Razib Khan One-stop-shopping for all of my content

October 30, 2013

The human genetic casserole

Filed under: Archaeology,Human History — Razib Khan @ 6:48 pm

HotdishI haven’t said much about this article in Science, Ancient DNA Links Native Americans With Europe, because it would be an understatement to say I’m digesting it. I would offer up a caution that using terms like “Europeans” and “East Asians” for populations which flourished ~25,000 years ago might be misleading. We are used to thinking of genetic distance in terms of space, but time is also a dimension to consider. Populations even without admixture or gene flow will have drifted in allele frequencies over so many generations.

But I have to admit that it seems more and more likely that most extant modern populations are combinations of lineages which diverged very early after the “Out of Africa” migration. We see this clearly with South Asians, and now Europeans and Native Americans. The Reich lab has also found evidence of admixture in in Australians. The closer we look, the more amalgamation we see between disparate lineages. Using the elements of the present to reconstruct the patterns of the past is going to be a more daunting task than most would have guessed.

The post The human genetic casserole appeared first on Gene Expression.

October 27, 2013

Our forefathers were fierce & our foremothers were faithful

Filed under: Cuckoldry,Evolution — Razib Khan @ 5:51 pm

Credit: Chineeb

Credit: Chineeb

One of the peculiarities of human historical genetics is that people can simultaneously accept the existence of aggressive polygynous males such as Genghis Khan, and promiscuous females who give rise to the idea that 1 out of 10 children have an incorrect assigned paternity. I’ve mentioned the cuckoldry myth before. It is a common evolutionary myth; I’ve heard many biologists quote the 1 out of 10 number, and have often made myself obnoxious by pointing to the contradictory literature in this area. This isn’t to say that cuckoldry doesn’t exist. There’s certainly an evolutionary reason so many males engage in “mate guarding.” But you don’t need a high frequency of a trait to allow it to be selectively constrained. If it’s deleterious, then it will be driven down in frequency rather quickly. Whenever you get outbreaks of males who are sanguine about providing resources for offspring who are not their biological issue, natural selection will kick in and guarantee that this generous spirit toward their cheating partners and the delinquent cads does not persist.


The way that modern genetics adds value to this area is that one can compare Y chromosomal lineages to surnames. The logic is simple. If you have a constant frequency of misattributed paternity per generation over time the correlation between a surname and a Y chromosomal lineage will weaken. In addition, because the interlopers are likely to be different from each other you’ll have a pattern with (for example) ~50% of the male individuals of a given surname may carry one haplotype, while the other ~50% are distributed across hundreds of other haplotypes (one can imagine twists on the scenario, for example an early interloper might result in a secondary highly frequent haplotype).

So here’s an new study to bury this tired old urban myth, Low historical rates of cuckoldry in a Western European human population traced by Y-chromosome and genealogical data:

Overall, our results provide the first large-scale, unbiased genetic study of historical EPP rates in a human Western European population, with two independent estimation methods giving largely concordant results. Using the most direct estimation method, based on pairs of males that had a GCA in the last few centuries, we estimated the average EPP rate at 0.91% per generation (95% CI: lower bound 0.41% and upper bound 1.75%). This method took advantage of the hypervariability and mutability of Y-STR haplotypes, and the high phylogenetic resolution of the used Y-SNP haplogroups, which allowed paternally unrelated males to be easily recognized as such [35]. In addition, using a second method that was based on the population genetic traces of a past immigration event which happened at the end of the sixteenth century, we estimated the EPP rate at around 2%. Although this estimate had a broader CI (upper 95% confidence limit = 8%), the actual estimate was close to the first one.

Both of our methods therefore estimated a substantially lower historical EPP rate for Flanders than the 8–30% per generation suggested by previous studies based on behavioural data on rates of EPCs in Western Europe and given the absence of reliable contraceptive methods [30–33]….

It’s open access, so read the whole thing if you aren’t convinced.

The authors are clear that this is from a sample in Flanders, but I do not find that this population should be that exceptional across the Eurasian Ecumene. In other words, I’ll be willing to put down money that Indian gotras and Chinese patrlineal clans will exhibit the same pattern of cuckoldry frequency. Additionally, the authors note that this pattern of high paternity confidence is paired with male investment in offspring. That seems relatively typical among many members of our species, though the extent seems to vary by population and environmental condition.

The post Our forefathers were fierce & our foremothers were faithful appeared first on Gene Expression.

Our forefathers were fierce & our foremothers were faithful

Filed under: Cuckoldry,Evolution — Razib Khan @ 5:51 pm

Credit: Chineeb

Credit: Chineeb

One of the peculiarities of human historical genetics is that people can simultaneously accept the existence of aggressive polygynous males such as Genghis Khan, and promiscuous females who give rise to the idea that 1 out of 10 children have an incorrect assigned paternity. I’ve mentioned the cuckoldry myth before. It is a common evolutionary myth; I’ve heard many biologists quote the 1 out of 10 number, and have often made myself obnoxious by pointing to the contradictory literature in this area. This isn’t to say that cuckoldry doesn’t exist. There’s certainly an evolutionary reason so many males engage in “mate guarding.” But you don’t need a high frequency of a trait to allow it to be selectively constrained. If it’s deleterious, then it will be driven down in frequency rather quickly. Whenever you get outbreaks of males who are sanguine about providing resources for offspring who are not their biological issue, natural selection will kick in and guarantee that this generous spirit toward their cheating partners and the delinquent cads does not persist.


The way that modern genetics adds value to this area is that one can compare Y chromosomal lineages to surnames. The logic is simple. If you have a constant frequency of misattributed paternity per generation over time the correlation between a surname and a Y chromosomal lineage will weaken. In addition, because the interlopers are likely to be different from each other you’ll have a pattern with (for example) ~50% of the male individuals of a given surname may carry one haplotype, while the other ~50% are distributed across hundreds of other haplotypes (one can imagine twists on the scenario, for example an early interloper might result in a secondary highly frequent haplotype).

So here’s an new study to bury this tired old urban myth, Low historical rates of cuckoldry in a Western European human population traced by Y-chromosome and genealogical data:

Overall, our results provide the first large-scale, unbiased genetic study of historical EPP rates in a human Western European population, with two independent estimation methods giving largely concordant results. Using the most direct estimation method, based on pairs of males that had a GCA in the last few centuries, we estimated the average EPP rate at 0.91% per generation (95% CI: lower bound 0.41% and upper bound 1.75%). This method took advantage of the hypervariability and mutability of Y-STR haplotypes, and the high phylogenetic resolution of the used Y-SNP haplogroups, which allowed paternally unrelated males to be easily recognized as such [35]. In addition, using a second method that was based on the population genetic traces of a past immigration event which happened at the end of the sixteenth century, we estimated the EPP rate at around 2%. Although this estimate had a broader CI (upper 95% confidence limit = 8%), the actual estimate was close to the first one.

Both of our methods therefore estimated a substantially lower historical EPP rate for Flanders than the 8–30% per generation suggested by previous studies based on behavioural data on rates of EPCs in Western Europe and given the absence of reliable contraceptive methods [30–33]….

It’s open access, so read the whole thing if you aren’t convinced.

The authors are clear that this is from a sample in Flanders, but I do not find that this population should be that exceptional across the Eurasian Ecumene. In other words, I’ll be willing to put down money that Indian gotras and Chinese patrlineal clans will exhibit the same pattern of cuckoldry frequency. Additionally, the authors note that this pattern of high paternity confidence is paired with male investment in offspring. That seems relatively typical among many members of our species, though the extent seems to vary by population and environmental condition.

The post Our forefathers were fierce & our foremothers were faithful appeared first on Gene Expression.

Open Thread, 10/27/2013

Filed under: Culture — Razib Khan @ 2:33 am

I’ll be on the Kathleen Dunn Show on Monday, 2 to 3 PM Central Standard Time. You’ll be able to listen to the show after it airs on the website. It will be about my piece in Slate.

AJjacketI recently read Ancestral Journeys: The Peopling of Europe from the First Venturers to the Vikings by Jean Manco. You can find more information at her website, but I pretty much would recommend this book to all my non-scientist readers. I’d recommend it to many of the scientists too, if you are rather weak on archaeology, because that’s where Manco’s knowledge is really impressive. It’s not a perfect book, and I don’t agree with all the details, but it’s a very detailed, dense, and fast read.

There was a question below in regards to the Fast Company profile of 23andMe and what they’re trying to do. A major ethical issue brought up is whether it is acceptable to type children and disclose possible disease risk later on in life. As an extreme case, what if you find out that your child is going to develop a life threatening disease by the time they’re 40? My own perspective as a parent is that I’d like to know, and I’d probably want to tell my child as soon as I think they can handle it. The reason is simple: you base your life decisions on various aspects of life expectancy. People put things off, or forgo consumption, all the time.

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