All in the family

Archaeologists and paleontologists are up against the same problem; bones and other fossils only get you so far.

There are cases where fossil evidence can give you some hints about behavior -- patterns of tracks, for example, or the rare case where the positions of the fossils themselves give you a picture of what was going on, like the recent discovery of an opossum-sized mammal, Repenomamus, attacking a much larger dinosaur, Psittacosaurus.  The pair of fossil skeletons were preserved, locked in a battle to the death -- the death of both, as it turned out, because they were both engulfed mid-fight in a mudslide.

But such lucky finds are rare, and inferences of behavior from fossils are usually sketchy at best.  This is why the study of a group of Neolithic human skeletons found near Gurgy-les-Noisats, France, 150 kilometers southeast of Paris, was so extraordinary.

The level of DNA analysis now possible allowed the analysis of the genomes of 94 of the 128 individuals buried at the site, to the level that the researchers not only were able to construct a seven-generation family tree for them, but make a guess as to what each individual looked like.

The analysis found that the bodies were buried in family groups -- the more closely two people were related, the closer together they were buried -- and that women who were not descendants of the original couple were mostly completely unrelated, suggesting they'd come into the family from another community.  Just about all the males at the burial site, on the other hand, were related, leading the researchers to conclude that men in this community tended to stay put, and at least some women did not.

Another curious thing was that the study detected no half-sibling relationships.  All of the sibling groups were from the same mother and father.  In this family group, at least, monogamous relationships were the norm.

Of course, there's a lot we still don't know; while this is a stunning accomplishment, it still leaves a great many questions unanswered.  For example, were the "outsider" women brought in because of a custom of outbreeding, or by conquest/capture?  What were the religious practices and beliefs that led these people to bury family members near each other?  Was the monogamy shown in this family universal in this culture, or was this grouping an exception for some reason?

It's an intriguing piece of research.  "This type of work really breathes new life into our understanding of ancient peoples," said Kendra Sirak, an ancient-DNA specialist at Harvard Medical School in Boston, Massachusetts, who was not involved in the study.  "I'm especially curious about the man at the root of the family tree.  I would love to know what made this person so important."

And given that a significant percentage of my ancestry comes from central and western France, I have to wonder if anyone in this family tree is a direct ancestor of mine.  There's no way to find out, of course, but the thought did cross my mind.  It's kind of eerie to think when I look at those facial reconstructions, one of those faces looking back at me might be my great-great (etc.) grandparent.

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Out of the ashes

The eruption of Mount Vesuvius in 79 C. E. and its destruction of the cities of Pompeii and Herculaneum make for a story that is as fascinating as it is horrific.

Vesuvius is a stratovolcano, built up from layer after layer of hardened lava (the "strata" of the name).  Stratovolcanoes usually produce felsic lava -- high in silica content -- making the molten rock thick, viscous, and resistant to flowing.  The results are explosive eruptions, not the cascading rivers of lava you see in shield volcanoes such as Kilauea, which produce mafic lava that is low in silica and flows readily.

The eruption of a stratovolcano is catastrophic.  Unlike the Hawaiian shield volcanoes, which certainly can cause significant property damage but seldom loss of life, stratovolcanoes fling chunks of rock around, generate huge amounts of ash, and -- worst of all -- can create pyroclastic flows of superheated air that can move at a hundred kilometers per hour and incinerate everything in their path.  It was a pyroclastic flow from Mount Pelée that killed almost thirty thousand people in only a few minutes on the island of Martinique in 1902; one of three people in the city of Saint Pierre who are known to have survived only did because he was being held in an underground jail cell.

The combination of rock ejection, ash clouds, and pyroclastic flows are sometimes called Plinian eruptions after the Roman author Pliny the Elder, who died during the eruption of Vesuvius.  If you don't mind being a little freaked out by the power of nature, check out this ten-minute video simulation of the 79 C. E. eruption, from the perspective of a person in Pompeii:

The reason the topic comes up is because of a paper that appeared last week in Scientific Reports about some research done by a team led by Gabriele Scorrano of the University of Copenhagen.  Scorrano and his team found two human skeletons, one male and one female, that -- despite being covered by scorching-hot ash and then entombed for almost two thousand years -- contained enough intact DNA to analyze.

The man's, in fact, was complete enough to do a whole-genome analysis, including a Y DNA and mitochondrial DNA study.  The results were interesting, if not surprising; his DNA was similar to that of modern Italians from the region, although both his Y DNA and mtDNA showed markers most commonly found on the island of Sardinia.  

So he likely had ancestry on both sides of his family from Sardinia.  He also, apparently, had tuberculosis.  The woman's skeleton, which contained only fragmentary DNA, showed signs of significant osteoarthritis.  Serena Viva of the University of Salento, who co-authored the study, said, "This could have been the reason for which they waited for it all to finish, maybe in the security of their home, compared to other victims who were fleeing and whose remains were found in open spaces."

The ruins of Pompeii, with Vesuvius in the background [Image licensed under the Creative Commons ElfQrin, Theathres of Pompeii, CC BY-SA 4.0]

Scary stuff, that.  I have to say I'm glad I don't live in Naples; I wouldn't be able to sleep with Vesuvius looming over me, even though it's shown no signs of an imminent catastrophic eruption.  I actually thought the same thing when we were in the Pacific Northwest last week, not only because of nearby stratovolcanoes like Mount Rainier, but because the entire area is at risk of enormous earthquakes because of plate movement along the Cascadia Subduction Zone. 

I know the risk during any given week is extremely low, but it did make me a bit nervous anyhow.  Sometimes a little knowledge can be a lot scary.

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Chewing gum and talking about talking

Earlier this week I looked at three cool archaeological discoveries -- cave art in Indonesia, and two finds in Egypt, one of a bone from someone killed in the battle recorded on the Rosetta stone, and the other about a researcher who found that the practice of tattooing has been around for a very long time.

But we're not done with mind-blowing archaeological stories, apparently, because there are two more that I just found out about, and which (if anything) are even cooler than the ones I wrote about Monday.

I learned of the first one from my friend, novelist and blogger Andrew Butters, whose blog Potato Chip Math is a must-read.  In this one, we find out that a team of geneticists have sequenced the DNA of a girl who lived in Denmark 5,700 years ago...

... from a wad of chewing gum.

Well, technically, it was birch sap, but same idea.  They were able to extract her DNA from the gum and sequence her entire genome, which allowed them not only to figure out what ethnic group she was from, but to make a good shot at her appearance.  She had dark skin and hair, they found, and blue eyes.  Here's an artist's reconstruction of what she might have looked like:

[Reconstruction by Tom Björklund]

The authors write:

Analysis of the human reads revealed that the individual whose genome we recovered was female and that she likely had dark skin, dark brown hair and blue eyes.  This combination of physical traits has been previously noted in other European hunter-gatherers, suggesting that this phenotype was widespread in Mesolithic Europe and that the adaptive spread of light skin pigmentation in European populations only occurred later in prehistory.  We also find that she had the alleles associated with lactase non-persistence, which fits with the notion that lactase persistence in adults only evolved fairly recently in Europe, after the introduction of dairy farming with the Neolithic revolution.

The period she lived in was when northern Europe was taken over by people known as the "Funnel Beaker Culture," so named because of their characteristic narrow-based, highly-ornamented pottery:

The 5,200 year old Skarpsalling vessel [Image is licensed under the Creative Commons Nationalmuseet, Skarpsallingkarret DO-9665 original, CC BY-SA 3.0]

"It is amazing to have gotten a complete ancient human genome from anything other than bone,'' said study lead author, evolutionary geneticist Hannes Schroeder, of the University of Copenhagen, in an interview with Science Alert.  "The DNA is so exceptionally well preserved that we were able to recover a complete ancient human genome from the sample… which is particularly significant since, so far, no human remains have been recovered from the site."

The second story goes back a great deal further in time than the little Neolithic Danish girl, though.  In fact, it kind of crosses the line from archaeology into paleontology, because in a paper in Science Advances we find out that the ability to speak might have been around in primates for twenty million years.

The study, led by Louis-Jean Boë of the University of Grenoble, analyzes the mechanics of human speech, in particular how the morphology of the mouth, trachea, and larynx allow for the production of meaningful sound.  It's been thought for years that the advent of speech occurred when our ancestors' larynxes (voice boxes) gradually moved downward, pulling the back of the tongue backward and downward as well and giving the tongue more mobility to shape sounds.  But what Boë's team found was that even if you accept that as the hallmark of speech, it goes a long way further back than we'd realized.

"First, even among primates, laryngeal descent is not uniquely human," Boë and his team write.  "Second, laryngeal descent is not required to produce contrasting patterns in vocalizations.  Third, living non-human primates produce vocalizations with contrasting patterns.  Thus, evidence now overwhelmingly refutes the long-standing laryngeal descent theory, which pushes back 'the dawn of speech' beyond ~200 ka ago to over ~20 Ma ago, a difference of two orders of magnitude."

So that means that at least from a mechanical standpoint, our distant ancestors had the capacity for speech.  Whether their brains were developed enough to say anything particularly interesting is still a matter of conjecture.  But evolution is all about minuscule gains.  Once the upper respiratory tract becomes capable of modulating sounds in a meaningful way, this puts selective pressure on the brain to refine its ability to understand and convey meaning with those sounds -- which puts pressure on the vocal apparatus to become better at producing subtle differences in sounds, and so on and so forth.  Which, as comedian Paula Poundstone notes, may not be entirely a good thing:

Be that as it may, it's a pretty cool discovery.  As I pointed out in Monday's post, it's incredible how much we can infer about our distant ancestors' appearance, culture, and abilities from evidence that would have been a closed book only ten years ago.  Our techniques for carrying out this research are only going to improve, so keep watching the journals -- my sense is that the amazing discoveries in this field have only just begun.

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This week's Skeptophilia book recommendation is pure fun, and a perfect holiday gift for anyone you know who (1) is a science buff, and (2) has a sense of humor.  What If?, by Randall Munroe (creator of the brilliant comic strip xkcd) gives scientifically-sound answers to some very interesting hypothetical questions.  What if everyone aimed a laser pointer simultaneously at the same spot on the Moon?  Could you make a jetpack using a bunch of downward-pointing machine guns?  What would happen if everyone on the Earth jumped simultaneously?

Munroe's answers make for fascinating, and often hilarious, reading.  His scientific acumen, which shines through in xkcd, is on full display here, as is his sharp-edged and absurd sense of humor.  It's great reading for anyone who has sat up at night wondering... "what if?"

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