The enduring puzzle of Hueyatlaco

One of the most frustrating things about science, from the point of view of non-scientists, is that sometimes we have to say "we simply don't know the answer to that yet."

Of course, I'm sure it's frustrating enough to the scientists as well, but at least they should be used to it.  Science is always pushing at the boundaries of what we know, and using evidence and logic to find explanations.  It's inevitable that sometimes even a significant amount of evidence is insufficient to reach a conclusion.  At that point, the only honest thing to say is "we don't know, and may never know."

This drives a lot of people nuts.  The attitude is that because science has proven to be pretty damn good at finding answers, it should have a one hundred percent hit rate.  Meteorologists can't always accurately predict the track or intensity of storms?  Ha, I'd like to have a job where I could be wrong half the time and still get paid!  The promising new cancer drug turns out not to work in vivo?  Don't listen to the medical professionals, they'll say something is good for you today and then say the opposite tomorrow.  This fault is at risk of an imminent earthquake?  Okay, then tell me when, down to the hour and minute, so I can plan ahead.

Otherwise, what good are you scientists, anyhow?

It all comes from a fundamental misapprehension of the scientific process -- that it should provide certainty.  It'd be nice, but the real world usually doesn't cooperate, and sometimes even with their best efforts, the scientists have to admit to being in a situation somewhere between incomplete understanding and complete befuddlement.

I ran into an especially good example of that a couple of days ago because of a dear friend, a history scholar and loyal reader of Skeptophilia, who asked me if I'd ever heard of Hueyatlaco and the Steen-McIntyre report.  She sent me a link from the site Ancient Origins called "Controversy at Hueyatlaco: When Did Humans First Inhabit the Americas?" that (despite a subtle bent toward Ancient Astronauts explanations of things) gives the basics of the story -- and it's a pretty peculiar one, even when you don't credit any of the woo-woo trappings.

Now, keep in mind that until two days ago I'd never heard of this, so I still consider my own knowledge shallow and tentative, and I ask forgiveness for any mistakes or misapprehensions I have (and request a quick note if there's something in this post I can correct).  But this is what I've gathered.

Hueyatlaco is an archaeological dig site in the state of Puebla in central Mexico.  In the 1960s, an archaeologist named Cynthia Irwin-Williams was working at the site and uncovered stone tools and the bones of pre-glacial North American mammals (such as the woolly rhinoceros) that showed signs of having been butchered for meat.  Irwin-Williams thought that such an early site deserved close attention, and she sent samples to the USGS for radioisotope dating.

The results were more than a little perplexing.  The date returned by the USGS was on the order of 250,000 years ago.  This predates modern Homo sapiens by a good fifty thousand years, so -- if the date was accurate -- the tools and the animal bones were associated not with modern humans, but with our predecessors, possibly the Neanderthals or Denisovans (neither of which, for the record, has ever been recorded in the Western Hemisphere).  Also perplexing was that this would push back the earliest hominid occupation of North America not just by a little, but by a factor of sixteen!

It's understandable why the scientists found that hard to swallow.  The idea that humans (or their near relatives) had been in the Americas for 230-odd-thousand years longer than we thought they had, and had left no traces whatsoever during that time except at this one site, was difficult to believe.  So the natural conclusion was reached that the dating of the site was somehow askew.

Then repeated attempts kept giving the same age.

Hueyatlaco [Image licensed under the Creative Commons https://www.flickr.com/photos/xhumpty/, Valsequillo dam, CC BY-SA 2.0]

Most archaeologists stuck to their guns, and said the most parsimonious explanation was still that somehow the dating protocol was being applied incorrectly.  The samples were contaminated with older traces, perhaps, which would give a systematic overestimate for the site's age.  Then, to muddy the waters further, there were allegations of a conspiracy to cover up the anomalous data.  The official report from the USGS simply dropped one of the zeroes, reporting the site's age as 25,000, not 250,000, years.  One of the archaeologists who'd been working on the site, Virginia Steen-McIntyre, was pressured to do her dissertation not on the perplexing Hueyatlaco data, but on more conventional research into volcanic ash strata.  Steen-McIntyre decided, however, that she wouldn't be silenced, and came out with a report of her own, taking apart the critics a point at a time -- and included a claim that she was harassed for being unwilling to stay silent.

Other scientists have tried (and failed) to resolve the odd data.  Biostratigrapher Sam Vanlandingham published two papers, in 2001 and 2004, first reconfirming the dating of the strata not to tens, but hundreds of thousands of years ago, and then (most startling of all) confirming this using microfossils of diatoms from contemporaneous sediments at the site -- and demonstrating that some of those diatom species had been extinct for at least eighty thousand years.

The upshot of it all is that we still don't have an answer.  Most archaeologists still doubt the existence of hominids in the Americas prior to the arrival of the ancestors of the Native Americans on the order of (at the most) twenty thousand years ago, and assert that there is not a single grain of evidence that the Neanderthals and Denisovans (or any other hominids, for that matter) ever made it to the Western Hemisphere.  But that leaves us with a puzzle -- multiple studies, cross-checked and confirmed, keep agreeing with the older date as found by Irwin-Williams, Steen-McIntyre, and others.

So if you've been waiting for an answer... well, that's it, folks.  We don't know.  It's one of the most curious archaeological puzzles I've ever run across, and at this point, the words I hear about it most often from reliable sources are "contentious" and "uncertain" and "controversial."  A lot of experts have a lot of opinions about it, but no one has been able to do any of three things -- explain how the dates could be correct when there's no evidence of hominids in the Americas at any time during the following two hundred thousand years, explain how the dates could be incorrect when they've been independently corroborated multiple times, or demonstrate that the entire thing was some kind of elaborate hoax, along the lines of the Piltdown Man.

As frustrating as it is, that's where we have to leave it if we're going to be scrupulously honest about things.  As good skeptics, we have to be willing to hold the question in abeyance, indefinitely if need be, for want of conclusive evidence to settle it.  In science, the answer "We don't know yet" is always the fallback when the data is insufficient to merit a conclusion -- however that offends our deep desire to be a hundred percent sure about everything in the universe.

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A fight over dates

One of the most frustrating things about science, from the point of view of non-scientists, is that sometimes we have to say "we simply don't know the answer to that yet."

Of course, I'm sure it's frustrating enough to the scientists as well, but at least they should be used to it.  Science is always pushing at the boundaries of what we know, and using evidence and logic to find explanations.  It's inevitable that sometimes even a significant amount of evidence is insufficient to reach a conclusion.  At that point, the only honest thing to say is "we don't know, and may never know."

This drives a lot of people nuts.  The attitude is that because science has proven to be pretty damn good at finding answers, that it should have a 100% hit rate.  Meteorologists can't always accurately predict the track or intensity of storms?  Ha, I'd like to have a job where I could be wrong half the time and still get paid!  The promising new cancer drug turns out not to work in vivo?  Don't listen to the medical professionals, they'll say something is good for you today and then say the opposite tomorrow.  This fault is at risk of an imminent earthquake?  Okay, then tell me when, down to the hour and minute, so I can plan ahead.

Otherwise, what good are you scientists, anyhow?

It all comes from a fundamental misapprehension of the scientific process -- that it should provide certainty.  It'd be nice, but the real world usually doesn't cooperate, and sometimes even with their best efforts, the scientists have to admit befuddlement.

I ran into an especially good example of that a couple of days ago because of a dear friend, a history scholar and loyal reader of Skeptophilia, who asked me if I'd ever heard of Hueyatlaco and the Steen-McIntyre report.  She sent me a link from the rather loopy site s8int called "Details of the Steen-McIntyre Hueyatlaco Coverup" that (despite their seeming bent toward Ancient Astronauts explanations of things) gives the basics of the story -- and it's a pretty peculiar one, even when you don't credit any of the woo-woo trappings.

Now, keep in mind that until two days ago I'd never heard of this, so I still consider my own knowledge shallow and tentative, and I ask forgiveness for any mistakes or misapprehensions I have (and request a quick note if there's something in this post I can correct).  But this is what I've gathered.

Hueyatlaco is an archaeological dig site in the state of Puebla in central Mexico.  In the 1960s, an archaeologist named Cynthia Irwin-Williams was working at the site and uncovered stone tools and the bones of pre-glacial North American mammals (such as the woolly rhinoceros) that showed signs of having been butchered for meat.  Williams thought that such an early site deserved close attention, and she sent samples to the USGS for radioisotope dating.

The results were more than a little perplexing.  The date returned by the USGS was on the order of 250,000 years ago.  This predates modern Homo sapiens by a good fifty thousand years, so -- if the date was accurate -- the tools and the animal bones were associated not with modern humans, but with our predecessors, possibly the Neanderthals or Denisovans.  Also perplexing was that this would push back the earliest hominid occupation of North America not just by a little, but by a factor of sixteen!

It's understandable why the scientists found that hard to swallow.  The idea that humans (or their near relatives) had been in the Americas for 230-odd-thousand years longer than we thought they had, and had left no traces whatsoever during that time except at this one site, was difficult to believe.  So the natural conclusion was reached that the dating of the site was somehow askew.

Then repeated attempts kept giving the same age.

Hueyatlaco [Image licensed under the Creative Commons https://www.flickr.com/photos/xhumpty/, Valsequillo dam, CC BY-SA 2.0]

Most archaeologists stuck to their guns, and said the most parsimonious explanation was still that somehow the dating protocol was being applied incorrectly.  The samples were contaminated with older rocks, perhaps, which would give a systematic overestimate for the site's age.  Then, to muddy the waters further, there were allegations of a conspiracy to cover up the anomalous data.  The official report from the USGS simply dropped one of the zeroes, reporting the site's age as 25,000, not 250,000 years.  One of the archaeologists who'd been working on the site, Virginia Steen-McIntyre, was pressured to do her dissertation not on the perplexing Hueyatlaco data, but on more conventional research into volcanic ash strata.  Steen-McIntyre decided, however, that she wouldn't be silenced, and came out with a report of her own, taking apart the critics a point at a time -- and included a claim that she was harassed for being unwilling to stay silent.

Other scientists have tried (and failed) to resolve the odd data.  Biostratigrapher Sam Vanlandingham published two papers, in 2001 and 2004, first reconfirming the dating of the strata to not tens, but hundreds of thousands of years ago, and then (most startling of all) confirming this using microfossils of diatoms from contemporaneous sediments at the site -- and demonstrating that those diatom species had been extinct for at least eighty thousand years.

The upshot of it all is that we still don't have an answer.  Most archaeologists still doubt the existence of hominids in the Americas prior to the arrival of the ancestors of the Native Americans on the order of (at the most) twenty thousand years ago, and assert that there is not a single grain of evidence that the Neanderthals and Denisovans (or any other hominds, for that matter) ever made it to the Western Hemisphere.  But that leaves us with a puzzle -- multiple studies, cross-checked and confirmed, keep agreeing with the older date as found by Irwin-Williams, Steen-McIntyre, and others.

So if you've been waiting for an answer... well, that's it, folks.  We don't know.  It's one of the most curious archaeological puzzles I've ever run across, and at this point, the words I hear about it most often from reliable sources are "contentious" and "uncertain" and "controversial."  A lot of experts have a lot of opinions about it, but no one has been able to do either of two things -- explain how the dates could be correct when there's no evidence of hominids in the Americas at any time during the next two hundred thousand years, or explain how the dates could be incorrect when they've been independently corroborated multiple times.

As frustrating as it is, that's where we have to leave it if we're going to be scrupulously honest about things.  As good skeptics, we have to be willing to leave the question in abeyance, indefinitely if need be, for want of conclusive evidence to settle it.  In science, the answer "We don't know yet" is always the fallback when the data is insufficient to merit a conclusion -- however that offends our deep desire to be a hundred percent sure about everything in the universe.

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This week's Skeptophilia book of the week is brand new; Brian Clegg's wonderful Dark Matter and Dark Energy: The Hidden 95% of the Universe.  In this book, Clegg outlines "the biggest puzzle science has ever faced" -- the evidence for the substances that provide the majority of the gravitational force holding the nearby universe together, while simultaneously making the universe as a whole fly apart -- and which has (thus far) completely resisted all attempts to ascertain its nature.

Clegg also gives us some of the cutting-edge explanations physicists are now proposing, and the experiments that are being done to test them.  The science is sure to change quickly -- every week we seem to hear about new data providing information on the dark 95% of what's around us -- but if you want the most recently-crafted lens on the subject, this is it.

[Note: if you purchase this book from the image/link below, part of the proceeds goes to support Skeptophilia!]

The error of their ways

I recently started teaching the unit on evolution in my introductory biology class, and that always gets me thinking.  The conflict between evolutionary (i.e. scientific) views of the universe and young-earth creationist (i.e. unscientific) models can cause a great deal of stress in students' minds.  Children of evangelical parents are often put in the intensely uncomfortable position of either having to contradict a teacher they may like and respect, or else betray the ideals by which they were raised (and in that view, perhaps jeopardizing their standing with god in the process).

Of course, it's not the only subject I teach that is controversial.  Climate change is at least as hackles-raising as evolution is, these days, and there is a small but highly vocal minority in our community that bristles at any mention of the value of vaccination.  And therein lies the problem; to what extent is it incumbent upon a science teacher to be straightforward about his/her stance with regards to controversial topics about which the scientific world is at consensus?

It's different for teachers of politics and government.  There, the fairest of us strive to keep our own views out of things, because (in the words of a former principal I worked for) we need to remember that children are a captive audience, and the line between teaching and proselytizing can be crossed awfully easily.  I have no difficulty keeping my opinions to myself when I teach the ethics unit in my Critical Thinking class; my stock line is that my views on the questions we discuss are irrelevant.  It is my job instead to needle everyone, and get all the students to consider their stances in a thoughtful manner regardless of whether or not they resemble my own.  "If you are really that interested in what I think," I tell them, "I'll answer any question you like... after you graduate."

The situation is different in science.  Science is, at its basis, not about opinions, it's about facts and inferences.  When an anti-vaxxer says that the MMR shot is linked to autism, (s)he is making a statement that either lines up with the available evidence, or else not.  And in this case, it clearly does not.  So to what extent should I respect a student's right to persist in an erroneous belief out of a desire to keep the peace, and to abide by my long-ago principal's dictum to keep in mind that we are not supposed to proselytize?

As I've grown older, I've become less and less cautious about this -- due, in part, to a feeling of "I've done this job long enough to know what I'm doing," and in part to a sense that to allow false beliefs to go unchallenged is exactly the opposite of what a science teacher should be doing.  I have no doubt that if our chemistry teacher was faced with a student who thought that atoms were made of tiny balls of cream cheese, she would not hesitate to say, "I'm sorry, but you're wrong."  Why are we so afraid to do this in the case of evolution, climate change, and the efficacy of vaccination?

The answer, of course, lies in the deep emotional charge that these topics carry.  There's a feeling that by so doing, we've crossed the line into dictating a student's politics and religion.  And while I do my best to keep my political beliefs to myself -- I steadfastly refuse to get into political discussions with students -- I'm well known in my school and community as being an atheist, and the last thing I want is to be seen as having some kind of axe to grind apropos of tearing down some poor kid's dearly-held religious beliefs.

But still.  The statement "the Earth is 6,000 years old" is simply factually incorrect.  So is "the Earth's climate is not warming up."  Is my reluctance to come out and say that to my students, to leave those erroneous beliefs unchallenged, effectively allowing them to remain willfully ignorant?

[image courtesy of the Wikimedia Commons]

Well, yes.  Yes, it is.  There are probably kinder and gentler ways to say it, but in these cases, "I'm sorry, you're wrong," is a literal statement of fact.  We're not doing kids any favors by pretending along with them that they can hold a counterfactual worldview without being challenged.  It does put them in a bind, though; most of the kids I've known who were young-earth creationists, climate change deniers, and anti-vaxxers have learned those beliefs from their parents.  But consider: if these kids can't be steered in the right direction by science teachers -- on topics where scientists have come to near 100% agreement -- haven't we failed to do the job we have been entrusted with?

It is not our responsibility to convince those children who won't be convinced, just as it is not our responsibility to ensure that every child studies and does his/her assignments.  That same principal I mentioned earlier also used to say, "Every kid has the right to fail."  It applies just as well here.  Faced with facts, logic, and rational argument, kids are perfectly within their rights to reject them.  But science teachers have to be brave enough to present those facts, logic and arguments, and weather the backlash that might result.  What I say to my Critical Thinking students could well apply to every student entering every science class we teach: "You may leave this class with your ideas unchanged.  You may not leave this class with your ideas unchallenged.  After that, it's up to you."