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April 24, 2019

The Genetics Of The St. Thomas Christians, part 2

Filed under: Indian Genetics,Nasrani,St. Thomas Christians — Razib Khan @ 10:34 pm

Last year I posted The Genetics of the St. Thomas Christians. Recently I got some more samples. Of these, four were clearly self-identified as Southist/Knanaya Christians (as opposed to Northist Christians). The Knanaya are a bit different in their traditions than the broader much larger St. Thomas Christian community.

In the PCA above the bottom left are Middle Eastern groups. Druze and Yemeni Jews. Toward the top are Lithuanians. Green are Iranians. From the bottom right, up a diagonal axis, you see south-north Indian cline from low caste Telugu Christians, to Jatts from Punjab.

It does seem in relation to the other more generically labeled St. Thomas Christians the four Knanaya show some noticeable Middle Eastern shift.

Here’s an admixture plot:

The St. Thomas Christians have more yellow “Druze” cluster than other South Indians, with variation (the Knanaya have more).

I ran some Treemix. Didn’t detect major gene flow, but the Knanaya group was different from the other St. Thomas Christians, having a closer position to West Eurasians. When I ran a three-population test, it was the St. Thomas Christians (Nasrani above), and not the Knanaya, which registered admixture with Middle Eastern groups. It’s probably an artifact that the latter was not detected.

The Christians of Kerala are very similar to other peoples of Kerala. But, I now think it is more than 50% likely that they do have detectable Near Eastern ancestry above what you should expect.

 

The Insight Show Notes — Season 2, Episode 24: Deconstructing the Denisovans

Filed under: Denisovans,Podcast,science,Uncategorized — Razib Khan @ 2:55 pm

The Insight Show Notes — Season 2, Episode 24: Deconstructing the Denisovans

The Dali skull, 200,000 years old. A Denisovan?

This week on The Insight (Apple Podcasts, Spotify, Stitcher and Google Podcasts) Spencer is back, as we go back to our old two-man show format (at least for this episode). We discuss “deconstruct” the Denisovans, one of the newest human species discovered by science.

The Altai

But before we dug into the paleogenomics, Spencer discussed the human and physical geography of Inner Asia, and in particular the Altai region. In the 1990s Spencer had the opportunity to sample the native peoples of the region, which eventually turned in the Eurasian Heartland paper.

We put the critical role of Inner Asia in a broader historical perspective, from the early Indo-Europeans, down to the Mongols and Turks, and finally the “Great Game” of geopolitical rivalry between Britain and the Russian Empire in the 19th century.

The Altai in many ways has been at the center of Inner Asia. Spencer reflects on the fact that this is where there are Shambhala is often located, a mythical utopian kingdom. While the region is surrounded by cold deserts and forbidding mountains, with the Siberian vastness to the north, the Altai region harbors some relatively sheltered valleys through which nourishing rivers flow.

Inside the Denisova cave

Denisova cave also happens to be in the Altai. This means that not only has the Altai been of historical and mythic importance, but it has been at the center of the understanding of human evolution, and perhaps at the center of human evolution!

We discuss the multiple Denisovan individuals which have been sequenced from the cave. And, the first human ‘hybrid’, a woman whose father was Denisovan, and whose mother was Neanderthal, ‘Denny.’ Denisova cave was inhabited both by Neanderthals and Denisovans, with the Neanderthals having some evidence of modern human admixture, and the Denisovans Neanderthal admixture (and perhaps late Homo erectus).

But the Denisovans were not just a Siberian species. New work suggests there were three deeply distinct Denisovan populations, at least. The people of New Guinea may have had at least three mixing events with Denisovan people, while the admixture in China is almost certainly from a different Denisovan population than that in Oceania.

Finally, we talk about Homo luzonensis, and what the diversity of human across eastern Eurasia means in relation to what it “means to be human.”


The Insight Show Notes — Season 2, Episode 24: Deconstructing the Denisovans was originally published in Insitome on Medium, where people are continuing the conversation by highlighting and responding to this story.

April 23, 2019

Denisovans and the human story

Filed under: Denisovans,Human Evolution,Neanderthals,science — Razib Khan @ 1:38 pm
The Siberian cave where a new human species was discovered

We are all aware of the iconic fossil finds which mark the various milestones of our understanding of human evolution. The story of how our species became what it is today. Raymond Dart’s Taung Child helped establish that Africa might be the original home of our species. Lucy, which put the spotlight on some of the earliest upright ancestors of hominins. Even frauds like Piltdown Man go down in the history books, at least reflecting something of a particular Zeitgeist, wrong as it was.

And yet our past is haunted by a very small collection of remains indeed. Humans were never numerous (until recently). Our ancestors were fossilized thanks to luck, giving us a sense of the shape their form and bearing. The fossil trail of the upright line of apes which eventually lost their fur, and left Africa two million years ago, is quite tenuous.

Denisovan teeth from which DNA was extracted

But in the 21st-century new varieties of humans, species perhaps, are not discovered just by fossils alone. Rather, genetic science has now become adept at retrieving DNA from even the most ancient of human remains. Geneticists can then reconstruct the history of peoples long gone from their sequence, and compare them to modern people or other ancient genomes.

In the spring of 2010, the first whole Neanderthal genome was published, a landmark in the development of paleogenetics. Of course, Neanderthals have a long and storied history in paleoanthropology. They’ve been dehumanized and rehumanized and dehumanized many times. The surprise results out of the Neanderthal genome was that humans outside of Africa were all related to the Neanderthals. In other words, a few percent of the genome of non-Africans could be attributed to descent from them.

But wait! 2010 had more surprises in store for us. At the end of the year, a paper reported the genome of a new species of human. Previously unknown to science, these were the Denisovans, named after the cave in Siberia in which the remains were found. Because there was a genome of Neanderthals already sequenced, scientists could tell that the Denisovans were closer to Neanderthals than to modern humans. About ~750,000 years ago the ancestors of Neanderthals and Denisovans left Africa, separating from our own ancestors. Soon after, the Neanderthals and Denisovans began to diverge, becoming two distinct lineages, far more distinct than any two modern groups.

But why were they distinct?

To answer the question one must look at a map. While Neanderthals occupied Europe and ranged east into the heart of Eurasia, Denisovans likely inhabited the zone between eastern Siberia down into Southeast Asia. Differences develop between populations with common ancestors when they are geographically separated, and by and large (though not exclusively), Denisovans and Neanderthals were separated by the vast arid heart of Eurasia.

While the Neanderthals were a northern population, despite the discovery of Denisovans in a Siberian cave, they may have been used to warmer climes more often than not.

Papuan Woman and Child

One reason this seems likely is that Denisovans have descendants today. But they are not an obscure group in Siberia…they are the Papuans of New Guinea! This population has about ~5 percent of its genome from Denisovans. The descendants of these ancient people are also more widely scattered across Oceania, though to varying degrees.

While the Australian Aboriginals and Negritos of the Philippines have significant Denisovan ancestry, the native tribes of the Andaman Islands have little. This suggests that not all indigenous peoples of South and South Asia mixed equally with Denisovans.

More recent work has revealed that much lower levels of Denisovan ancestry are present across much of South and East Asia. And, importantly, the Denisovan ancestry in groups like the Chinese seems to be from a different group than that mixed into the Papuans. The genome from Denisova cave likely belongs to the people who mixed with East Asians and contributed adaptative functions such as high altitude adaptation in Tibetans.

So what we know now is that for hundreds of thousands of years a widespread group of humans, Denisovans, occupied eastern Eurasia. Unlike Neanderthals, they were not a single homogeneous group. Some research groups have detected three different Denisovan populations mixing into modern humans, while others have suggested that the Denisovans carry ancestry from even earlier hominins, who likely arrived in Asia before them.

But unlike Neanderthals or our African forebears, we have not been able to reconstruct a full skeleton of an individual who is Denisovan.

There are skullcaps, teeth, and stray bones, but not enough identified remains which could give us a sense of what these people looked like, how they were built (though the fragments from Denisova cave indicate to many the Siberian population was robust). Despite what we know was their expansive range, and the fact that they lived in eastern Eurasia for hundreds of thousands of years, to a great extent Denisovans remain genetic ghosts. They are digital shadows of their physical bodies, telling us about their relationships to other humans, details of their physiology, and immune system, but elusive in corporeal form.

The discovery of a new human on the island of Luzon, the existence of hobbits on Flores, and the diversity of Denisovans suggest that the eastern range of humanity during the Pleistocene was filled with many species of humans. The very existence of the Denisovans was window upon the vast ignorance of science in regards to the complexity of the Pleistocene world.

While Neanderthals have been the subjects of many books, they may have been a relatively homogeneous population with very precise adaptations to their northern Eurasian abode. A literal evolutionary sideshow. In contrast, Denisovans ranged from Siberia to the islands of Southeast Asia. From the edge of the tundra to the hot savanna of Sundaland.

They reflect in greater fullness the range of human experience.

Denisovans and the human story was originally published in Insitome on Medium, where people are continuing the conversation by highlighting and responding to this story.

College educated conservatives are divided on evolution

Filed under: Intelligent Design — Razib Khan @ 10:27 am


A few years ago an academic friend of mine mentioned offhand that it must be difficult for me to be an evolutionary biologist (of sorts) and a conservative (of sorts). As someone in touch with many “elite conservatives” (people who work at think-tanks and the like), that’s not true at all. Though Creationism has substantial support at the grassroots (the only time I have encountered evolution-skepticism in the last ten years has been from people who grew up fundamentalist), the reality is that at the elite levels in the conservative movement it is not a widespread position.

But, conservatives are still divided. Looking at the General Social Survey EVOLVED variable, and limiting to non-Hispanic whites, you see that while there is nearly total unanimity among self-identified liberals with college educations or higher that humans developed from animals, college-educated conservatives are split.

If you run some regressions you will see a lot of this is due not to politics, but to what politics is correlated with. Self-identified conservatives are much more likely to be religious conservatives. Those conservatives who are not religious conservatives are not very skeptical of evolution.

But one issue that I am wondering about: if most elite conservatives have no issue with evolution, and even college-educated conservatives are split down the middle, why is there so little “balance” at conservative publications? That is, periodically there is a report or opinion favorable to Intelligent Design published. But there is rarely a counter-response, even though attitudes amongst the readership are surely mixed?

I may personally attempt to change this a bit by submitting “pro-evolution” pieces here and there. We’ll see how that works out.

April 21, 2019

Indians are just as stupid as Americans

Filed under: India — Razib Khan @ 9:49 pm

You people. You people….

I specifically avoid using the term “secular” because I long ago learned what that means to Indians (just like we all know what “family values” meant in the 1990s in America).

(also, this idiot follows me on Twitter…at least as of when I posted this)

The expansion of modern humans ~50,000 as part of a regular Poisson process

Filed under: Human Evolution,Uncategorized — Razib Khan @ 4:58 pm

Last of the giants: What killed off Madagascar’s megafauna a thousand years ago?:

The first job is to understand exactly when the megafauna died out.

Radiocarbon dating of over 400 recent fossils demonstrates that animals under 22 pounds lived on Madagascar throughout the last 10,000 years. For animals over 22 pounds, there are abundant fossils up to 1,000 years ago, but relatively few since. The biggest decline in number of large animals occurred rapidly between A.D. 700 and 1000 – practically instantaneous given the long history of their existence on the island.

According to new dates on fossil bones with cut marks on them, humans arrived on Madagascar 10,500 years ago, much earlier than previously believed. But whoever these early people were, there’s no genetic evidence of them left on the island. New analysis of the human genetic diversity in modern Madagascar suggests the current population derives primarily from two waves of migration: first from Indonesia 3,000 to 2,000 years ago, and later from mainland Africa 1,500 years ago.

So it seems that people lived alongside the megafauna for thousands of years. How did the humans interact with the large animals?

Our new study found dozens of fossils with butchery marks. Cut and chop marks provide compelling evidence as to which species people were hunting and eating. Evidence of butchery of animals that are now extinct continues right up to the time of the megafaunal crash. Some people on Madagascar hunted and ate the megafauna for millennia without a population crash.

The abrupt land use change might hold some clues. The transition from a forest-dominated ecosystem to a grassland-dominated ecosystem appears to be widespread….

This research about Madagascar is important. If it turns out correct, I think it gives us deep insights about the expansion of modern humans outside of Africa ~50,000 years ago, and why their arrival resulted in the extinction of so many other human lineages. A generation ago we might have posited that some massive bio-behavioral change is what triggered this, but I am coming closer to the idea that cultural changes are punctuated enough that that may actually explain things. The culture changes first, then genes follow the culture.

Perhaps one might posit a model with massive turnovers in the hominin lineage due to this cultural dynamic occurs periodically, as if it’s a Poisson process.

Open Thread, 04/12/2019

Filed under: Open Thread — Razib Khan @ 3:52 pm

Just a reminder for people to check in on The Insight this week. Lots of talk about Denisovans between Spencer and myself. We’ve also got a follow-up podcast scheduled with a researcher working in Denisovan genomics in a few weeks (we’re on Spotify now by the way).

Our three new hires at George Mason economics. These look good.

Sri Lanka Suicide Bombings Targeting Christians Kill Hundreds. The most likely culprits seem to be a jihadist group active in southern South Asia.

A Transient Pulse of Genetic Admixture from the Crusaders in the Near East Identified from Ancient Genome Sequences. I think the “Crusader genes” are hard to find in the Near East because the collapse of the Latin kingdoms was gradual enough that “Franks” and their scions mostly managed to get out and go back to Western Europe.

Whole-genome reference panel of 1,781 Northeast Asians improves imputation accuracy of rare and low-frequency variants.

Anxious Times In Pakistan’s Pagan Valley.

Why One-Third Of Biologists Now Question Darwinism. I’m writing a response to this piece for The Federalist. Rather than a response to Intelligent Design, I want to represent what evolutionary biology really is.

Evidence for Early European Neolithic Dog Dispersal: New Data on South-Eastern European subfossil dogs from Prehistory and Antiquity Ages.

April 20, 2019

Easter Attacks in Sri Lanka

Filed under: Politics,Sri Lanka — Razib Khan @ 11:29 pm

Sri Lanka blasts: At least 137 dead and more than 150 injured in multiple church and hotel explosions:

More than 137 people have been killed and more than 150 injured after coordinated bomb blasts hit a number of high-end hotels and churches in Sri Lanka on Sunday.

The blasts, reported to have occurred in the cities of Negombo, Batticalo and the capital Colombo, targeted at least three hotels and three churches as worshippers attended Easter services.

Bodies of the dead have been received at Colombo National Hospital, according to hospital sources. Most of those injured were also taken there, hospital officials said.

Please post updates in the comments.

Gene Wolfe, death of a master

Filed under: Gene Wolfe,science fiction — Razib Khan @ 7:19 pm

Gene Wolfe, Acclaimed Science Fiction Writer, Dies at 87. Wolfe’s prose could be challenging to read. I actually read The Book of the New Sun trilogy twice because of some elements of impenetrability in the style, though there’s a reason Wolfe was acclaimed. In general, I’m not a fan of “science fantasy” or the “dying Earth” genre, but Wolfe really made it work.

One thing about Wolfe that is of interest is that like J. R. R. Tolkien he was a Catholic convert, whose religion influenced his work. Arguably more directly and consciously in the case of Wolfe. But it is subtle enough that it doesn’t distract or warrant notice. In fact, I’d argue that Severian is much less clearly a Jesus-figure than Paul in the Dune series to the naive reader.

I’m not someone who minds authors telegraphing their viewpoints and ideologies into narratives, no matter what it is. But I think there’s no point in putting it into “speculative fiction” if it’s too direct. For example, I think one reason C. S. Lewis’ Narnia cycle is less popular than Tolkien’s work is that it reads as Christian fantasy, rather than fantasy with inflections from the author’s Christian viewpoint.

Wolfe, like Tolkien, had strong personal views. But he did not let them saturate his stories. The Christian outlines and themes in The Book of the New Sun are clear after someone points them out. But they aren’t salient at all when you are reading it without foreknowledge.

April 19, 2019

Open Thread – Brown Pundits

Filed under: Open Thread — Razib Khan @ 11:27 pm

Please keep the other posts on topic. Use this for talking about whatever you want to talk about.

Let the genomic die fly!

Filed under: Human Genetics,Polygenic Risk Score — Razib Khan @ 11:19 pm


A new “polygenic risk score” (PRS) paper is making some waves, Polygenic Prediction of Weight and Obesity Trajectories from Birth to Adulthood. Since it is open access I suggest you read it.

But basically, they took ~2 million common variants (there are about ~100 million common variants in the world population) in ~300,000 individuals in 4 cohorts, and used it to predict weight. A genome-wide polygenic score statistic. The correlation with BMI of the score is 0.29. This is pretty modest. But it seems to me that the biggest and most important finding is that it seems to capture a lot of the people at the tails of the distribution.

I’m becoming more and more convinced that the best things these PRS scores can do in the near-term is to identify people who are possibly at these tails. In a complex trait context, the tails are where for diseases a lot of the people who are going to have issues later in life exist. People with BMI in the range 25-30 may have a modest increase in risks, but someone who is very obese, with BMI above 35, is at much greater risk. Over 40% of the people in the top decile here were obese. Only 10% of people in the bottom decile were.

This research comes out of the context of earlier work on the heritability of BMI. It’s around 0.75 or so. That means it runs in families. Combined with the fact that in the recent past, or in other nations, there is a great variation in median size and distribution, one can intuit that genetic dispositions and environmental context both help explain the variation we see around us. The modern American environment is clearly obesogenic. When most of the American population were involved in physical jobs on farms the environmental context was very different.

Over the next few years, there risk scores for BMI will get better, and expand to other populations. One thing that some people are pointing out is that we know it’s heritable, so why not just look at your family? As many of you know, Mendelian segregation means that siblings may have quite different risk profiles on the genomic level. Polygenic risk score prediction is I think going to be extremely interesting and informative in the case of traits which are known to be found within families across generations (e.g., autism), but don’t seem to impact everyone. Perhaps we’ll find for a given characteristic expression is random, due to some life event or cofactor such as infection. Or perhaps we’ll find that differences among siblings have some genetic basis in variants inherited from parents?

Addendum: One of the authors, Sek Kathiresan, has been answering questions on Twitter.

From basket-case to garment superpower

Filed under: Bangladesh — Razib Khan @ 10:30 pm

This article seems to use Bangladesh as a prop to beat Pakistan’s governing class over the head, Beg, borrow, repeat: Pakistan’s IMF addiction continues even as its finance minister leaves. It’s a pretty strange thing in 2019. In the 20th-century Bangladesh was known for the early 1970s famine, as well as periodic catastrophic floods.

A minimal amount of research will show that it’s not all roses in Bangladesh. There are huge governance issues, overreliance on textiles is probably not a good long-term optimum, and human capital accumulation may not keep up with the shifts toward a high-technology 21st-century economy (most of the world’s population will have to face this though).

So here is the weird thing I want to note: this blog gets about 10x more traffic from Pakistan than Bangladesh. And, it gets 100x more traffic from India than Bangladesh. This blog gets more readers from Singapore than Bangladesh!

The teleos of modern humans

Filed under: Denisovans,Human Evolution — Razib Khan @ 3:15 pm
Credit: Luke Jostins

Next week’s episode of The Insight is going to be on Denisovans. It’s a long one because so much has come out in the last few months on the specific topic, as well as the broader framing issues (e.g., the discovery of a new human species on Luzon).

One of the major points Spencer and I discussed is how important it is to understand general trends in the hominin lineage, that is, humans, before the great expansion ~60,000 years ago. For example, Neanderthals and Denisovans were very different in their paleoecology and biogeography. Neanderthals seem relatively homogeneous (probably due to repeated mass die-offs). In contrast, the “Denisovans” look to have been very deeply diverged within their clade. If the latest work is correct, and some Denisovan lineages split more than 400,000 years ago and persisted down to >100,000 years ago, then the differences between Denisovans may have been considerably greater than between any modern human lineages. For example, the Khoisan diverged from all other humans ~200,000 years ago, and there are possible deeper lineages, but not that much deeper.

Right now what you know about the Denisovans are from genomes in the Altai region. Imagine if we extrapolated to all modern humans from Altaians? It seems entirely likely that the Denisovan lineage was very diverse because it occupied very diverse territory geographically.

But diversity aside, one of the things I like to point out to people, is that there was an overall trend of encephalization among hominins. Neanderthal brains were growing larger too. We need to understand the natural history of all human lineages to understand what happened 60,000 years ago. I am coming to the conclusion that it wasn’t some incredible miracle of a behavioral big bang, but the inevitable outcome of systemic forces in hairless ape evolution that started ~2 million years ago.

The teleos of modern humans

Filed under: Denisovans,Human Evolution — Razib Khan @ 3:15 pm
Credit: Luke Jostins

Next week’s episode of The Insight is going to be on Denisovans. It’s a long one because so much has come out in the last few months on the specific topic, as well as the broader framing issues (e.g., the discovery of a new human species on Luzon).

One of the major points Spencer and I discussed is how important it is to understand general trends in the hominin lineage, that is, humans, before the great expansion ~60,000 years ago. For example, Neanderthals and Denisovans were very different in their paleoecology and biogeography. Neanderthals seem relatively homogeneous (probably due to repeated mass die-offs). In contrast, the “Denisovans” look to have been very deeply diverged within their clade. If the latest work is correct, and some Denisovan lineages split more than 400,000 years ago and persisted down to >100,000 years ago, then the differences between Denisovans may have been considerably greater than between any modern human lineages. For example, the Khoisan diverged from all other humans ~200,000 years ago, and there are possible deeper lineages, but not that much deeper.

Right now what you know about the Denisovans are from genomes in the Altai region. Imagine if we extrapolated to all modern humans from Altaians? It seems entirely likely that the Denisovan lineage was very diverse because it occupied very diverse territory geographically.

But diversity aside, one of the things I like to point out to people, is that there was an overall trend of encephalization among hominins. Neanderthal brains were growing larger too. We need to understand the natural history of all human lineages to understand what happened 60,000 years ago. I am coming to the conclusion that it wasn’t some incredible miracle of a behavioral big bang, but the inevitable outcome of systemic forces in hairless ape evolution that started ~2 million years ago.

April 17, 2019

The Insight Show Notes — Season 2, Episode 23: The Ape That Understood The Universe

Filed under: Psychology — Razib Khan @ 2:23 pm

The Insight Show Notes — Season 2, Episode 23: The Ape That Understood The Universe

This week on The Insight (Apple Podcasts, Spotify, Stitcher and Google Podcasts) we discuss the “evolutionary psychology” with Steve Stewart-Williams. The author of The Ape That Understood the Universe, Steve Stewart-Williams is interested in sex differences and the origins of cooperation.

Stewart-Williams first discussed what evolutionary psychology is. He points out that evolutionary biology doesn’t stop at the neck, and that our minds are also organs which are affected by adaptation.

There was also discussion about differences within the field and the role of Leda Cosmides and John Toobey in formulating the dominant framework. In particular, Stewart-Wiliams notes that he is not attached to particular premises associated with evolutionary psychology, such as distinct cognitive modules.

We discussed sex differences in size, and whether humans are monogamous or polygamous, and how it might relate to the behaviors of our ape relatives.

Much of the later discussion was given over to how humans develop altruism. Inclusive fitness, reciprocal altruism, and group selection were all mentioned.

Finally, we addressed the possibility that humans, the “ape that understood the universe,” might actually be something special in an evolutionary context.


The Insight Show Notes — Season 2, Episode 23: The Ape That Understood The Universe was originally published in Insitome on Medium, where people are continuing the conversation by highlighting and responding to this story.

April 16, 2019

Bring the Kalash to Ladakh!

Filed under: Culture — Razib Khan @ 9:16 am


This was something that was suggested on Twitter (or emerged out of a discussion on Twitter): why can’t the Kalash have the option of relocating to Ladakh? It’s not that different of an ecosystem, and there would be less cultural pressure to change and/or threat of assimilation.

The Indian government imposes a no-contact policy for the Sentinelese for the sake of their cultural and biological integrity (they would probably die of disease). I’m not proposing this for the Kalash, but at least bringing them to Ladakh would prevent the imminent threat of assimilation, though the individual appeal of Delhi would still be there.

There’s a lot of anger from Hindu nationalists online. Often toward Muslims. I get the reasons. But this is something that is constructive and positive. The Kalash are not a fossil race. But they preserve something that is unique and soon to be lost to the world.

April 15, 2019

Jon Snow and Daenerys Targaryen are genetically similar to full-siblings or mother and son

Filed under: Game of Thrones,Genetics — Razib Khan @ 10:37 pm

I’ve posted on this before. So I will post again just to reiterate something: in terms of genes, Jon Snow and Daenerys Targaryen are much closer to being full-siblings than they are to being aunt and nephew.

You get different numbers depending on how deeply you look at the pedigree of the two. But their relatedness is probably above 40% and below 50%. Others have confirmed:

The verbal reason without math and genealogies is simple: Daenerys Targaryen comes from an inbred lineage, and more importantly, two generations of brother-sister marriages. This means that Daenerys Targaryen and Rhaegar Targaryen were genetically much more similar than typical full-siblings. Because of this, Jon Snow and Daenerys Targaryen are much more genetically similar than typical aunts and nephews, because Jon Snow’s father was to a first approximation genetically a male and older version of Daenerys Targaryen.

An evolved mind

Filed under: Evolution,Evolutionary Psychology,Psychology — Razib Khan @ 8:40 pm

Imagine a human. We are a terrestrial, bipedal, and hairless mammal. This is very atypical in comparison to our relatives the apes and monkeys. These physical differences present us with a question: why?

Why do humans lack the fur that is generally common in our lineage? And why is our stance upright, and our locomotion bipedal? This is very rare for mammals, as is made clear by the fact that back pain is common in our species. Anatomists can tell that our spine was clearly retrofitted for bipedal locomotion.

Humans as the thinking ape

An analysis of our physical nature, our external morphology, has resulted in a great deal of evolutionary theorizing. Perhaps we are bipedal because it was an adaptation to a savanna lifestyle? By being upright we could see predators from afar, and also reduce the surface area exposed to the sun, aiding in thermoregulation. The loss of fur, body hair, may also have been an adaptation to the heat, and also had the effect of reducing our parasite load. Fur is an excellent habitat for small insects (as anyone who has watched chimpanzees spend hours grooming each other can attest!).

But evolution does not just stop at the neck. It is not simply something that shapes our bodies. It also shapes our internal physiology. And, our psychology. Our minds.
Humans have big brains!

One of the most distinctive aspects of human biology is that our brains are relatively large for our body size. Large mammals tend to have smaller brains proportionally. And yet we are a large mammal that still has a large brain. Even our species name alludes to our brain implicitly. Homo sapiens means “wise man” in Latin. No one can accuse our species of low self-regard!

More interestingly, humans are a big-brained species in a relatively big-brained lineage, the primates. Though the human brain only accounts for ~2% of our species’ body weight, it accounts for ~20% of the caloric expenditure of a resting human.

The brain is an energetically expensive biological machine that is fueled by sugar.

Evolutionarily speaking, the last two million years have seen an overall increase in the size of the brain amongst hominins. The cranial capacity of Homo erectus was about 1000 cubic centimeters. Modern humans are around 1300 cubic centimeters (though the largest known cranial capacity belonged to Neanderthals).

Such peculiarities of long-term change in size across a group of related species is strongly suggestive of directional selection, and therefore adaptation.

These facts are not just fascinating to evolutionary biologists. They have resulted in the emergence of a field within psychology which takes seriously the proposition that the human mind itself is a set of adaptations.

These scholars believe that mental and behavioral characteristics can be analyzed through inspection of function, and considerations of the evolutionary dynamics which shape change over time.

As noted above, the human brain is incredibly metabolically expensive. And, over the past two million years in the lineage of Homo the cranial capacity has increased in a systematic manner. From an evolutionary perspective, it seems unlikely that a very expensive organ would continue to get more expensive simply due to random genetic drift or as a side effect of other processes.

If not chance, then what? One force which drives change in evolution is natural selection, which results in adaptations to the environment in populations. Psychologists who are curious about how the mind can inform our evolutionary history through adaptations, and also how evolutionary history can inform our understanding of the mind and behavior, are called “evolutionary psychologists.”

E. O. Wilson, intellectual and cultural revolutionary

The emergence of this field is to a great extent an illustration of cultural evolution within science. Throughout much of the 20th-century psychologists spent little time reflecting upon evolution, let alone exploring the hereditary basis of cognition. Neither Freudianism nor Behaviorism put much stock in evolutionary biology. Both believed that the causes of human variation and similarity were due to variation and similarity of experience.

But in the 1970s this stance began to change. First, psychologists themselves were realizing that the human mind was not a “blank slate,” a simple general tool which took in environmental inputs to generate behavioral outputs. Rather, the mind seemed to have some hard-wired features. For example, humans are able to recognize the faces of people we know immediately, without having to “think” about it (today we know that a small minority of humans cannot do this and that this is a genetic characteristic which runs through families). We have strong predispositions and core competencies which we are born with. It’s not all environment.

If that is true, then biology has to step in. And as Theodosius Dobzhansky stated, “Nothing in biology makes sense except in the light of evolution.”

The second thing that happened in the 1970s is that the entomologist E. O. Wilson became a public intellectual with the publication of Sociobiology: The New Synthesis. Though most of Wilson’s work has been on ants, he made a call to revive an exploration of human nature through the principles of biology, and in particular evolutionary science. Though “sociobiology” is often used to understand “animal societies”, such as ants, its most controversial application was to human societies, as Wilson was arguing for.

The idea of studying humans as Wilson had studied ants triggered a cultural war within academia. This is documented in Ullica Segerstrale’s Defenders of the Truth: The Sociobiology Debate (the denouement of this period was the physical assault of E. O. Wilson at a scientific conference). It was out of this tumultuous context that a pair of psychologists based out of the University of California in Santa Barbara, Leda Cosmides and John Tooby, developed the framework of modern evolutionary psychology. Abandoning sociobiology’s grandest ambition of absorbing the study of human behavior as simply a branch of biology, Tooby and Cosmides outlined a framework focused on features of the mind, and how they may have emerged as adaptations to selection pressures, and how our evolutionary past redounds to contemporary behaviors. The “Pleistocene mind” was born.

The metabolically expensive brain was not a single thing in Tooby and Cosmides’s framework. Rather, the brain is a large organ which bundles together many functions. It’s a multi-use tool, with specialized pre-installed functions. Or, in the metaphor of many evolutionary psychologists, a “swiss army knife.”

One of the key topics of evolutionary psychology was the question that E. O. Wilson was originally interested in: why are humans altruistic? That is, why do humans help other people when it does not always seem in their natural interest to do so?

Ultimately, this leads to addressing how humans form societies of massive scale, like ants and termites. To answer this question one can look at it from two ends, that of evolutionary biology, and that of cognitive neuroscience and psychology. Evolution provides theoretical frameworks, while it is on the level of neuroscience and psychology that functional adaptations occur. Evolution generates the historical inputs of the past, while the brain and behavior are the outputs of the present.

To understand altruism in nature evolutionary biologists make recourse to a range of theories. One of the primary ones is “inclusive fitness,” developed in the 1960s by W. D. Hamilton, John Maynard Smith, and George Price. The descriptive logic is simple: you help people near to you because they are likely related to you, and so they share your genes. When you help someone who shares your genes, your genes are “helping themselves.” The altruism in this model is actually genetically self-interested and evolves naturally because genes exist to propagate themselves.

This evolutionary framework explains a host of cross-cultural behaviors and sentiments.

Across human societies, the connection between a mother and her offspring is arguably the most intense of any between pairs of humans. As it happens, this is the relationship which is both genetically the closest, along with that between siblings and father to offspring, and, the most certain. A mother knows whether a child is adopted or her biological child with certainty. Depending on the cultural context there is less certainty of fatherhood (and therefore, a full-sibling relationship). Even full-siblings vary across the 50% range due to Mendelian segregation.

By helping their children, mothers are fostering the persistence of their own genes into the future.
The amygdala

Though inclusive fitness on a theoretical biological level can be outlined and understood as a complex set of equations and mathematical relationships, on the scale of humans it manifests as features and connections in the brain, and a suite of recurrent behaviors and emotions. Many of the emotions which are essential to attachment, as well as fear and love, are localized to the region of the brain around the amygdala. The broader limbic system is common to mammals and may reflect the social complexity of the mammalian lineage in comparison to their reptilian ancestors.

Social systems have changed over time due to selection pressures in the environment, driving changes in the brains of whole lineages.

In terms of human societies, the adaptation for altruism is exhibited in both individual psychological characteristics and, cultural characteristics. Unlike some organisms, human mothers do not naively imprint upon their offspring but develop a connection through a conscious understanding of the relationship. Humans have the ability to recognize faces, and also detect genetic similarity through intuitive folk biologies of heredity. Parents and offspring resemble each other. Facial recognition is clearly a hard-wired adaptation, but folk biological intuitions also seem relatively universal, suggesting some mental faculties which are derived from adaptation in our understanding of inheritance.

Human childhoods are extremely long, and the connection between parent and offspring is the most important axis of affinity in our species. But it is not the only connection. Paleolithic humans seem to have lived in small bands, similar to hunter-gatherers today. These bands consisted of related and unrelated individuals. The relatedness among many individuals within the bands likely increased social cohesion and allowed for an explanation for why individuals might cooperate in high risk but high reward behavior, such as hunting big game.

Even if there was a risk of death, if individuals were related to others in the band, assuming a long-term payoff in risky hunting, the behavior was evolutionarily favored.

Though there are many cultural scripts revolving around kinship, whether factual or fictive, some of the behaviors may have innate psychological roots. The “Westermarck effect” refers to the tendency for individuals who were raised together to exhibit decreased sexual attraction to each other. Though foster-siblings may not have a genetic relationship, their nearby development and maturation seem to trigger the same psychological reflexes as biological siblings, which is rational in light of the fact that historically the vast majority of young people one would be raised up in close proximity to were biological siblings.

The genetic consequences of inbreeding are well known to geneticists and reflect some level of folk wisdom, but the Westermarck effect tells us that it had an evolutionary impact, reshaping human psychology to reduce the likelihood of sexual relationships with close relatives.

The intersection of evolution and psychology is a vast space, filled with controversies and possibilities.

Over the last generation, evolutionary psychology has been a lightning rod for scientific debate, and cultural tumult. Part of this was due to the way the field developed in the 1980s, as it was associated with a narrow set of researchers at a few institutions with very strong opinions on many theoretical and practical topics. But over the past few decades, a broader set of scholars have explored the evolutionary basis of human nature, utilizing the toolkit of evolutionary biology to understand our psychology, and so furthering an understanding of the evolutionary basis of human nature.


An evolved mind was originally published in Insitome on Medium, where people are continuing the conversation by highlighting and responding to this story.

The end of the Kalash is nigh

Filed under: Open Thread — Razib Khan @ 6:32 pm

Verily I say unto you, this generation shall not pass, till all the Kafir Kalash bend the knee to the one true God!

I think anyone who has given it any thought knew that this was inevitable and just a matter of time. That time seems to be now. The Kalash compensated for conversion with higher endogenous fertility, but if it is true that educated young women are converting to Islam, their ability to reproduce their numbers will decrease rapidly.

Anxious Times In Pakistan’s Pagan Valley Rising Islamic Influence Pressures An Ancient People:

Naveed is a member of the Kalash, a pagan community known for their fair skin that has long inhabited this area near the border with Afghanistan. The Kalash people, many of whom believe they are the descendants of the armies of Alexander the Great, have held on to their religious beliefs and colorful rituals for centuries, even as a sea of Islam has encircled them.

But the unique traditions of the Kalash are coming under mounting cultural pressure as the pace of conversions to Islam accelerates within Pakistan’s smallest ethnoreligious community. The Kalash population currently numbers between 3,000-4,000, and locals estimate that some 300 of their members have converted to Islam over the past three years, The Washington Post reported in November. Some local reports, however, have said the figure is not that high.

First, to preempt genetic comments: the Kalash do not descend from Europeans like Alexander’s Macedonians, as such. Rather, they are a mix of Indo-Aryan steppe ancestry, with a base of Iranian farmer (the largest component probably), along with a residual but non-trivial amount of indigenous deep South Asia ancestry (AASI in other posts). It is probably fair to say that they are among the most Indo-Aryan peoples in the Indian subcontinent, but the recent work on the Ror people indicates that some Jatt groups are similar.

Second, the fact that they are not Muslim to this day is simply due to the contingencies of history. The Afghan conquest of nearby Nuristan in the last decade of the 19th century resulted in the wholesale conversion of the pagans of that region. The fact that the Kafir Kalash were on the British side of the border meant that they were spared forced conversion.

And so almost magically deep into the 21st century, we got a window into the world of Indo-European customs and practices of the descendants of the Andronovo and Sintashta cultures, relatively isolated from the primary stream of what became Hinduism to the south and east and Zoroastrianism to the west (both of which interacted with non-Indo-European indigenous elements). The sun is setting on these people, whether through forced conversion, or the attractiveness of modernization and assimilation into the dominant culture of Pakistan.

In a few generations, they will be but faint memories to their descendants, and a single thread of the many threads of human cultural history will vanish forever.

The end of the Kalash is nigh

Filed under: Open Thread — Razib Khan @ 6:32 pm

Verily I say unto you, this generation shall not pass, till all the Kafir Kalash bend the knee to the one true God!

I think anyone who has given it any thought knew that this was inevitable and just a matter of time. That time seems to be now. The Kalash compensated for conversion with higher endogenous fertility, but if it is true that educated young women are converting to Islam, their ability to reproduce their numbers will decrease rapidly.

Anxious Times In Pakistan’s Pagan Valley Rising Islamic Influence Pressures An Ancient People:

Naveed is a member of the Kalash, a pagan community known for their fair skin that has long inhabited this area near the border with Afghanistan. The Kalash people, many of whom believe they are the descendants of the armies of Alexander the Great, have held on to their religious beliefs and colorful rituals for centuries, even as a sea of Islam has encircled them.

But the unique traditions of the Kalash are coming under mounting cultural pressure as the pace of conversions to Islam accelerates within Pakistan’s smallest ethnoreligious community. The Kalash population currently numbers between 3,000-4,000, and locals estimate that some 300 of their members have converted to Islam over the past three years, The Washington Post reported in November. Some local reports, however, have said the figure is not that high.

First, to preempt genetic comments: the Kalash do not descend from Europeans like Alexander’s Macedonians, as such. Rather, they are a mix of Indo-Aryan steppe ancestry, with a base of Iranian farmer (the largest component probably), along with a residual but non-trivial amount of indigenous deep South Asia ancestry (AASI in other posts). It is probably fair to say that they are among the most Indo-Aryan peoples in the Indian subcontinent, but the recent work on the Ror people indicates that some Jatt groups are similar.

Second, the fact that they are not Muslim to this day is simply due to the contingencies of history. The Afghan conquest of nearby Nuristan in the last decade of the 19th century resulted in the wholesale conversion of the pagans of that region. The fact that the Kafir Kalash were on the British side of the border meant that they were spared forced conversion.

And so almost magically deep into the 21st century, we got a window into the world of Indo-European customs and practices of the descendants of the Andronovo and Sintashta cultures, relatively isolated from the primary stream of what became Hinduism to the south and east and Zoroastrianism to the west (both of which interacted with non-Indo-European indigenous elements). The sun is setting on these people, whether through forced conversion, or the attractiveness of modernization and assimilation into the dominant culture of Pakistan.

In a few generations, they will be but faint memories to their descendants, and a single thread of the many threads of human cultural history will vanish forever.

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