The Sad Case of the Orthodoxy and the Posth Article on Pleistocene Demographics

Just a couple months ago, in the context of the peopling of Ireland, I emphasized on Eupeida (and here) how important it is to put all the Theories Du Jour that are based on modern uniparental distributions through a model based on population demographics and sound logic.

Specifically, I emphasized that ancient population sizes were minuscule compared to modern ones, and that if a population started a long long time ago, with a size that was way way small -- compared to subsequent waves -- that it would give a false signal that the original population was "conquered" or "outcompeted" or "never existed" or originated somewhere incorrect.   I cautioned against those four errors.  

This engendered quite the debate on Eupedia forums.  When backed into a corner and shown the weakness of his "R1b Were Studly Conquerors Theory," the "blindly following the current orthodoxy" folks react badly.
 
Many "Interwebz Scientistz" fail to grasp these concepts.  They favor their own wacky, biased theories based on what they see today only.  If a land is populated by one people, they must be all conquering studs, right?

Today, Posth et. al put out an extensive paper on Pleistocene demographics.  

Its shocking discovery?  Just like Y DNA Hg C existed in Europe in tiny numbers among the very first Europeans, so did mtDNA Hg M.

M disappeared eventually, due to the simple fact that its initial population size was tiny, and that because it had been there so long, the odds that certain women didn't have daughters, each generation, eventually meant it was not passed on.  Remember, we're talking uniparental markers here.  

The authors commented exactly as I did: up to now, people mistakenly believed that Hg M never set foot in Europe -- or that if it did, it was killed off or whatever by a new wave.  Sorry, both theories are wrong.

It is WONDERFUL to see another peer-reviewed, scholarly paper making this exact same point, and backing it up with newfound data.

As the paper indicates:

-These first hunter gatherers started with a TINY initial population size.

-There is a loss every generation of males having males or females having female offspring.

-I've calculated the approximate odds of a male not having a male child or a female not having a female child (i.e. looking like their uniparental marker was "conquered") at 12.5%, each generation, totally random.

-The longer a population has existed in a locale (and being free of mutations), the more generations go by, the greater the chance that random happenstance, chance, etc. will make it appear that a Hg either never existed or was slaughtered in a mass killing/enslavement/mate preference.

Now you have further proof of it.

I'm waiting to hear how Hg M died out because of some studly new more beautiful females who moved in.  Oh woops, Maciamo doesn't post here.  And he doesn't himself bear Hg M.  And M is not linked to R1b...

A Proposal for a New Lexicon for Ancient DNA "Components" Like WHG, EHG, EEF, ANE, and CHG

Some of us a few years back started to decry the ever-ongoing ISOGG renaming process, which coupled with the discovery of new subclades, meant that one year, someone might be deemed R1b1b1a2bab2ba11babd12ba2b1c, and the next year R1b1b2bab2f1faf1fafaf1f1f1a. 

People started saying that it would probably be better to say the first couple letters and the major terminal SNP. For example, R1b-U106 or I2-M26. This was logical and good.  Unlike the terminology, the SNPs never change. And they're shorter to write.
  
Here I humbly propose a new terminology for ancient autosomal samples. I think picking terms like, "WHG" was a mistake, and now that I read about EHG and CHG, I really think so. For the uninitiated, these acronyms stand for "Western Hunter Gatherer," "Caucasus Hunter Gatherer," etc.

People compare their modern genomes, or the genomes of modern populations or ethnic groups, to these ancient samples. And then they use the shorthand, like, "Scottish average 19% CHG." This is highly misleading.
 
Let me give the reasons why I think it is deficient, and tell me if you disagree.
 
1. As we get more samples over time, it will be hard to keep renaming the different samples, if they form a different component. We just saw this with the recent CHG finds. Imagine if we find a detectable signal of ancient genes from Iberia. What will we call that component? "Really Western Hunter Gatherer?"
 
2. The shorthand is deeply misleading (i.e., "Scottish are 19% CHG.") This to me is the most important point. Most people reading this are experts. But I see on so many other boards people who seem to think that some scientist somewhere took a survey of a bunch of ancient samples, "averaged" it, and that we are comparing populations to populations.

We're not. We are not comparing Scots to Western Hunter Gatherers. We are comparing Scots (or any other modern individual or group) to ONE SAMPLE. For WHG, it's Loschbour. For EEF, it's Stuttgart. For ANE, it's Mal'ta. Etc.

3. We don't know that that one sample will turn out to be representative of "Western Hunter Gatherers" any more than we know that taking Danny Devito or the harlequin model Fabio is a representative of a modern Italian. Indeed, as the number of samples we get grows, we know the situation is infinitely more complex.

We all remember, for example, when the first farmers sampled had very unique mtDNA. For a while, people tried to read too much into it. "OMG, what if all farmers bore this odd mtDNA?" was the refrain. But it turned out to be a one-off. This can and will happen again and again as we get more samples over time.

4. The acronyms will get repetitive real fast. We are talking about aDNA, remember? Before farming, the whole world were hunter gatherers. So, many (most) aDNA samples will eventually have -HG after them, if we follow the current convention.

I imagine a world where we have found 26 slightly different hunter gatherer samples, and thus we have one different -HG for every letter in the alphabet! That'd be just silly.
 
For these reasons, but primarily numbers 2 and 3, I think the current practice is misleading and doomed to failure. Europe is a very complicated place. We will find ancient samples with very unique genomes, which are detectable in modern populations. They will all be slightly different from one another, because one sample is, well, one sample... It is highly misleading to say that "John Smith..." or "Estonians are more Western Hunter Gatherer than..." because we have not sampled all, most, or even many Western Hunter Gatherers. (I don't mean to pick on WHG. This applies equally, indeed MORE, with EEF and ANE!)

So, what is the solution?

I think if we purport to be scientific, we need to speak with scientific precision.

If an individual or a modern population bears resemblance to an ancient genome, we should state that it has a percentage similarity to that one sample. And not try to make it more than it is, like the very official and extensive term like, "Eastern Hunter Gatherers."

As for the sample, we should also include the year discovered, the situs of the discovery, and the years Before Present (BP). 

Remember, many of these sites are caves where there have been and will be more discoveries. In other words, I expect there will be many more Loschbours, more Stuttgarts, etc., and it will get quite confusing unless we speak with specificity about when something was discovered and when in time it came from.
 
Let's avoid a situation like we had with terms like R1b1b1b1a2a1b2bc3d, which lose meaning. Let's refer to things with scientific precision.

Examples:

Instead of, "Scots are 19% Ancient North Eurasian."

SAY: "On average 19% of the genes of the modern Scottish population match 2013Mal'ta-24,000BP."

Instead of, "Southern European populations have a lot more CHG blood than I expected."

SAY: "Southern European populations bear many genes matching 2015Kotias-10,000BP."

Instead of, "Sardinians are 45% WHG."

SAY: "Approximately 45% of the genes in the modern Sardinian population resemble 2013Loschbour-6000BP."


This convention is much more accurate.

Ancient DNA Provides A New Understanding of Haplogroup I2a1a M26

Below is a map of confirmed instances of I-M26 found in prehistoric remains.  Lots of others could have potentially been added -- ancestral clades, closely related sister clades, and ones where the coverages is insufficient to determine whether it is indeed M26 (or L672 L160 etc.)  But we decided to err on the side of being conservative.

Going chronologically, we have M26 in what is now Sweden, at the Motala site, at 7730 BP (Before Present).  These were Hunter/Gatherers.

Next, we have it at the La Spina site, in modern Spain, at 5765 BP.  This was a Megalithic site, during the Neolithic.  Farming was already in Spain at that time.

Next we find it at Treilles, modern France, at 5015 BP.  This was a Megalithic/Neolithic site of farmers, near the coast.

Next we find it in the Remedello culture, of Northern Italy, at 4758 BP.  This was a Chalcolithic (Copper Age) site.  Per Robert S.P. Beekes, "bears all the marks of an Indo-European invasion: a new style of ceramics, a new burial rite, changes in the social structure, the introduction of a warrior aristocracy, the intro- duction of metallurgy, the horse and the chariot. But it is still not possible to assign language groups to particular culture."

Finally, for now, researchers have found it in the Megalithic culture of central France, near the Dolmen of Villaneuve-Sur-Yonne, 4753 BP, and again, of course, farming was present.  

In modern times, we find M26 at 37% in Sardinia, certainly an outlier due to substantial founder effect.

But it is also found at up to 10% in Samnite country in Molise, Italy (and in significant numbers in Cosenza province of northern Calabria).  It is found at 5-9% in Spain, including Basque country.  At up to 7% on Sicily.  And 3% in many areas of England and Ireland, especially places like the Channel Islands.  It is still found at 1% in Southern Sweden.

So, given all that we know, what is a sensible theory for M26's distribution and spread?  

We've heard them all, and each has merit: that is represents Megalithic Mariners, who went around old Europe converting local populations and building huge monuments like Stonehenge and the Nuraghe.   That it represents the spread of Cardial Ware culture, along the western Mediterranean seaboard.  That it represents the spread of farming, either as hunter/gatherers who adopted farming quickly, or as a rare clade of Haplogroup I that was predominantly farmers since the dawn of agriculture.  Finally, some posit that it represents a caste (or not) of people embedded in other haplogroups in motion, most often listed as G2a or R1b.

All have merit, none are perfect.  Let's go through the logical conclusions and form a model.

The presence of M26 amongst the hunter/gatherers of Motala, and its widespread ancient distribution by the dawn of the Neolithic tell us that it is a most ancient indigenous European clade.  

We believe that it is safe to say that the first modern humans in Europe, Aurignacians, aka Cro-Magnons, bore haplogroup C.  (Although during the Paleolithic, that far back, it is really anyone's guess whether Hg C came in during one the next phases).

M26, along with its brother clades within Haplogroup I2, most likely formed a part of the second wave of European hunter/gatherers, and was presumably present among the Epi-Gravettians and the Magdalenians.

How then does one explain its wide distribution and adaptive nature throughout the continent during the Neolithic? 

Perhaps the answer is simple.  These were people who have been in Europe for a long time, and are adaptable, and are survivors.

Europe was settled in waves, and not just the three big ones (Hunter/Gatherer, Farmers, Steppe Horsemen), which is an oversimplification.  

Imagine Europe as a pipe.  It has three entry points: the steppes of Russia from people heading due west, the Balkans/river corridors from people heading northwest, and the Mediterranean from people heading north.

Imagine a party.  The "Emtwentysix" family was among the first to arrive.  When they got to the house, they represented maybe 15% of the guests.  But as more guests arrived, some through the front door, some through the back door, and some through the side door, the Emtwentysix family became a smaller percentage of the total guests, now just 0.5-3%.  

When the family arrived, they were playing foosball together.  But at some point, some members of the family joined a group of other guests who were dancing, and some joined groups of other guests who were playing video games.

You get the analogy.  

None of the above theories may be 100% accurate, and yet all theories may be accurate in their own way. 

For example, it is doubtful that I-M26 first showed up in Europe with the Cardium Pottery culture, but it could have been among the groups (as it was clearly in Italy for a long time) that encountered the Cardial peoples, and then became a component of said peoples, heading west along the western Mediterranean seaboard.  

Similarly, in Northern Italy, M26 peoples could have been among the first who were Indo-Europeanized, in the Remedello culture, and then part of the secondary expansion into Italy, which formed the Oscan-speaking Sabellic tribes (Samnites, Brutti, and Sicels).  

In other places, clearly M26 was Megalithic acculturated, and its odd distribution in places where Megaliths appear is intriguing for sure.  

And lastly, some of its distribution could reflect later movements by obsidian traders or something similar.

Prehistory is a series of periods of demographic expansion followed by demographic crisis.  Good hunting, good weather, good crops, absence of disease, and other factors make people have more babies.  Then luck turns, and some lines die out, while other lines come to the party.  Since the Bronze Age in Europe, it has mostly been a demographic march to more population as time goes by.  

We would like to see a study comparing the M26 in Sweden, Ireland, Spain, the Italian mainland, and Sardinia, to see who is ancestral to whom, or how and when the different groups separated.

But the bottom line appears to be that M26 has been in Europe a long time, and like all lineages that were there a long time, its distribution will have changed a bit and its absolute numbers will have gone down, but these Most Adaptable Hunter Gatherers (MAHGs) continue to intrigue.