In the survey below I asked if you knew about how many migrants per generation were needed to prevent divergence between populations. About ~80 percent of you stated you did not know the answer. That was not totally surprising to me. The reason I asked is that the result is moderately obscure, but also rather surprisingly simple and fruitful. The rule of thumb is that 1 migrant per generation is needed to prevent divergence.*
It doesn’t tell you much in and of itself of course. But if you think about it you can inject that fact into all sorts of other population genetic phenomena. For example, to have selection across two populations which is not reducible to selection within those populations (i.e., inter-demic selection) you need group-level genetic differences. These differences can be measured by the Fst statistic. In short the value of Fst tells you the proportion of variation which can be attributed to between-group differences (e.g., Fst across human races is ~0.15). For natural selection to have any adaptive effect you also need heritable variation. If you have lots of heritable variation selection can be weaker, while if you have little heritable variation selection has to be very strong (see response to selection). Fst is a rough gauge of heritable variation when you are evaluating group level differences. An Fst of 1.0 would imply that the groups are nearly perfectly distinct at the loci of interest, while an Fst of 0.0 would imply that the groups are not genetically distinct at all. With no distinction selection would have no efficacy in terms of driving adaptation. All this is a long way to saying that the 1 migrant rule is one reason that evolutionary biologists take a skeptical position in relation to group selection. It tends to quickly erase the variation which group selection depends upon.
The study focuses on the Hadza, a hunter-gatherer population of Tanzania. Their language seems to be an isolate, though there have been suggestions of a connection to Khoisan. Additionally the genetic evidences tells us that like the Bushmen and Pygmies the Hadza do descend from populations which are basal to other human lineages, and were likely resident in their homeland before the arrival of farmers. And it is critical to also note that the Hadza are probably uninterrupted hunter-gatherers in terms of the history of their lifestyle, as agriculture likely arrived in Tanzania on the order of two thousand years ago, and their genetic distinctiveness indicates a separation from groups like Bantus far deeper in time. When it comes to Paleolithic model populations the Hadza are relatively “uncontaminated.”
The post below on teachers elicited some strange responses. Its ultimate aim was to show that teachers are not as dull as the average education major may imply to you. Instead many people were highly offended at the idea that physical education teachers may not be the sharpest tools in the shed due to their weak standardized test scores. On average. It turns out that the idea of average, and the reality of variation, is so novel that unless you elaborate in exquisite detail all the common sense qualifications, people feel the need to emphasize exceptions to the rule. For example, over at Fark:
Apparently what had happened was this: He played college football. He majored in math, minored in education. When he went to go get a job, he took it as a math teacher. When the football coach retired/quit, he took over. When funding for an advance computer class was offered, he said he could teach it after he got the certs – he easily got them within a month.
So the anecdote here is a math teacher who also coached. Obviously the primary issue happens to be physical education teachers who become math teachers! (it happened to me, and it happened to other readers apparently) In the course of double checking the previous post I found some more interesting GRE numbers. You remember the post where I analyzed and reported on GRE scores by intended graduate school concentration? It was a very popular post (for example, philosophy departments like it because it highlights that people who want to study philosophy have very strong GRE scores).
As it happens the table which I reported on is relatively coarse. ETS has a much more fine-grained set of results. Want to know how aspiring geneticists stack up against aspiring ecologists? Look no further! There are a lot of disciplines. I wanted to focus on the ones of interest to me, and I limited them to cases where the N was 100 or greater (though many of these have N’s in the thousands).
The excellent site io9 has a piece up today which is a fascinating indicator of the nature of popular science publications as a lagging indicator. It is a re-post of a piece published last April, How Mitochondrial Eve connected all humanity and rewrote human evolution. In it you have an encapsulation of a particular period in our understanding of human natural history through evolutionary genetics. Notice for example the focus on maternally transmitted lineages, mtDNA and Y chromosomes. And the citations on genealogy date to the middle aughts. The science is mostly correct as far as it goes in the details (or at least it is defensible, last I checked there was still debate as to the validity of the molecular clocks used for Y chromosomal lineages), but it misses the big picture of how we’ve reframed our understanding of the human past over the last few years. The distance between 2011 and 2009 is far greater in this sense than between 2009 and 1999 (or even 2009 and 1989!). The io9 piece is a reflection of the era before the paradigmatic rupture.
A regular issue that comes up on this weblog is that many of my posts are difficult to understand. I am aware of this. Unfortunately a problem is that there is a wide variation in fluency in genetics knowledge among the readership. To get a better sense I have created a survey with 60+ questions. It may seem like a lot, but the questions go fast because there are only three answers to each, and you should immediately know how to respond. I will likely use these responses to guide me in future “refresher” posts and the like. The questions range from relatively simple to moderately abstruse. That’s by design. Thanks.
Note: The survey will not show up in the RSS, so please click through!
Several companies provide tests that can confirm whether adoptees are related to individuals they already know. Others cast a wider net by plugging DNA results into databases that contain tens of thousands of genetic samples, provided mostly by people searching for their ancestral roots. The tests detect genetic markers that reveal whether people share a common ancestor or relative.
Some experts on adoption and genetics have criticized ancestry and genealogy testing companies, saying they are, at times, connecting people whose genetic links are tenuous — in effect stretching the definition of a relative. Nevertheless, the growing popularity of the tests, combined with social media sites that connect people day to day, has given some adoptees a sense of family that feels tangible, intimate and immediate.
You may not have noticed, but Google has been spiffing up its Data Explorer. Poking around you see nice illustrations of phenomena which you otherwise may just read about. For example, Argentina has been one of the classic illustrations in economic history of stagnation. To a great extent it peaked around 1900, and development has been erratic since then. This is clear when you see how much its neighbors and other Latin American nations have caught up:
Apparently the national media is reporting that scientific genealogy may result in leads to a cold case. The principle is simple: apparently Y chromosomal material was matched to public genealogy databases. From this the researcher concluded that the perpetrator is probably a male line descendant of Robert Fuller of Salem, Massachusetts. Contrary to the urban legends it does not seem that false paternity rates are much higher than ~1 percent in many societies (for example).
CeCe Moore and Blaine Bettinger have covered this story in detail, so I won’t go much further in this specific case. But as more and more people get typed and sequenced I suspect that genetic material is going to be more and more “actionable.” What long term effects will this have? Will criminals start taking precautions?
I haven’t posted one of these in a long time. My own assumption is that I know the core readership of this weblog through various means relating to comments (many of you connect your email addresses to Facebook, and usually I can do an IP trace if that’s not feasible). But I know many people do not comment, so this is an opportunity to “out” yourself and such (also, over the years there has been some talk about “networking” by readers who share common eclectic interests).
I have seen references to this around the web, and don’t really know if I can believe this, because the details are so disturbing to consider. So I’ll pass it on, You can expect threats if you discuss Sharia:
My One Law for All Co-Spokesperson Anne Marie Waters was to speak at a meeting on Sharia Law and Human Rights at the University of London last night.
It was cancelled by the Queen Mary Atheism, Secularism and Humanism Society organisers after police had to be called in due to Islamist threats. One Islamist filmed everyone at the meeting and announced he would hunt down those who said anything negative about Islam’s prophet. Outside the hall, he threatened to kill anyone who defamed the prophet. Reference was made to the Jesus and Mo cartoon saga at UCL.
The University’s security guard – a real gem –arrived first only to blame the speaker and organisers rather than those issuing death threats. He said: ‘If you will have these discussions, what do you expect?’ Err, to speak without being threatened with death maybe?
A crazy British Muslim threatening to kill someone for defaming the prophet isn’t too surprising. ~3 percent of British Muslim university students think apostates should be killed. What is disturbing is that the establishment institutions are accepting this sort of disproportionate response as normal behavior. As in centuries past it is now the atheists who are by their nature offensive, and disturbing public order.
In the Netherlands the Dutch Muslim Party is going to contest for parliament. It already has some purchase in major cities with large Muslim minorities. Naturally one of its planks is to prosecute those who give offense to religion and religious people. Just jump to article 2.2. Welcome to multiculturalism!
In an exchange with Mark Shriver, I was pointed to this 2007 position paper in Science, The Science and Business of Genetic Ancestry Testing. It’s an interesting historical artifact. Much of the critique was aimed at AncestrybyDNA, but it can be generalized. Now that 23andMe has ~100,000 customers, have the things which they worried about come to be? Perhaps one of the more curious aspects of all this is that individuals no longer need to rely exclusively on the commercial gatekeepers if they have their raw genotype.
I can accept some bioethical concerns about the implications of genetics. For example, if people use odds ratios too promiscuously in PGD. But the whole handwringing about the implications of a crisper genomic understanding of one’s ancestry seems to me to be a clear case of intellectual stakeholders worried about democraticization. In other words, scholars whose bread & butter is “race matters” are not particularly excited by the prospect of their study subjects shifting from passive acceptance of the taxonomies which are imposed from the outside, to constructing their own identities from novel information.
I have blogged about the genetics of altitudeadaptation before. There seem to be three populations in the world which have been subject to very strong natural selection, resulting in physiological differences, in response to the human tendency toward hypoxia. Two of them are relatively well known, the Tibetans and the indigenous people of the Andes. But the highlanders of Ethiopia have been less well studied, nor have they received as much attention. But the capital of Ethiopia, Addis Ababa, is nearly 8,000 feet above sea level!
Another interesting aspect to this phenomenon is that it looks like the three populations respond to adaptive pressures differently. Their physiological response varies. And the more recent work in genomics implies that though there are similarities between the Asian and American populations, there are also differences. This illustrates the evolutionary principle of convergence, where different populations approach the same phenotypic optimum, though by somewhat different means. To my knowledge there has not been as much investigation of the African example. Until now. A new provisional paper in Genome Biology is out, Genetic adaptation to high altitude in the Ethiopian highlands:
Update: If interested, please email me at contactgnxp -at- gmail -dot- com. Also, I am getting some feedback via 23andMe that people with white South African matches noticed Africa segments in many of the ancestry paintings. This has definitely increased by probability that the admixture proportion is ~5 percent. There will probably be a few genotypes coming in shortly, but I am going to see if I can get more people typed (fundraising appeal pending!).
It’s been a while since I’ve gone looking for genotypes of particular ethnic groups. The results were rather good for the Tutsi and Malagasy. So I thought I’d venture out again, despite being a bit busy. Here’s what I want: the genotype of an Afrikaner (or several). A few years ago South African geneticist J. M. Greeff did an analysis of his own pedigree, and estimated that he had ~6 percent non-European ancestry (he did validate this with some genetic markers; e.g., his father’s mtDNA is of the M haplogroup, which is almost always Indian). This is in line with other genealogists who have estimated, about 5 percent non-European heritage. How much should we trust these non-biological studies? The genomic estimates of African American ancestry being ~20 percent European were anticipated by analyses of family histories from text records, so we certainly shouldn’t dismiss them (in fact, it seems possible that these analyses will underestimate non-European ancestry because of cryptic individuals in the pedigrees).
And we have plenty of records of people of non-European ancestry contributing to the Afrikaner population in any case. Greeff found the records for his own pedigree, but the first Governor of the Dutch Cape Colony was himself of mixed-race (his mother was Eurasian). The question is is a matter of degree. Are Afrikaners like American whites, with hardly any non-European ancestry (~1 percent or less), or like Latin American whites, with significant non-European ancestry (~5 to 20 percent)? My own bet is that they’ll be in the middle. The proportion of non-European ancestry is low enough that individuals such as Sandra Laing are very rare indeed. But if the 5 percent estimate is valid, and almost of all these ancestors were women, then a larger proportion of the mtDNA is going to be non-European.
The Pith: More caveman admixture in modern humans, especially Melanesians!
A new paper on archaic adaptive introgression among Melanesians has beendiscussed elsewhere. But I think it is worth reviewing, because it’s probably a foretaste of what’s to come. Researchers are combing through the human genome, as more and more genomes come on line, in the search of weird and unexpected variation. The paper is in Molecular Biology and Evolution, and is titled Global genetic variation at OAS1 provides evidence of archaic admixture in Melanesian populations (why is it that this journal doesn’t even allow supplemental information to be free to the public?). The two primary figures from this paper do a good job of illustrating the main result.
The first figure is a phylogenetic tree of haplotypes at the OAS1 locus, with pie charts showing the proportion of individuals from a set of populations which contribute to the total number for that haplotye. So you see above that the “deep lineage” is relatively distant from a cluster of other haplotypes (as measured by mutational differences which are proportional to depth of common ancestry), and, that deep linage is exclusively found in Papuans in this set. The second figure shows the frequency of the deep lineage haplotype over a larger set of populations. I cut off the section which shows that Africans are at zero percent. The haplotype is found almost exclusively in Melanesian populations, except for the fact out of over 200 South Asians they sampled, 3 of them carried it (2 Pakistanis, 1 Sri Lankan). There is aspect though not evident in the figures above, but which is clear in the abstract that you need to know:
Apple executives say that going overseas, at this point, is their only option. One former executive described how the company relied upon a Chinese factory to revamp iPhone manufacturing just weeks before the device was due on shelves. Apple had redesigned the iPhone’s screen at the last minute, forcing an assembly line overhaul. New screens began arriving at the plant near midnight.
A foreman immediately roused 8,000 workers inside the company’s dormitories, according to the executive. Each employee was given a biscuit and a cup of tea, guided to a workstation and within half an hour started a 12-hour shift fitting glass screens into beveled frames. Within 96 hours, the plant was producing over 10,000 iPhones a day.
“The speed and flexibility is breathtaking,” the executive said. “There’s no American plant that can match that.”
The story emphasizes that labor costs are not the primary issue here. There is the natural discussion of skill levels, and the sheer number of Chinese works coming online. But there simply is no way that Foxconn City could exist in the United States today. There is no way I can deny the massive quality of life improvements in China over the past generation. But, the flip side of this is that a way of life has now emerged organically in places like Shenzen which is rather reminiscent of late 19th and early 20th century dystopian visions of the industrial future.
Razib Khan’s degrees are in biochemistry and biology. He has blogged about genetics since 2002, previously worked in software development, is an Unz Foundation Junior Fellow and lives in the western US. He loves habaneros.
In the survey below I asked if you knew about how many migrants per generation were needed to prevent divergence between populations. About ~80 percent of you stated you did not know the answer. That was not totally surprising to me. The reason I asked is that the result is moderately obscure, but also rather surprisingly simple and fruitful. The rule of thumb is that 1 migrant per generation is needed to prevent divergence.*
Razib Khan’s degrees are in biochemistry and biology. He has blogged about genetics since 2002, previously worked in software development, is an Unz Foundation Junior Fellow and lives in the western US. He loves habaneros.
