I’m a big fan of Steven Pinker. But I’ve become much more pessimistic than him over the past few years. Here’s hoping that Enlightenment Now turns that around.
DNA Geeks has a total site redesign! Check it out.
I haven’t been saying this on the podcast yet, but you should be subscribing to it on iTunes, Stitcher, and Google Play, and review and rate it. Spencer and I have a certain audience already, and we’d like to expand it.
This has probably always been so, but I’m really getting tired by the emergence of different verbal ticks in various socio-political subcultures. For example, when liberals say “my dude” -“bros”, it’s dismissal-by-identity. Both NRx, and what is now called the Altright, also have their own subculture languages, which makes understanding what they’re trying to say hard for outsiders. A feature or a bug?
In human populations a SNP in ABCC11 is correlated with two salient traits: 1) wet or dry earwax 2) body odor. When I had my first son sequenced before his birth the main variant of phenotypic consequence that I noticed (aside from him being a heterozygote on KITLG), was that he carried a derived mutation on this position. Meaning that he was going to have dry earwax and fewer issues with body odor.
My wife and I are both heterozygotes. This is not too surprising. The derived variant is actually greater than 50% in Bengalis in the 1000 Genomes (in South India the derived variant is also around ~50%), while about ~25% of Northern Europeans are heterozygotes.
There’s another reason few Chinese consumers buy deodorant: basic biology.
Scientists in recent years have shown that many East Asians, a group that includes China’s ethnic Han majority, have a gene that lowers the likelihood of a strong “human axillary odor” — scientist-speak for body stink.
That lowers the likelihood that they will use deodorant to begin with, according to a 2013 study by researchers at the University of Bristol and Brunel University in Britain, after a survey of nearly 6,500 women of various backgrounds.
“It is likely that deodorant usage is not widely adopted because there is, for much of the East Asia population, no need for it,” it said. (For those curious about such matters, that same genetic difference also leads to drier earwax.)
A friend of mine in undergrad of East Asian background told me once that she had never worn deodorant. So this shouldn’t be very surprising.
The correlation between carrying the G, ancestral, allele, and body odor is very strong. Though it is imperfect. Going through this literature human smells are clearly a polygenic trait (see The effect of ethnicity on human axillary odorant production). That being said, this case-control study in a Han population shows ABCC11‘s importance in at least East Asian populations (earlier work in Japan showed that those with body odor tended to have wet earwax and carry the G allele as well).
In regards to the genotype proportions the authors observe:
The excessive heterozygosity observed in AO individuals is probably due to the effect of selection, particularly nonrandom mating against AO phenotype.
This doesn’t make sense to me. Wouldn’t people who have body odor tend to pair up in a society where they are a minority? The authors note that the excess of heterozygotes was observed in earlier studies too.
If you dig into the frequencies it seems that the derived mutation is absent among populations in Africa without recent Eurasian back-migration. I looked it up, and it’s segregating in ancient Eurasian samples, with Ust Ishim being a heterozygote. It is curious that in no population has the derived frequency swept to fixation, nor has the ancestral variant fixed in other groups (such as in Europe).
I strongly doubt that there is any selection on this locus due to earwax or body odor. It is a pleiotropic locus, there are other effects from the mutation. One of those other effects is probably the target of any selection. And in regards to selection, it seems likely that that would be a balancing sort since neither the ancestral nor the derived variant are fixed in most populations.
Literally hundred of thousands of people have read my post, 1 in 200 men direct descendants of Genghis Khan, since 2010. It was based on the paper The Genetic Legacy of the Mongols*, which reported that one particular Y chromosomal lineage was very common in Central Asia, and, that it exhibited hallmarks of explosive growth over the last thousand years.
The Y-chromosome haplogroup C3*-Star Cluster (revised to C2*-ST in this study) was proposed to be the Y-profile of Genghis Khan. Here, we re-examined the origin of C2*-ST and its associations with Genghis Khan and Mongol populations. We analyzed 34 Y-chromosome sequences of haplogroup C2*-ST and its most closely related lineage. We redefined this paternal lineage as C2b1a3a1-F3796 and generated a highly revised phylogenetic tree of the haplogroup, including 36 sub-lineages and 265 non-private Y-chromosome variants. We performed a comprehensive analysis and age estimation of this lineage in eastern Eurasia, including 18,210 individuals from 292 populations. We discovered that the origin of populations with high frequencies of C2*-ST can be traced to either an ancient Niru’un Mongol clan or ordinary Mongol tribes. Importantly, the age of the most recent common ancestor of C2*-ST (2576 years, 95% CI = 1975–3178) and its sub-lineages, and their expansion patterns, are consistent with the diffusion of all Mongolic-speaking populations, rather than Genghis Khan himself or his close male relatives. We concluded that haplogroup C2*-ST is one of the founder paternal lineages of all Mongolic-speaking populations, and direct evidence of an association between C2*-ST and Genghis Khan has yet to be discovered.
The primary aspect here seems to be pushing the age back. The Mongols, or what became the Mongols, were a marginal group of tribes when this variant arose. There is some citation of the fact that some putative descendants of Genghis Khan don’t even carry the “Star Cluster”, but there are other papers which report even different haplotypes! So I’m not sure that that is dispositive in any sense.
Perhaps the true question now is why this cluster expanded so much over the past 2,500 years or so? There are plenty of candidates historically, but being Bayesians we should be cautious about overturning prior hypotheses on new data. Coalescence dating in particular is often an art as opposed to a science (I don’t mean this literally, but anyone who has used the programs mentioned in the paper knows what I mean).
An alternative model is that as a null we should expect star clusters now and then. But most people don’t seem to think that rapid expansion of Y chromosomes during the Holocene is simply a matter of chance as opposed to necessity.
* My boss and friend, Spencer Wells, was a coauthor on the paper.
Spencer and I are doing a Facebook live AMA at 2 PM EDT/1 PM CDT/12 PM MDT/11 AM PDT on the 1st of February (tomorrow as of when I’m writing this). People will ask us questions, and the questions will be relayed to us, and we’ll answer live on video.
One of the first things I wrote at length about historical population genetics, in late 2002, happened to be a rumination on the Y chromosomal phylogeography of Finnic peoples. At the time there was debate as to the provenance of the N1c Y chromosomal haplotype (this is the haplotype of the Rurikids by the way). Just as R1b is ubiquitous in Western Europe, and R1a in Eastern Europe (and to some extent in Indo-Iranian lands), N1c has an extensive distribution in the northern zone of Eurasia.
The question at the time was whether N1c was from Europe and in particular the Finnic peoples, or, whether it was from Siberia.
NJ Tree of Pairwise Fst
Today we have many of the questions resolved. At this point, we know that the Finns, Sami, and Estonians, all exhibit evidence of gene flow from a Siberian-like population. This is clear on any genome-wide analyses. Though this is very much a minority component, even among the Sami, because it is genetically very different from the Northern European background, it is clear on any analysis.
We suggest that the Siberian and East Asian related ancestry in Estonia, and Y-haplogroup N in north-eastern Europe, where it is widespread today, arrived there after the Bronze Age, ca. 500 calBCE, as we detect neither in our Bronze Age samples from Lithuania and Latvia.
This is not the only ancient DNA paper that shows this. Of course, sampling is imperfect, and perhaps they’ve missed pockets of ancient Finnic peoples. But the most thorough analysis of Mesolithic hunter-gatherers in Scandinavian does not pick them up either, Population genomics of Mesolithic Scandinavia: Investigating early postglacial migration routes and high-latitude adaptation. Populations, such as the Comb Ceramic Culture, which have been identified as possible ancestors of the modern Finnic culture and ethnicity, lack the distinctive Siberian-like component.
At the SMBE 2017, I saw a poster which had results that were sampled from Finland proper, and distinctive ancestry of Siberian-like peoples was present in an individual who lived after 500 AD. This means that in all likelihood the circumpolar Siberian population which introduced this new element into the East Baltic arrived in the period between 500 BC and 500 AD.
Someone with more knowledge of paleoclimatology and archaeology needs to comment at this point. Something happened in this period, and it probably left a big ethno-linguistic impact. But I don’t know enough detail to say much (the Wikipedia entries are out of date or don’t illuminate).
I will add when I run Treemix Finns get the Siberian gene flow you’d expect. But the Lithuanians get something from the Finns. Since the Lithuanians have appreciable levels of N1c, that is not entirely surprising to me (the basal flow from the Yakut/European region to Belorussians may be more CHG/ANE).
Additionally, I will note that on a f-3 test Lithuanians have nearly as high a z-score (absolute) as Swedes (i.e., Finn; Swede/Lithuanian, Yakut), indicating that the predominant Northern European ancestry isn’t necessarily Scandinavian, as much as something between Lithuanian-like and Swedish-like (on Admixture tests the Finns do seem to have less EEF than Swedes, and Lithuanians probably the least of all among non-Finn peoples).
Addendum: I should note here that the genetics is getting clearer, but I have no great insight into the ethno-linguistic aspect. Perhaps the Siberian-like people did not introduce Finnic languages into the Baltic. Perhaps that was someone else. But I doubt it. That being said, though the Siberian-like component adds great distinctiveness to the Finns, it is important to add that by and large Finns are actually generic (if highly drifted) Northern Europeans.
I have mentioned before that the 1000 Genomes Chinese are heterogenous. Many of the ones sampled in Beijing are North Chinese. But there is structure within the South Chinese samples as well. The PCA above shows it. I’ve pruned some of the data for clarity (it’s probably a cline really, with cut-offs and breaks happening because of variation in population density)
Nothing surprising in the Fst matrix. The two South Chinese groups are close to each other, while the North Chinese are shifted toward the Koreans, who are shifted toward the Japanese.
Admixture analysis shows that the two South Chinese groups can be modeled as a mix of North Chinese and the Dai people of southern China, who are ancestral to the Tai people of Southeast Asia. The “South China 2” cluster is somewhat more Dai than the “South China” cluster proper.
The Miao/Hmong samples from the HGDP are very similar to the South China cluster in admixture analysis (and less Dai than the South China 2 cluster). This is not surprising, as the Miao/Hmong are relatively recent migrants into Southeast Asia from China.
What does Treemix say? Basically, the two South Chinese clusters seem to differ mainly in their Dai proportions (as admixture would imply). They could be on the same cline, and the perception of structure might be an artifact.
What is a species? I don’t know. And honestly, I don’t really care too much.
Species is just a semantic label I place on a set of individuals related to a phylogeny. There tends to be a correlation in genetic variants between these creatures. For sexual organisms, which does not include all organisms, it generally denotes the ability to produce fertile offspring between any two pairs of the opposite sex.
Over ten years ago I read Speciation by Jerry Coyne and H. Allen Orr. As evolutionary geneticists with an interest in taxonomy they take the “species problem” somewhat seriously, but ultimately they’re instrumentalists. “Species” are not the ultimate goal of their scholarship from what I can tell. Rather, species are instruments, semantic tools to smoke out evolutionary processes which shape and determine the pattern of biological variation we see around us. The “origin of species” is less important in relation to the species themselves, as opposed to why we can create categories of species out of the specialized morphological diversity around us.
Not everyone agrees with this position. And not everyone has the same opinion about species. On the whole plant systematists and ecologists will take a different tack on the species problem than evolutionary geneticists. Evolutionary geneticists who work with plants will have a different view from those who work on animals, let alone those who work with bacteria.
The point then is that species are social constructs whose utility and nature varies by discipline. I’m not being a solipsist here. Nature is real. And genetic and phenotypic variation is real. But in some ways the labels we give it can become matters of emphasis.
Of course, I am aware this is an idiosyncratic view. For Carl Linnaeus, the cataloging of species, natural kinds, was cataloging the Creation of God. If you are a Creationist, as most pre-modern people were, then species in their variety and number reflect the will and intention of God. Their study and enumeration would be a glimpse into the mind of the divine.
This doesn’t come out of a vacuum. The religious and Creationist thought simply systematized deep intuitions about the nature of things and biological categories. One doesn’t have to be a genius to make a story about why it would be adaptive to promiscuously and compulsively categorize nature around you. Religious thinkers were simply reshaping and firming up ideas which were in the air.
And this probably brings up why questions about “species” crop up over and over in the comments. And this is why a few times a year I have to put this post up….
Dienekes Pontikos resurfaces with a post, Out of Africa: a theory in crisis. The title is a bit hyperbolic. But in Dienekes’ defense, he’s been on this wagon for over ten years, and the evidence is moving in his direction, not against him. I think a little crowing is understandable on this part.
With that being said, I think the biggest rethinking that we’re doing is less about where modern humans arose (Sub-Saharan Africa, North Africa, the Middle East), but how they arose. Some geneticists are quite open to the idea of Eurasian (Neanderthal?) back-migration to Africa several times (and out of Africa several times). Others are positing that a “multiregional” model might actually be about the situation within Africa.
A simple stylized model of a rapid punctuated expansion of humanity which replaces other lineages in toto is no longer likely. There has been widespread admixture, even though the last major demographic wave seems to be overwhelmingly predominant, at least outside of Africa. But the whole process might result in a much more complex history than we had thought.
The multiregional model is probably wrong on the details. The history of our species is not really phyletic gradualism and anagenesis. But there are also many processes and dynamics which a multiregional model takes into account and anticipates that probably are important in a general sense toward understanding the origin of our species.
In Robert Heinlein’s uneven late work Friday the mentor of the protagonist mentions that because of a possible collapse of technological civilization he maintains a collection of paper books.
This crossed my mind when I saw that Storify is shutting down. Or Kevin Drum’s reflections on the changes in blogging.
I’ve put a lot of content out there over the years. Probably on the order of 5 million words across my blogs. Some publications here and there. Lots of tweets. But very little of it will persist into future generations. Digital is evanescent.
One of the things that reading Land of Liberty has prompted in me is the need to read Matt Stoller’s book, when it comes out. Land of Liberty in many ways was a historical foil of Stoller’s article, How Democrats Killed Their Populist Soul.
Steven Pinker’s new book, Enlightenment Now: The Case for Reason, Science, Humanism, and Progress, is now being published a few weeks earlier. Apparently this now one of Bill Gates’ favorite books.
DNA Geeks has a total site redesign! Check it out.
In human populations a 
The fact that platforms tend to disappear has started to make me wonder: what posts should I figure out a way to preserve for posterity?
One of the first things I wrote at length about historical population genetics, in late 2002, happened to be a 
