A terrestrial heartbeat

When I was an undergraduate at the University of Louisiana, I took a class called Introduction to Astronomy from a fellow named Daniel Whitmire.  Dr. Whitmire made a name for himself, along with a colleague named John Matese (whom I later took a class in Quantum Mechanics from), with something that's been nicknamed the "Planet X" hypothesis.  This isn't some crazy, Nibiru-is-headed-toward-Earth claim; Whitmire and Matese were looking at an apparent periodicity in mass extinctions, which they suggested could be the effects of a massive planet far beyond the orbit of Pluto, perhaps with an eccentric orbit, which every so often passes through a dense part of the Oort Cloud and sends comets and other debris hurtling in toward the inner Solar System.

Since the time I first heard about it (in around 1980), the Planet X hypothesis has lost currency.  There's been no evidence whatsoever of a massive planet outside the orbit of Pluto, and in any case, further study has indicated that the extinctions (1) don't really show that strong a periodicity, and (2) have been pretty well explained from phenomena other than collisions (other than, obviously, the Cretaceous-Tertiary extinction).

[Image is in the Public Domain courtesy of NASA]

I found out last week, though, that Whitmire and Matese may have been on to something after all.

A curious paper that recently appeared in Geoscience Frontiers suggests that focusing solely on the extinctions may have hidden an underlying periodicity.  In "A Pulse of the Earth: A 27.5-Myr [million year] underlying cycle in coordinated geological events over the last 260 Myr," Michael Rampino and Yuhong Zhu (of New York University) and Ken Caldeira (of the Carnegie Institution for Science) did some detailed statistical analysis (the mathematics of which is beyond me) on 89 different major geological events on Earth -- marine and non-marine extinctions, major ocean-anoxic events, continental flood-basalt eruptions, sea-level fluctuations, global pulses of intraplate magmatism -- and found that there are striking, 27.5 million year peaks that have yet to be explained.

What jumped out at me is that the analysis isn't just some vague, it-looks-like-it-might-be-a-pattern.  The software they used found that the periodicity has a 96% confidence -- i.e. there's only a 4% chance that it's just noise that happens to look like a rhythm.  This means that they're on to something.  What, exactly, they're on to remains to be seen; the natural inclination is to look for some kind of tectonic process that for some reason is on a really slow cycle, but they did note one other curious possibility:

On the other hand, the main period of about 30 Myr is close to the Solar System’s ~ 32 ± 3 Myr vertical oscillation about the mid-plane of the Galaxy.  In the Galactic plane region, increased cosmic-ray flux might lead to significant climatic changes, whereas encounters with concentrations of disk-dark matter might trigger comet showers from the Oort Cloud, as well as thermal and geophysical disturbances in the inner Earth.  We note that a 26 to 37 Myr cycle has been reported in the ages of terrestrial impact craters, using various statistical techniques and sets of crater ages potentially connecting the terrestrial and extraterrestrial cycles.

Of course, figuring out the mechanism that causes the pattern comes after establishing that the pattern itself is real.  As I pointed out in my post on the Ganzfeld Experiment a couple of weeks ago, developing a model to explain a phenomenon has to wait until you've shown that there's a phenomenon there to explain.

But a 96% confidence level is enough to indicate that there's some underlying mechanism at work here that's worth further study.  Something, apparently, is causing a strange, regular pulse of catastrophes.  (To put your minds at ease -- I know this was one of the first things I wondered -- the last peak the analysis found occurred 12.1 million years ago, so we've got another fifteen-odd million years to go before the next one.  That is, if we don't manufacture a cataclysm ourselves first.)

For now, all we have is an odd, unexplained pattern in geological upheavals.  It will be fascinating to see what refinements are put on the analysis -- and whether the scientists can find out what's actually going on.  Until then, we're left with a mystery -- a 27.5 million year terrestrial heartbeat.

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Effect-before-cause

Astrophysicist Neil deGrasse Tyson said (apropos of UFO sightings), "The human brain and perceptual systems are rife with ways of getting it wrong."

It might be humbling, but it's nothing short of the plain truth, and doesn't just apply to seeing alien spaceships.  Especially in perfectly ordinary situations, we like to think that what we're hearing and seeing is an accurate reflection of what's actually out there, but the fact is we not only miss entirely a significant fraction of what we're experiencing, we misinterpret a good chunk of the rest.

Think you're immune?  Watch the following two-minute video, and see if you can figure out who killed Lord Smythe.

I don't know about you, but I didn't do so well.

It turns out that we don't just miss things that are there, we sometimes see things that aren't there.  Take, for example, the research that appeared last week in the journal Psychological Science, that suggests we make guesses about what we're going to see, and if those guesses don't line up with what actually happens, we "see" what we thought we were going to see rather than reality.

The experiment was simple enough.  It uses a short video of three squares (call them A, B, and C, from left to right).  Square A starts to move quickly to the right, and "collides" with B, which starts to move.  As you track it across the screen, it looks like B is going to collide with C, and repeat what happened in the previous collision.

The problem is, square C starts to move not only before B hits it, but before B itself starts moving.  In other words, there is no way a collision with B could have been what triggered C to start moving.  But when test subjects were asked what order the squares started moving, just about everyone said A, then B, then C.  Our expectation of cause-and-effect are so strong that even on multiple viewings, test subjects still didn't see C begin to move before B.

"We have a strong assumption that we know, through direct perception, the order in which events happen around us," said study co-author Christos Bechlivanidis, of University College London.  "The order of events in the world is the order of our perceptions.  The visual signal of the glass shattering follows the signal of the glass hitting the ground, and that is taken as irrefutable evidence that this is indeed how the events occurred.  Our research points to the opposite direction, namely, that it is causal perceptions or expectations that tell us in what order things happen.  If I believe that the impact is necessary for the glass to break, I perceive the shattering after the impact, even if due to some crazy coincidence, the events followed a different order.  In other words, it appears that, especially in short timescales, it is causation that tells us the time."

As I and many others have pointed out about previous research into what is now known as "inattentional blindness," this is yet another nail in the coffin of eyewitness testimony as the gold standard of evidence in the court of law.  We still rely on "I saw it with my own eyes!" as the touchstone for the truth, even though experiment after experiment has shown how unreliable our sensory-perceptive systems are.  Add to that how plastic our memories are, and it's a travesty that people's fates are decided by juries based upon eyewitness accounts of what happened, sometimes in the distant past.

[Image licensed under the Creative Commons Eric Chan from Palo Alto, United States, Mock trial closing, CC BY 2.0]

To end with another quote by NdGT -- "There's no such thing as good eyewitness testimony and bad eyewitness testimony.  It's all bad."

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Siding with the tribe

Springboarding off yesterday's post, about our unfortunate tendency to believe false claims if we hear them repeated often enough, today we have another kind of discouraging bit of psychological research; our behavior is strongly influenced by group membership -- even if we know from the start that the group we're in is arbitrary, randomly chosen, and entirely meaningless.

Psychologists Marcel Montrey and Thomas Shultz of McGill University set up a fascinating experiment in which volunteers were assigned at random to one of two groups, then instructed to play a simple computer game called "Where's the Rabbit?" in which a simulated rabbit is choosing between two different nest sites.  The participant gets five points if (s)he correctly guesses where the rabbit is going.  In each subsequent round, the rabbit has a 90% chance of picking the same nest again, and a 10% chance of switching to the other.

The twist comes when in mid-game, the participants are offered the option of seeing the guesses of three members from either group (or a mix of the two).  They can also pay two points to use a "rabbit-finding machine" which is set up to be unreliable -- it has a two-thirds chance of getting it right, and a one-third chance of getting it wrong (and the participants know this).  Given that this is (1) expensive, points-wise, and (2) already a lower likelihood of success than simply working on your own and basing your guess on what the rabbit did in the previous round, you'd think no one would choose this option, right?

Wrong.  It turns out that when you looked at how people chose, they were way more likely to do the same thing as the people who belonged to their own group.  Next in likelihood is the wonky, inaccurate rabbit-finding machine.  Dead last was copying what was done by members of the other group.

[Image licensed under the Creative Commons Sara 506, Group people icon, CC BY-SA 3.0]

Remember what I started with -- these groups were entirely arbitrary.  Group affiliation was assigned at the beginning of the experiment by the researchers, and had nothing to do with the participants' intelligence, or even with their previous success at the game.  But the volunteers were still more likely to side with the members of their own tribe.  In fact, when choosing whose decisions to observe, the test subjects decided by a two-to-one margin to consult in-group members and not even consider the decisions made by the out-group.

How much more powerful would this effect be if the group membership wasn't arbitrary, but involved an identity that we're deeply invested in?

"Researchers have known for some time that people prefer to copy members of their own social group (e.g., political affiliation, race, religion, etc.), but have often assumed that this is because group members are more familiar with or similar to each other," said study co-author Marcel Montrey, in an interview in PsyPost.  "However, our research suggests that people are more likely to copy members of their own group even when they have nothing in common.  Simply belonging to the same random group seems to be enough.  Surprisingly, we found that even people who rated their own group as less competent still preferred to copy its members."

It's easy to see how this tendency can be exploited by advertisers and politicians.  "Human social learning is a complex and multifaceted phenomenon, where many factors other than group membership play a role," Montrey said.  "For example, we know that people also prefer to copy successful, popular, or prestigious individuals, which is why companies advertise through endorsements.  How do people’s various learning biases interact, and which ones are most important?  Because these questions have only recently begun to be explored, the real-world relevance of our findings is still up in the air."

This also undoubtedly plays a role in the echo-chamber effect, about which I've written here more than once -- and which is routinely amplified by social media platforms.  "By offering such fine-grained control over whom users observe," Montrey said, "these platforms may spur the creation of homogeneous social networks, in which individuals are more inclined to copy others because they belong to the same social group."

We like to think of ourselves as modern and knowledgeable and savvy, but the truth is that we still retain a core of tribalism that it's awfully hard to overcome.  Consider how often you hear people say things like, "I'll only vote for a person if they belong to the _____ Party."  I've sometimes asked, in some bewilderment, "Even if the person in question is known to be dishonest and corrupt, and their opponent isn't?"  Appallingly, the response is often, "Yes.  I just don't trust people of the other party."

And of course, a great many of the politicians themselves encourage this kind of thinking.  If you can get a voter to eliminate out of hand half of the candidates for no other reason than party affiliation, it raises the likelihood you'll be the one who gets elected.  So the benefits are obvious.

Unfortunately, once you look at the Montrey and Shultz study, the downsides of this sort of thinking should also be frighteningly obvious.

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Truth by repetition

You probably have heard the quote attributed to Nazi propaganda minister Joseph Goebbels: "If you tell a lie big enough and continue to repeat it, eventually people will come to believe it."  This has become a staple tactic in political rhetoric -- an obvious recent example being Donald Trump's oft-repeated declaration that he won the 2020 presidential election, despite bipartisan analysis across the United States demonstrating unequivocally that this is false.  (The tactic works; a huge number of Trump supporters still think the election was stolen.)

It turns out that the "illusory truth effect" or "truth-by-repetition effect," as the phenomenon is called, still works even if the claim is entirely implausible.  A study by psychologist Doris Lacassagne at the Université Catholique de Louvain (in Belgium) recently presented 232 test subjects with a variety of ridiculous statements, including "the Earth is a perfect cube," "smoking is good for the lungs," "elephants weigh less than ants," and "rugby is the sport associated with Wimbledon."  In the first phase of the experiment, they were asked to rate the statements not for plausibility, but for how "interesting" they were.  After this, the volunteers were given lists of statements to evaluate for plausibility, and were told ahead of time that some of the statements would be repeated, and that there would be statements from the first list included on the second along with completely new claims.

The results were a little alarming, and support Goebbels's approach to lying.  The false statements -- even some of the entirely ridiculous ones -- gained plausibility from repetition.  (To be fair, the ratings still had average scores on the "false" side of the rating spectrum; but they did shift toward increasing veracity.)

The ones that showed the greatest shift were the ones that required at least a vague familiarity with science or technical matters, such as "monsoons are caused by earthquakes."  It only took a few repetitions to generate movement toward the "true" end of the rating scale, which is scary.  Not all the news was bad, though; although 53% of the participants showed a positive illusory truth effect, 28% showed a negative effect -- repeating false statements triggered their plausibility assessments to decrease.  (I wonder if this was because people who actually know what they're talking about become increasingly pissed off by seeing the same idiotic statement over and over.  I suspect that's how I would react.)

Of course, recognizing that statements are false requires some background knowledge.  I'd be much more likely to fall for believing a false statement about (for example) economics, because I don't know much about the subject; presumably I'd be much harder to fool about biology.  It's very easy for us to see some claim about a subject we're not that familiar with and say, "Huh!  I didn't know that!" rather than checking its veracity -- especially if we see the same claim made over and over.

[Image licensed under the Creative Commons Zabou, Politics, CC BY 3.0]

I honestly have no idea what we could do about this.  The downside of the Freedom of Speech amendment in the Constitution of the United States means that with a limited number of exceptions -- slander, threats of violence, vulgarity, and hate speech come to mind -- people can pretty much say what they want on television.  The revocation of the FCC's Fairness Doctrine in 1987 meant that news media no longer were required to give a balanced presentation of all sides of the issues, and set us up for the morass of partisan editorializing that the nightly news has become in the last few years.  (And, as I've pointed out more than once, it's not just outright lying that is the problem; partisan media does as much damage by what they don't tell you as what they do.  If a particular news channel's favorite political figure does something godawful, and the powers-that-be at the channel simply decide not to mention it, the listeners will never find out about  it -- especially given that another very successful media tactic has been convincing the consumers that "everyone is lying to you except us.")

It's a quandary.  There's currently no way to compel news commentators to tell the truth, or to force them to tell their listeners parts of the news that won't sit well with them.  Unless what the commentator says causes demonstrable harm, the FCC pretty much has its hands tied.

So the Lacassagne study seems to suggest that as bad as partisan lies have gotten, we haven't nearly reached the bottom of the barrel yet.

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Sense, nonsense, and microwaves

One of the difficulties in detecting spurious claims occurs when the writer (or speaker) mixes fact, and real science, in with spurious bits and stirs the resulting hash so thoroughly that it's hard to tell which is which.  When a claim is made of unadulterated bullshit, our job is easier.  Mixtures of science and pseudoscience, though, are often hard to tease apart.

A loyal reader of Skeptophilia sent me a good example of this yesterday, a link to an article on the website NaturalSociety called "Microwave Dangers - Why You Should Not Use A Microwave."  

[Image licensed under the Creative Commons Mk2010, Microwave oven (interior), CC BY-SA 3.0]

In this piece, author Mike Barrett describes the terrible things that microwave ovens do to the people who use them and to the food that's cooked in them.  Amongst the claims Barrett makes:

1. Microwave ovens heat food by making water molecules move "at an incredible speed."  This differs from conventional ovens, which gradually transfer heat into the food "by convection."  Further, this energy transfer into the water molecules results in their being "torn apart and vigorously deformed."
2. Microwaves are radiation.  This radiation can "cause physical alterations" even though microwaves are classified as "non-ionizing."  This radiation "accumulates over time and never goes away."
3. Microwave exposure has a greater effect on your brain than on your other body parts, because "microwave frequencies are very similar to the frequencies of your brain," and this causes "resonance."
4. Exposure to microwaves causes all sorts of problems, from cancer to cataracts and everything in between.
5. Raw foods have "life energy" in the form of "biophotons," that came directly from the sun.  These "biophotons" contain "bio-information," which is why eating sun-ripened raw fruits makes you feel happy.  Microwaving food destroys the "biophotons" which makes it lose all of its nutritional value.
6. Microwaving foods causes the conversion of many organic molecules into carcinogens.
7. Microwave ovens were invented by the Nazis.

Okay, let's look at these claims one at a time.

1. First, all heating of food makes the molecules move faster.  That's what an increase in temperature means.  A piece of broccoli heated to 60 C in a microwave and a piece of broccoli heated to 60 C in a steamer have equal average molecular speeds.  Ordinary ovens don't heat most foods by convection; convection heating requires bits of the food itself to move -- so, for example, heating a pot of soup on the stove creates convection, where the bottom part of the soup, in contact with the base of the pot, gets heated first, then rises, carrying its heat energy with it.  Foods in conventional ovens are heated by a combination of radiation from the heating coils, and conduction of that heat energy into the food from the outside in.  Further, heating the water molecules doesn't "tear them apart," because then you'd have hydrogen and oxygen gas, not water.
2. Microwaves are radiation.  So is sunlight.  Sure, microwaves can cause physical alterations, which is why it's inadvisable to climb inside a microwave oven and turn it on.  But not all kinds of radiation accumulate; the microwaves themselves are gone within a millisecond (absorbed and converted into heat) of when the magneto shuts off, otherwise it wouldn't be safe to open the door.  Barrett seems to be making an unfortunately common error, which is to confuse radiation with radioactivity.  Radioactive substances, or at least some of them, do bioaccumulate, which is why strontium-90 showed up in cows' milk following the Chernobyl disaster.  But your microwaved bowl of clam chowder is not radioactive, it's just hot.
3. When oscillations of one body trigger oscillations of another body at the same frequency, this is called resonance.  However, your brain does not oscillate at the frequency as microwaves -- the frequency he quotes for microwaves inside a microwave oven is 2,450 megahertz (2.45 billion times per second), which is actually correct.  Brains, on the other hand, don't oscillate at all, unless you happen to be at a Metallica concert.
4. Agreed, exposure to microwaves isn't good for you.   Thus my suggestion in (2) above not to get inside a microwave oven and turn it on.
5. There is no such thing as a "biophoton."  You do not absorb useful energy in the form of photons in any case, for the very good reason that you are not a plant.  The only "bio-information" we have is our DNA.  Sun-ripened fruit may taste better, as it's ripened more slowly and has a longer time to develop sugars and esters (the compounds that give fruits their characteristic smell and taste), but microwaves don't destroy "life energy."  This bit is complete nonsense.
6. Microwaving food may cause some small-scale alterations of organic molecules into carcinogens, but so does all cooking.  In fact, the prize for the highest introduction of carcinogens into food has to be awarded to grilling -- the blackened bits on a charcoal-grilled t-bone steak contain polycyclic aromatic hydrocarbons, which are known carcinogens.  The problem is, they're also very tasty carcinogens, which is why I still like grilled steaks.
7. Microwave ovens weren't invented by the Nazis.  The first microwave oven was built by Percy Spencer, an engineer from Maine, in 1945.  The mention of the Nazis seemed only to be thrown in there to give the argument a nice sauce of evil ("anything the Nazis invented must be bad").  But it's false in any case, so there you are.

So, anyhow, that's my analysis of Barrett's anti-microwave screed.  He's pretty canny, the way he scatters in actual facts and correct science with poorly-understood science, pseudoscience, and outright nonsense; the difficulty is, you have to have a pretty good background in science to tell which is which.  All of which argues for better science education, and better education in critical thinking skills.  But any effort I make in that direction will have to wait, because my coffee's getting cold, and I need to go nuke it for a couple of seconds.

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King of the whales

For a long time, one of the biggest evolutionary mysteries was the evolution of whales and dolphins.

Even for someone steeped in the evolutionary model, it was hard to imagine how these aquatic creatures descended from terrestrial mammals.  That they did was undeniable; not only do some species have vestigial hip and hind leg bones, inside their flippers they have exactly the same number and arrangement of arm bones as you have -- one humerus, radius, and ulna; seven carpals; five metacarpals; and fourteen phalanges.  If whales were a "special creation," it's hard to imagine why a Creator would have given them 29 articulated arm bones and then completely encased them in a flat, muscular flipper.

Skeleton of a baleen whale (drawing from the Meyers Konversationslexikon (1888) [Image is in the Public Domain]

So their relationship to terrestrial mammals was obvious, but what wasn't obvious is how they got to where they are today.

Then in 1981 a fossil bed was uncovered in the Kuldana Formation of Pakistan, a sedimentary deposit from what was a shallow marine estuary back in the early Eocene Epoch (on the order of fifty million years ago), that contained a treasure trove of fossilized cetaceans.  This allowed researchers to piece together the evolution of whales and dolphins, placing them in Order Artiodactyla (their closest terrestrial relatives appear to be hippos).  

Skeleton of Ambulocetus, one of the amphibious species of cetaceans linking their terrestrial ancestors with today's aquatic whales [Image licensed under the Creative Commons Notafly, AmbulocetusNatansPisa, CC BY-SA 3.0]

Back in the Eocene, some of these proto-cetaceans were some badass apex predators.  Take Basilosaurus -- the name is Greek for "king lizard," a misnomer, at least the "lizard" part -- which lived in the Tethys Ocean, a body of water that has since been largely erased by plate tectonics.  (The Mediterranean, Black, and Caspian Seas are about all that's left of it.)  Basilosaurus could get to twenty meters in length, and probably ate large fish like sharks and tuna.  It's Basilosaurus that got me to thinking about this topic in the first place; a couple of loyal readers of Skeptophilia sent me a link to an article about a new fossil discovery in Peru.  It's hard to imagine it, but the now bone-dry Ocucaje Desert of southern Peru was once the floor of a shallow sea, an embayment of the (at that point) rapidly shrinking Tethys.  It's provided huge numbers of Eocene fossils, but the one they just found is pretty spectacular; a complete, well-preserved skull of a Basilosaurus that when it was alive was on the order of seventeen meters from tip to tail.

"This is an extraordinary find because of its great state of preservation," said Rodolfo Salas-Gismondi, part of the team that found the fossil.  "This animal was one of the largest predators of its time.  At that time the Peruvian sea was warm.  Thanks to this type of fossil, we can reconstruct the history of the Peruvian sea."

It's fascinating that we're still piecing together the evolution, ecology, and geology of the ancient world -- in this case, a world with carnivorous proto-whales twice as long as a school bus, equipped with big nasty pointy teeth.  Life in the seas back then must have been risky business.  If ever time travel is invented, I'd love to go back and see it for myself -- preferably from a safe distance.  And as interested as I am, I doubt I'd be donning my scuba gear to get a closer look.

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The painted bones

It's fascinating how long into our past we've had rituals surrounding death.

There's decent evidence that our cousins the Neanderthals -- which went extinct on the order of forty thousand years ago -- buried their dead, and used ceremonial pigments like red and yellow ochre to decorate the bodies.  What I'm curious about is if those rituals were performed purely as fond remembrance of the the person who had died, or if it had a more religious significance.  Did they believe in an afterlife?  Was the reverence shown to a dead person's body because of belief that the person's soul still, in some sense, inhabited the remains?  Or some other reason entirely?  

It's all too easy to misinterpret the tangible evidence left behind, even from the relatively recent past.  Take, for example, the practice -- most common in Scotland and England -- of placing sturdy metal cages over grave sites.  The more fanciful-thinking believe it was because of a fear of vampires or zombies -- to protect the living from the dead.

A "mortsafe" in Cluny, Aberdeenshire, Scotland

The real reason -- which we know from the writings of the time -- was that it was actually to protect the dead from the living.  Grave robbing was common in the seventeenth and eighteenth centuries, not only to steal any valuables the person might have been buried with, but to sell the corpse itself to medical or anatomical laboratories for dissection.  (Recall the early nineteenth century Burke and Hare murders, where a pair of enterprising young men decided it was more lucrative to kill people themselves and sell their bodies than to wait for them to die; Hare turned King's evidence in exchange for immunity if he testified against Burke, which he did.  Burke was hanged -- and in a grisly but ironic twist, his body was given to an anatomical laboratory for dissection.)

So it's harder than you'd think to ascertain the motives people had for certain ritual practices in the past.  As far as the decoration of bodies by the Neanderthals, of course, at this point it's impossible to know.  But it's fascinating that our (very) distant ancestors had burial rituals not so very different from our own.

A recent find in Turkey has shown that modern humans have been doing this sort of thing for a very long time as well.  Çatalhöyük, nicknamed the "oldest city in the world," has provided fascinating archaeological finds before; the "Mother Goddess of Çatalhöyük," a six-thousand-year-old ceramic statue probably associated with rituals of fertility (sex being the other thing people have been obsessed with for a long time) is probably the most famous artifact from the site.  (If you're wondering how Çatalhöyük is pronounced -- heaven knows I was -- I'll save you the trouble.  Near as I can get, it's something like "chot-al-hoik.")

[Image is licensed under the Creative Commons Nevit Dilmen, Museum of Anatolian Civilizations 1320259 nevit, CC BY-SA 3.0]

A new find at the site, though, is equally interesting.  A team from the University of Bern has uncovered nine-thousand-year-old bones -- so a full thousand years older than the Mother Goddess figurine -- that show evidence of having been painted.  Not only were they painted, they appear to have been unearthed more than once, and repainted.  Fascinatingly, they used different colors for different genders -- cinnabar/red for males, copper-bearing minerals/blue and green for females.  Not all the bones were so decorated; it may have been a mark of status, or membership in a ruling class or priestly class, but all that is speculation.  (The fact that there have been painted bones of children found suggests that it wasn't mere individual status that was the deciding factor.)

There's also an association between the number of painted burials in a building, and the amount of painted decoration on the walls.  "This means when they buried someone, they also painted on the walls of the house," said study senior author Marco Milella.  "Furthermore, at Çatalhöyük, some individuals stayed in the community: their skeletal elements were retrieved and circulated for some time, before they were buried again.  This second burial of skeletal elements was also accompanied by wall paintings."

I'd like to think that the painted bones were a sign of reverence and not fear of retaliation by an angry spirit, but that too is speculation.  All we have is the artifacts to judge by.  Even so, it's fascinating to get a glimpse into the distant past of our own species.

And you have to wonder what our distant descendants will make of the artifacts left from our own society.  What will they think of the marble and granite monuments we raised over the dead?  It puts me in mind of the eerie, atmospheric rhyme I saw on a gravestone in the cemetery in Waynesburg, Pennsylvania where my great- and great-great grandparents are buried:

Remember, traveler, as you pass by,
As you are now, so once was I;
As I am now, so you will be;
Prepare for death, and follow me.

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