solve themystery, an international team of researchers investigated 215 bonespreviously excavated from 11 sites in southern Iberia, in an areaknown as Spain today. Neanderthals entered Europe before modernhumans did, and prior research had suggested the last ofthe Neanderthals held out in southern Iberia until about35,000 years ago, potentially sharing the region with modern humansfor thousands of years.
Their data suggestthat modern humans and Neanderthals may have actually lived in thearea at completely different times, never crossing paths there atall. Even so, these findings do not call into question whether modernhumans and Neanderthals once had sex— the findings simply indicatethis interbreeding must have occurred earlier, before modern humansentered Europe.
"The geneticevidence for interbreeding — 1 to 4 percentNeanderthal DNA inpresent-day modern humans — suggests that interbreeding probablyoccurred before the period we are looking at in the Levant, theregion around Israel and Syria, when modern humans first migrated outof Africa," researcher Rachel Wood, an archaeologist andradiocarbon specialist at Australian National University in Canberra,told LiveScience.
Dating bones
Scientists discoverthe ages of artifacts and fossils using a variety of techniques. Forinstance, radiocarbon dating determines the age of biological remainsbased on the ratio between the carbon isotopes (atoms of the sameelement with different numbers of neutrons) carbon-12 and carbon-14it holds — this proportion changes as radioactive carbon-14 breaksdown while stable carbon-12 does not. Researchers can also look atthe layers of soil and rock in which objects are found — if theselayers were not disturbed over the years, then objects in the samelayer should be the same age.
The investigatorsconcentrated on collagen, the part of bone most suited forradiocarbon dating. Only eight of these bones from two sites in Spain— Zafarraya Cave and Jarama VI — had enough collagen foranalysis.
One bone, which camefrom a wild goat, was found in Zafarraya Cave in a similar layer asNeanderthal fossils. The bone was previously estimated as 33,300years in age. However, using an ultrafiltration technique thatcleansed the bone of modern carbon impurities that can giveinaccurate younger dates, they found the bone was more than 46,700years old.
"Our worksuggests that at present, it is unlikely that Neanderthalssurvived any later in this area than they did elsewhere in mainlandEurope," said researcher Thomas Higham at the University ofOxford in England.
The most surprisingthing "was the enormous difference that the ultrafiltrationdating made to the chronologies of the sites we looked at," Woodsaid. "At other sites in Europe, we have seen that this improvedmethod of dating bone makes a difference, making old bones older.However, we do not normally see such consistently large differences.This is probably because the preservation of the organic materials —bone and charcoal — that are normally radiocarbon dated is reallypoor in warm climates like southern Spain."
Analysis of theremaining samples revealed they were at least 10,000 years older thanpreviously estimated. Instead, they were close to or more than 50,000years old, the upper limit for radiocarbon dating.
When Neanderthals diedout
"Our results castdoubt on a hypothesis that has been broadly accepted since the early1990s — that the last place for surviving Neanderthals was in thesouthern Iberian Peninsula," Wood said. "Much of theevidence that has supported this idea is based on a series ofradiocarbon dates, which cluster at around 35,000 years ago. Ourresults call all of these results into question."
These findings suggestmodern humans and Neanderthals might not have interacted in thisarea. In northern Iberia, about 150 miles (250 kilometers) north ofJarama VI, past research suggested modern humans were only presentstarting about 42,000 years ago. These new findings hint that modernhumans and Neanderthals did not coexist for millennia as beforethought, and did not live side-by-side.
"The results ofour study suggest that there are major problems with the dating ofthe last Neanderthals in modern-day Spain," Higham said. "Wenow have to look very cautiously at the model of late Neanderthalsurvival in southern Iberia and focus our efforts on more rigorousdating programs."
One site, Cueva Antónin Spain, did seem as young as previously thought. However, itremains uncertain whether the artifacts there are linked withNeanderthals — they may belong to modern humans.
The researcherscaution they are not definitely saying that there were noNeanderthals in southern Iberia after 42,000 years ago. "What wehave is a gap where we have no reliable radiocarbon dates. Theremight have been Neanderthals or modern humans or both or neither,"Wood said. Also, "there are several circumstances which couldhave obscured later interbreeding events in Europe, so it is notpossible to say, for example, that at one time there was not moreNeanderthal DNA in Europeans."
The scientistsdetailed their findings online Feb. 4 in the journal Proceedings ofthe National Academy of Sciences.
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