Human Skull Begins to Fill in 20,000-Year Gap in Fossil Record

By Sophie Bushwick | August 22, 2012 11:15 am

spacing is important

Back in the day, in the northern part of modern-day Laos, an early modern human died and its corpse washed into a nearby cave. Sure, it doesn’t sound like a particularly noteworthy event. But researchers dated the remains of this human’s skull to at least 46,000 years ago, making it the oldest modern human ever discovered in Southeast Asia.

Scientists discovered the skull fragments back in 2009, but have only this week published their findings in the Proceedings of the National Academy of Sciences. Features not found in any earlier specimens of the Homo genus, such as the absence of a brow ridge on the skull’s frontal bone, mark it as a modern human.

The remains had been hidden under layers of sediment that had washed into the cave over the years. Because there were no signs of a dwelling or of a ceremonial burial, the body to which the skull once belonged was probably swept into the cave from outside as well. Luminescence dating, which measures the energy that crystals in the dirt can store, told the researchers that the last time the sediment layer around the skull experienced sunlight or heat—before it drifted into the dark cave—was between 46,000 and 51,000 years ago. And they calculated the skull’s age with uranium-thorium dating, a radiometric technique often used on materials that retain uranium, like bones and teeth. The skull was about 63,000 years old, indicating that it lay outside the cave for a while before it washed in along with the sediment on which it sat.

This time window makes the new fossil at least 20,000 years older than modern human fossils previously uncovered in the same area, illuminating a blank period in the fossil record and providing evidence for the commonly accepted “Out of Africa” theory of human development. How exactly Homo sapiens spread across the globe is still under debate, but according to this hypothesis, modern humans evolved in Africa and then quickly migrated out of the continent. This skull demonstrates that modern humans had reached Southeast Asia by about 60,000 years ago, a migration pattern that aligns with archaeological and genetic evidence, as well as the Out of Africa theory’s predictions.

Image courtesy of Laura Shackelford / University of Illinois at Urbana-Champaign

  • azhure

    im actually starting to doubt if dating techinqiues now a days is really close to a number to what to be expected. there can be a factor a material become old even if its not

  • http://notone Doubting Thomas

    I hate to be a party pooper, but I’ve been seeing a lot of junk science on websites lately, like the one about the new family of spiders that are probably poisonous. Well, duh! All spiders are poisonous, Einstein. Show me one that isn’t, that would be news.
    In this article, the scientists state the skeleton washed into the cave with some dirt about 12000-17000 years after he had died. Doubt it. Not the best explanation. I suppose the scientists leaped to that conclusion because the dirt underneath and above the skeleton both dated to a later date than the skeleton. So what? The skeleton could have been in the cave for a long period of time and then the deluge from a flood or other occurance suspended the skeleton as the dirt deposited. Makes better sense. People loved caves. Living in caves was the going thing. That’s why the famouos cave bear went extinct, in my opinion. We moved in on his turf. Just, sayin’, I believe this guy was in the cave, not somewhere laying on the ground to wash into the cave after 15000 years. Wolves and the like would have gotten the bone and had a field day first. But, hey, believe what you will. I wasn’t there to check your reasoning.

  • nivram

    @ Doubting Thomas – With the few facts you actually have about the state of the body you conclude YOUR story is more likely than the guys who sat in the mud and did the actual work day in and day out for months. Using the same scientific criteria you just applied, I conclude your wife is cheating on you because you are too stupid to keep a woman.

    I love how idiots with no formal training decide what is and what is not “junk science.” You define junk science as – Crap you don’t want to believe. Do you question the science behind your cell phone or television? Atoms don’t actually exist because I have never seen one. Face it, your not qualified to call anything as complicated as a 3rd grade science fair junk science.

  • KateClancy

    As someone very familiar with the scholars on this project and the field site, I can say there was no leaping to any conclusions (well, except what you’re doing, Doubting Thomas). Their methods are pretty non-controversial, their results exciting. Perhaps you could contact the corresponding author of the paper and request a copy so you can have a read. I think you’ll find this research pretty darn awesome.

  • megan130

    DoubtingThoms is the going idiocy that calls itself clever and questioning to justify hewing to old unscientific concepts or just no science but BELIEF. They consider THAT EQUAL to scholarly curiosity and investigation/questioning. Notice how he SLIPPED IN ‘FLOOD’ ie biblical/Mesopotamian lore, which may or may not have environmental historical proof but isn’t during this skull’s era. The Demise of the USA, when better science papers come out of India and China due to poorly US funded or peer allowed shit science here, for ‘fairness to all views’ bs.

  • jojfc

    Really, who still believes humans are only walking around for 6000 years?

    Obviously there have been civilizations before the Egyptians etc etc. However instead of going deeper and deeper into genetics and evolution i would rather see some of the money pour into excavations.

  • RJ

    Since DT has been thoroughly flogged (although in his defense, I suspect his motivations are nothing more than the typical Internet skeptic who MUST vocally debunk everything he reads ), I would like to question Azhure’s response as well.

    I’m no expert in fossil records or dating techniques but I would point out that the article mentions they used more than one technique to base their findings on. That’s enough for me to file this as interesting and very likely trustworthy. If you are an expert in these techniques please enlighten us, or better yet, peer review the published findings.

  • Kono

    The only reason Azhure and Doubting Thomas posted is to generate clicks on their names. Trolling is profit for some.


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