Archive for the ‘Genetics’ Category

Indian-American domination of the Spelling Bee – by the numbers

May 29, 2015

The domination of the Spelling Bee by Indian-Americans continues. It resembles the domination of long distance running events by East Africans. It is highly unlikely that a genetic component is not involved.

Vanya Shivashankar of Olathe, Kansas, and Gokul Venkatachalam, St. Louis, Missouri lift the trophy after becoming co-champions after the final round of the 88th annual Scripps National Spelling Bee at National Harbour, Maryland on Thursday.

  1. Vanya Shivashankar and Gokul Venkatachalam, both 8th graders, jointly won the 88th Scripps Spelling Bee.
  2. Vanya is the first sibling of a past champion to win, with her sister, Kavya, winning in 2009.
  3. 285 spellers took part in the 88th US Scripps Spelling Bee competition.
  4. They came from the 50 U.S. states, American Samoa, Guam, Puerto Rico, the U.S. Virgin Islands, and Department of Defense Schools in Europe, the Bahamas, Canada, China, Ghana, Jamaica, Japan and South Korea.
  5. Though Indian-Americans make up just 1% of the nations population, they (64 or 65) constituted more than 20% of the Spelling Bee contestants .
  6. Three contestants, all of Indian origin, Vanya Shivashankar, Jairam Hathwar, and Srinath Mahankali, had siblings who have previously won the Scripps National Spelling Bee.
  7. Indian Americans have won for seven years in a row and all but four of the last 15 years.
  8. At the semi-final stage 29 of the 50 contestants were Americans of Indian origin.
  9. Seven of the ten finalists were Indian Americans.

Should Jihadi John have been killed at birth?

March 4, 2015

I was listening to a discussion this morning about who was to blame that Jihadi John (Mohammed Emwazi ) is what he is. The consensus seemed to be that it was not his parents, it was not the UK, it was not “the system”, it was not his schooling, it was not his childhood friends and it was not his University. Some blame clearly attached to the radical preachers he had been exposed to, but the primary blame and culpability lay with Jihadi John himself. In effect with his genes. His nature not his nurture.

(Of course I ignore all his companions and partners in cruelty and barbarity who think he is some kind of a hero destined for paradise).

And that brought to mind this story from last week about the quality control of Danish pigs:

TheLocal.seSwedish supermarket giant Ica has promised action after it emerged that hundreds of thousands of underweight piglets are killed every year in Denmark by banging their heads against the floor.

Hans Aarestrup, head of the Danish organization for swine producers, Danske Svineproducenter, told Swedish Radio’s news programme Ekot on Monday that about half a million piglets are killed every year for “humane” reasons.

“Instead of waiting for the weakest pigs to die, we kill them. The most humane way is to grab them by their hind legs and hitting them on the floor,” he said.

In the latest edition of Danske Svineproducenter’s magazine, they estimate that a farm with one thousand sows could save half a million Danish kroner a year if they put down all newborn pigs weighing less than a kilo, under the headline “Could it be a win-win situation to kill pigs at birth?”. …

We exercise quality control over all our manufactured goods. We exercise quality control over all domesticated pets and livestock. Even the Swedish indignation about the manner of the killing of the Danish piglets is about the method – not about the quality control. We cull wolves and deer and reindeer and even “threatened species” (lions, tigers, giraffes) in an effort to maintain “healthy genes”.  We even exercise some quality control over humans before birth when we abort severely disabled foetuses.

Suppose now that gene testing at birth (or before) could have revealed the monster that Jihadi John was going to become. The underlying assumption is that his genes alone – and not his nurture – were to blame. Suppose that gene testing had revealed that he was like an underweight Danish piglet. That there was “high” probability that his gene mix would lead him to be a monster. Should quality control have kicked in? Should he then have been “eliminated” at birth?

And who else would then fail to pass the quality control gate at birth and end up in the “reject” pile? There is a case for a new eugenics.

Domesticating tigers to ensure their survival

March 1, 2015

Tigers cannot survive without human intervention. They are just not capable of handling the shrinking of their traditional habitats and the changing environment. They are not evolving fast enough. Traditional – and misguided – conservation is all about trying to maintain some limited habitats in which they can survive without change. That is a misguided policy just because it tries to freeze the tiger into a genetic dead-end in an artificially maintained habitat. The tiger reserves are then little more than large zoos.

If tigers are to survive they must change within themselves. They need to adapt genetically. They have to adapt and move on. To change is to be alive. Not to change is to die. And a species which will not change “deserves” to go extinct. Traditional “conservation” is temporary and unsustainable. Conservation is stagnation.

I have long felt that real conservation must consist of helping threatened species to adapt genetically, not just freeze them into an artificial, temporary and unsustainable habitat. Of course changing a species genetically means that the unchanged species disappears. But that’s life.

Genetic adaptation – not stagnating conservation – is the way to help threatened species

So this apparently bizarre suggestion by a State Minister in Madhya Pradesh is not as crazy as it may first sound. A true, sustainable survival of tigers requires that they adapt such that they can continue living among humans without threatening humans. And that may well be a form of “humanisation” if not of “domestication”.

Deccan HeraldIn a bizarre suggestion, a senior Madhya Pradesh minister has sought a law that allows people to domesticate or keep as pets big cats like lions and tigers for their conservation.

Animal Husbandry, Horticulture and Food Processing Minister Kusum Mehdele, in a proposal sent to the state’s forest department, has cited legal provisions in some African and South-East Asian countries like Thailand which have helped bring about an increase in the population of the big cats.

Noting that there are various projects in the country for conservation of tigers, the minister, however, said that although crores of rupees have been spent on these projects, there has been no surprising increase in tiger numbers.

In Thailand and some other nations, there is a legal recognition to people for keeping tigers and lions as pets, she said, adding the number of such animals is increasing in a surprising way in these countries.

If such a possibility can be thought over, then necessary action should be undertaken and guidelines passed on, she said in the proposal sent to state Forest Minister Gaurishankar Shejwar in September last year.

The suggestion has, of course, been ridiculed by the traditional “conservationists” who are all into trying to keep the tiger and its world unchanged – frozen in an artificial environment which is unsustainable.

Indian claims of the recovery of tiger numbers may be overestimated:

Data released in January suggested India was home to 30 per cent more tigers than four years ago, with numbers rising from 1,706 in 2010 to 2,226 in 2014. Now conservation experts from the University of Oxford, the Indian Statistical Institute and the Wildlife Conservation Society have cast doubt on the assertion, suggesting the statistics were the result of a flawed method commonly used in censuses of tigers and other rare wildlife.

In Norway, more sun correlates to reduced inherited fertlity and greater infant mortality

January 10, 2015

There is a new intriguing paper from The Norwegian University of Science and Technology (NTNU):

G. R. Skjaervo, F. Fossoy, E. Roskaft. Solar activity at birth predicted infant survival and women’s fertility in historical Norway. Proceedings of the Royal Society B: Biological Sciences, 2015; 282 (1801): 20142032 DOI:10.1098/rspb.2014.2032

Researchers studied Norwegian church records of 9,000 people from the period 1750-1900 and looked at life history variables and compared them with environmental factors including solar activity.

NTNU Press Release: Skjærvø and her colleagues found that children born in the years with lots of solar activity had a higher probability of dying compared to children who were born in the years with less solar activity.

On average, the lifespan of children born in years that had a great deal of solar activity was 5.2 years shorter than other children. The largest difference was in the probability of dying during the first two years of life.

Children who were born in years with lots of sunshine and who survived were also more likely to have fewer children, who in turn gave birth to fewer children than others. This finding shows that increased UV radiation during years of high solar activity had an effect across generations.

Skjærvø used information on the number of sunspots as an indication of the amount of UV radiation in a given year. The number of sunspots reaches a maximum every 11 years on average, which results in more UV radiation on Earth during years with high sunspot and solar activity.

UV radiation can have positive effects on human vitamin D levels, but it can also result in a reduction of vitamin B9 (folate). It is known that low folate levels during pregnancy are linked to higher child mortality.

The NTNU study showed that families from the lowest socio-economic groups were most affected by UV radiation. This is probably related to the time period Skjærvø studied, which was a time of clear class distinctions in Norway, especially in rural areas. Women who worked in the fields were more exposed to the sun than other women. In many cases they also had a poorer diet.

If the primary mechanism for such connections is through UV radiation, then it presumably does not have the same impact on those with darker skin. But I suppose that the records from tropical or equatorial regions are not as comprehensive or reliable as old Norwegian church records.

“Filthy” Vikings were plagued by gut parasites

January 5, 2015

The observations of a 10th century Arab traveller, Ahmad ibn Fadlān ibn al-Abbās ibn Rāšid ibn Hammād, about the hygiene of the Vikings more than a thousand years ago, are being confirmed by new DNA analyses. Ibn Fadlan describes the Eastern Vikings while the new DNA studies are about the Western Vikings, but their living conditions and habits would have been very similar. ScienceNordic reports that a new DNA study “conducted on thousand-year-old parasite eggs recovered from Viking faeces, shows that both the Vikings and their domestic animals were plagued by parasites — which most likely enjoyed excellent living conditions in a dirty world in which domestic animals and humans lived in unhygienically close proximity to each other”.

The paper is published in the Journal of Parasitology:

The shameful vilification of James Watson

December 12, 2014

In a recent post about the Nobel ceremony I observed that James Watson who had sold his Nobel medal had it returned to him by the purchaser. Apart from his recognition along with Crick and Wilkins for their DNA work, he has been and still is one of the most important evolutionary biologists of our time. But he has become persona non grata now with the self-appointed guardians of public morality and the prevailing “political correctness” which disallows “intelligence” – however it may be defined – from being in any way dependent upon the genetic variations between different human populations. His vilification and downfall was a rapid business in 2007, even though, everything Watson got in trouble for saying was entirely correct” as Gene Expression pointed out in October 2007:

It’s difficult to name many more important living figures in 20th century biology than James Watson. He ushered in the current age of molecular biology with his achievements in 1953, he built up one of the world’s greatest biological research facilities from damn near scratch, and he is a former head of the Human Genome Project.
Given such an august curriculum vitae, you would think that this man perhaps understands just a few things about genetics. But given only the condescending media coverage, you’d think this eminent geneticist was somehow “out of his depth” on this one.
In his interview with the Times on Oct. 14th, we learned that:

… [Watson] is “inherently gloomy about the prospect of Africa” because “all our social policies are based on the fact that their intelligence is the same as ours – whereas all the testing says not really”, and I know that this “hot potato” is going to be difficult to address.

These thoughts were a continuation of an important theme in his book Avoid Boring People:

… there is no firm reason to anticipate that the intellectual capacities of peoples geographically separated in their evolution should prove to have evolved identically. Our wanting to reserve equal powers of reason as some universal heritage of humanity will not be enough to make it so.

Although Watson’s book had already been out for a month with these more euphemistic, but still obvious, comments on race and intelligence, no one expressed any outrage. In fact the reviews were reverential and universally positive.
The explicit reference to intelligence and people of African heritage in his interview was clearly a violation of a much more formidable taboo. Still I am not aware of there being much noise about it until Oct. 17th when the Independent caused an immediate stir by calling attention to the remarks: Africans are less intelligent than Westerners says DNA pioneer.
There’s no point in rehashing the rapid sequence of events in detail: several of Watson’s sold-out speaking engagements were cancelled, many critical articles appeared in the British press, trailed by the American press a few days later, hundreds of blogs were fuming with negative commentary, including ones by the editors of Scientific American and Wired Magazine, a number of associations issued statements condemning his words, and soon he was suspended from his chancellorship at Cold Spring Harbor. Watson cancelled his already ruined book tour and flew home to tend to the destruction. It was too late; the eminent biologist retired in disgrace on Oct. 26th. 
One thing, though, was conspicuously missing from this whole irritating denouement: any semblance of factual refutation. There is good reason for this: everything Watson got in trouble for saying was entirely correct!

Gene Expression goes on to show that the data support what James Watson said.

Unfortunately our esteemed band of sputtering media scientists forgot to provide, in all of these instances, any of their allegedly voluminous citations to the contrary. Allow me, then, to take a different position, with the added benefit of evidence: ………

………. 65 psychometric intelligence study citations for sub-Saharan Africa, collected in IQ & Global Inequality, Race Differences in Intelligence, and IQ & the Wealth of Nations. The citations cover 47% of SS African countries or 78% of the people by national population numbers. The studies vary in quality, sample size, and representativeness, but broadly agree in their findings. Representative studies of the school age population with large sample sizes do not exhibit higher scores, much less scores that approach anything like European norms. …..

….. Thus typical African IQ scores of 70 and below can still be taken as a reliable finding. It is not simply the manufactured data of racialist researchers, or a byproduct of inadequate testing procedures. And, more importantly from the standpoint of the Watson controversy, certainly no reliable body of evidence has shown anything like parity with typical European scores.

The entire episode and shameful treatment meted out to Watson by an unscrupulous and sensationalist media and by politically correct but cowardly members of the scientific community was based, I think, on

  • the intellectual laziness in defining what “race” is, and the sloppy way in which the term is used, and 
  • a fear of confronting the ideological notion that some meaningless, diffuse “equality” of all humans transcends and overrides the real genetic variations due to ancestry

We use the term “race” colloquially and loosely and for convenience. There is no firm scientific definition of what constitutes a “race”. Often it is taken – wrongly – to be just a difference of skin colour. The politically correct brigade claim that race is a “social construct” but this is just nonsense. An “African-American” carries genes from his African ancestry and not any particular social behaviour from his ancestors. But “race” is also a dynamic term and shifts with the generations of man. The races we recognise and classify humans into today, is based on the prevailing groupings of populations that are convenient today. Fifty generations ago the “races” of that time would have been quite different. And fifty generations from now they will be quite different to the “races” we recognise today. The classification is about ancestry and is based on (or should be based on) the separate packages of genetic characteristics (some visible and some not) which are discernible and allow the grouping and classification of populations.

It seems perfectly logical, and is highly probable, that humans, though they may have originated from just a few relatively small populations out of Africarabia, have then over the next 5,000 generations, continued evolving in situ, giving the genetic diversity and the consequent physical diversity that we see today. The geographical populations we observe today are the result both of evolution in situ and a plethora of admixtures as people have migrated and mixed over the last 100,000 years. There were no “African-Americans” 50 generations ago. But already “African-Americans” today are different to “Africans” and both continue to evolve and develop in situ. It is quite unlikely that “African-American” or “Asian-British” or “Turkish-Germans” or “Chinese-Indonesian” will be classifications of race or ethnicity that will be used 50 generations from now. This geographically evolved and still evolving diversity, already shows up as genetic differences not only of skin, eye and hair colour but also as differences in disease resistance, physical characteristics, athletic capabilities, behaviour and surely many more invisible (including mental) characteristics.

We have no difficulty in accepting that different populations (effectively different races in colloquial usage) have differences of physical characteristics due to their genetic ancestry. There is no great outrage now that recent studies point to some genetic differences that Tibetans have which may give them an advantage in absorbing oxygen at high altitudes. Similarly there are no screams when other genetic studies suggest that East Africans (Kenyans and Ethiopians in the main) have some genes – or combination of genes – which give them better endurance and therefore – given good nourishment – lead to better performance as long distance runners. West Africans, or those of West African descent, it seems may have some genetic advantages which make them the fastest sprinters over short distances. African genes also seem to give a lower fat content in body mass – which is genetic – and may be one explanation why their performance as swimmers is less than exceptional. That Indians are more prone to Type 2 diabetes than other “races” is not indignantly opposed but just taken for the observation it is. Indian-Americans (3 generations) are already exhibiting lower rates than their Indian ancestry would indicate. Japanese have very low rates of heart disease but already (in less than 6 generations) Japanese-Hawaiians have heart disease rates that are 2 -3 times higher.

It is illogical to assume that these genetic variations between different geographic populations ( colloquially “races”) have only manifested themselves as physical variations. It is highly probable and probably inevitable that these genetic developments will also have affected the brain, its functioning and behaviour. And intelligence.

“Intelligence” is many things to many people and – by most definitions – more than just an IQ test. The IQ test only really measures the ability to do the test. Nevertheless the IQ test results do seem to correlate well to whatever we may choose to call intelligence. There is without doubt a genetic component to both intelligence and IQ test results. IQ test measurements do show that results are significantly lower – for whatever reason –  among sub-Saharan African populations – on average. If intelligence has a genetic component and the colloquial use of the term “race” refers to an identifiable population exhibiting a certain package of genetic characteristics, then it is quite likely that the different genetic packages lead to some differences of intelligence.

If it is acceptable – and not racist – to observe that there are genetic differences in physical characteristics between the “races” of today, then it is just as acceptable and no more racist to observe that there are genetic differences of intelligence between the “races” of today.

That is all that Watson said.

(What “intelligence” actually is or may be is another story for another day).

Criminal fathers have stupid sons – Swedish study

December 2, 2014

I first thought this new paper was something of a hoax, but perhaps it isn’t. Our genes are the ultimate multi-taskers. Not only do they combine to cooperate with a variety of other genes to express certain characteristics, each gene seems to take part in many such cooperations in many other teams of genes.. If criminal behaviour is (even partly) genetic, and if intelligence is also (partly) genetic, then it is not impossible that the genetic factors which lead to increased criminal behaviour in the parent may also cause (directly or indirectly) lower cognitive ability (intelligence) in offspring. Of course I would expect that the tendency to have lower intelligence will also be exhibited in the parent.

Swedish and Finnish researchers have looked at data for over 1,000,000 men and “found that men whose fathers had any criminal convictions tended to have lower cognitive-ability scores than men whose fathers had no such history”.

A. Latvala, R. Kuja-Halkola, N. Langstrom, P. Lichtenstein. Paternal Antisocial Behavior and Sons’ Cognitive Ability: A Population-Based Quasiexperimental Study. Psychological Science, 2014; DOI: 10.1177/0956797614555726

From the Association for Psychological Science press release:

Sons whose fathers have criminal records tend to have lower cognitive abilities than sons whose fathers have no criminal history, data from over 1 million Swedish men show. The research, conducted by scientists in Sweden and Finland, indicates that the link is not directly caused by fathers’ behavior but is instead explained by genetic factors that are shared by father and son. …….. 

… Research looking across generations in families has shown that children of parents who engage in “antisocial” behaviors — such as rule-breaking, aggressive, or violent behavior — are at greater risk for various negative outcomes, including criminality, psychiatric disorders, substance use, and low academic achievement. And research has also shown that individuals who engage in antisocial behaviors tend to have poorer cognitive abilities than those without antisocial tendencies.

Latvala and colleagues wanted to combine these two strands of research to investigate how parents’ antisocial behaviors might affect their children’s cognitive development.

“We wondered whether children of antisocial parents also have lower cognitive ability than children of non-antisocial parents, and if so, whether compromised cognitive functioning might be part of the inherited risk for antisocial behavior,” says Latvala.

The researchers took advantage of extensive data collected from Swedish residents, including data on cognitive ability acquired as part of compulsory military conscription and data on antisocial behavior (in this case, defined as criminal convictions) obtained from a national crime register.

Looking at data from over 1,000,000 men, the researchers found that men whose fathers had any criminal convictions tended to have lower cognitive-ability scores than men whose fathers had no such history.

And this association seemed to be influenced by the severity of the fathers’ criminal history:

“Perhaps most surprising was the clear gradient seen in the magnitude of the association with sons’ cognitive ability by severity of fathers’ criminality: The more severe crimes the father had committed, the poorer was the sons’ cognitive performance,” explains Latvala.

But did fathers’ antisocial behavior have a direct causal effect on sons’ cognitive ability, or could the link be explained by shared genetic factors?

To find out, the researchers compared the link between fathers’ criminal history and sons’ cognitive ability across cousins whose fathers had varying relationships to each other.

Specifically, they examined the link in cousins whose fathers were half-siblings (sharing about 25% of their genetic makeup), cousins whose fathers were full siblings or fraternal twins (sharing about 50% of their genetic makeup), and cousins whose fathers were identical twins (sharing 100% of their genes).

If fathers’ antisocial behavior directly caused sons’ lower cognitive ability, the link would remain equally strong across the comparisons of varying genetic relationships.

The data, however, suggested otherwise. When the researchers took the varying genetic relationships into account, the association between fathers’ criminality and sons’ cognitive ability gradually diminished.

“Free will” is further circumscribed as two genes associated with violence are identified

October 29, 2014

The range of application of human “free will” is increasingly being circumscribed as we identify genes which are associated with specific behavioural characteristics. This is not to say that any gene or set of genes makes certain specific behaviour inevitable – but it does say that that particular behaviour is more probable for that individual. Perhaps it is more accurate to say that an individual’s gene set defines (and therefore constrains) the envelope of possible behaviour. But that itself means that he can only exercise “free will” within the envelope of possible behaviour that is available to him.

A new study from Finland has identified two genes associated with violent crime. The study of 900 Finnish criminals is published in Molecular Psychiatry.

MedPage:

Variants in two genes were significantly more common in Finnish criminals convicted of multiple violent crimes compared with the general population, researchers said.

Statistical analysis indicated that 5% to 10% of all severe violent crime in Finland could be attributed to these variants, affecting the genes for monoamine oxidase A (MAOA) and CDH13, a neuronal membrane adhesion molecule, according to Jari Tiihonen, MD, PhD, of the Karolinska Institute in Stockholm, and colleagues.

Offenders who had committed 10 or more serious violent crimes were significantly more like to carry one of several loss-of-function variants in the MAOA gene (odds ratio 2.66, 95% CI 1.60-4.42) or the so-called rs11649622 variant in the CDH13 gene (OR 2.72, 95% CI 1.77-4.15), versus participants in population-based survey studies in Finland who were considered representative of the general population.

Criminal offenders with no violent crime convictions showed no increases in risk of carrying the flagged MAOA/CDH13, with an OR of 1.12-1.13 relative to the population-based sample, which did not approach statistical significance.

In their report published online in Molecular Psychiatry, they acknowledged that crime “is a complex phenomenon, and the outcome is shaped by both genetic and environmental factors.”

But that doesn’t mean that genetic contributors cannot be identified, they argued. “It is plausible that while research of the genetic background of criminal or violent behavior is hampered by many confounding factors, focusing on extreme phenotypes might yield more robust results,” Tiihonen and colleagues wrote.

J Tiihonen et al, Genetic background of extreme violent behavior, Molecular Psychiatry , (28 October 2014), doi:10.1038/mp.2014.130

This may not have much practical application yet, and there are certainly many more genes which also predispose to violence and a genetic screening for “violent” tendencies is not coming any time soon. Violent tendencies are also certainly not only due to genes and nurture surely has a very significant part to play.

AbstractIn developed countries, the majority of all violent crime is committed by a small group of antisocial recidivistic offenders, but no genes have been shown to contribute to recidivistic violent offending or severe violent behavior, such as homicide. Our results, from two independent cohorts of Finnish prisoners, revealed that a monoamine oxidase A (MAOA) low-activity genotype (contributing to low dopamine turnover rate) as well as the CDH13 gene (coding for neuronal membrane adhesion protein) are associated with extremely violent behavior (at least 10 committed homicides, attempted homicides or batteries). No substantial signal was observed for either MAOA or CDH13 among non-violent offenders, indicating that findings were specific for violent offending, and not largely attributable to substance abuse or antisocial personality disorder. These results indicate both low monoamine metabolism and neuronal membrane dysfunction as plausible factors in the etiology of extreme criminal violent behavior, and imply that at least about 5–10% of all severe violent crime in Finland is attributable to the aforementioned MAOA and CDH13 genotypes.

I conceive an individual’s genes as defining the range of behaviour available to a human and his “nurture” as then determining his actual behaviour by the exercise of what we call “free will”. What is becoming increasingly obvious though, is that any individual’s “free will” is severely circumscribed. The application of “free will” is restricted to be within the envelope of behaviour that the genes allow.

Behaviour envelopes

I envision an individual whose limits are set by his genes. He cannot think faster or run faster or behave differently to what his genes allow. Thus no amount of “free will” (or nurture) could get an individual to behave outside the envelope of his possible behaviour as set by his individual set of genes.

 

Height is 80% nature (genetics) and 20% nurture

October 5, 2014

A DNA study of more than 250,000 people has doubled the number of identified genetic factors which determine height to around 700 variants in over 400 genome regions. But the factors identified so far may be only 20% of the genetic factors which apply.

EurekAlert:

A study which examined data on DNA from more than 250,000 people, published on October 6 in Nature Genetics, roughly doubles the number of known genome regions involved in height to more than 400. It also revealed that more than half of the factors involved in determining height are explained by simple common genetic variation – the sort of genetic variation that exists in more than 1 in 10 people.

The collaboration, co led by the University of Exeter Medical School and part-funded by the Wellcome Trust, involved more than 450 experts from well over 300 institutions in Australia, the USA and several European countries. Together, they form the aptly named GIANT consortium. The study is the largest of its kind to date. They checked more than 2 million common genetic factors – those shared by at least five per cent of participants. From this they found 697 genetic variants in 424 regions of the genome that are related to height. The findings represent a massive stride forward in an area of research in which virtually nothing was known as recently as 2007.

Professor Tim Frayling, of the University of Exeter Medical School, oversaw the study. He said: “It’s common knowledge that people born to tall parents are more likely to be tall themselves. Most of this is down to the variations in our DNA sequence that we inherit from our parents – the different versions of all our genes. In 2007 we published the first paper that identified the first common height gene, and since then the research has come on leaps and bounds. We have now identified nearly 700 genetic variants that are involved in determining height. This goes a long way towards fulfilling a scientific curiosity that could have real impact in the treatment of diseases that can be influenced by height, such as osteoporosis, cancer or heart disease. It also a step forward towards a test that may reassure parents worried that their child is not growing as well as they’d hoped – most of these children have probably simply inherited a big batch of “short genes.”

Height is determined by a very large, but finite, number of contributing factors. Genetic causes are located throughout the genome, and environmental factors such as diet also play a role. The GIANT consortium is working towards identifying the thousands of hidden factors which have varying effects in height, ranging from minute to gigantic. The results arise from analysis of DNA data on 253,288 individuals of European ancestry. The research team says increasing sample sizes of this magnitude make it far easier to find commonalities that determine traits such as size.

Lead author Dr Andrew Wood, of the University of Exeter Medical School, said: “Our findings have helped to identify a large proportion of the genetic architecture that contributes to determining our height. We know that as a population we have become taller over the last few generations, because of factors including improved nutrition. But more than 80 per cent of the factors in height variation are known to be down to genetics, with the rest caused by environmental factors. Thanks to advances in technology, we now have access to far greater quantities of DNA data. These data sets are proving to be a genetic treasure trove which has enabled us to shed light on height, and we expect to continue to make significant advances, both in this field and in other human traits. Our results suggest that massive human genetic studies, possibly into the millions, will continue to uncover all the subtle effects of our genetic variation that influence our health, behaviour, body shape and all aspects of what makes us who we are.”

Dr Joel Hirschhorn, of Boston Children’s Hospital and the Broad Institute of MIT and Harvard, is leader of the GIANT Consortium and co-senior investigator on the study. Dr Hirschhorn said: “When you double the sample size and increase your statistical power, you can make new discoveries. Our results prioritise many genes and pathways as important in skeletal growth during childhood. Without a highly collaborative model, there’s no way we could get this work done. We can now explain about 20 percent of the heritability of height, up from about 12 percent where we were before.”

Professor Peter Visscher, of the University of Queensland, Australia, said: “The study narrows down the genomic regions that contain a substantial proportion of remaining variation—to be discovered with even larger sample sizes.”

Professor Frayling said: “The genes and pathways involved in height should help facilitate future studies, and we have made them publicly available to this end. We believe that large genetic studies could yield similarly rich lists in a variety of other traits, and could generate new biological hypotheses and motivate future research into the basis of human biology and disease.”

 

More women than men – throughout history

September 26, 2014

The Max Planck Institute for Evolutionary Anthropology is pioneering many new techniques of investigative genetics and is causing minor revolutions in many areas of anthropology. Perhaps the best known of these is Svante Pääbo and his group’s work on extracting and analysing ancient DNA.  Their work on the Neanderthal genome is changing the previously accepted history of Modern Humans and their relationships with Neanderthals, Denisovans and other ancient branches of homo erectus.

A new paper reports on a DNA study of 623 males from 51 different populations and comes to the conclusion that throughout history women have outnumbered men. The study compared the paternally-inherited Y chromosome (NRY) with maternally inherited mitochondrial DNA (mtDNA). The researchers developed a high-resolution Y chromosome sequencing assay that allowed them to get paternal and maternal histories of similar quality and resolution. Female populations were larger before the out-of-Africa migration(s) and remained so throughout almost all subsequent migrations. Women migrated more (presumably as they were married out) and men stayed put more. For most of our history a greater proportion of women in the population reproduced than men leading to females making a larger genetic contribution to the current global population than males did. Men tended to fertilise multiple females (perhaps an indicator of polygyny).

CBS News: …. people in East Asia and Europe have larger genetic differences for paternal than for maternal DNA, suggesting high levels of female migration. In contrast, populations in Africa, Oceania and the Americas have bigger differences for maternal DNA than for paternal DNA.

Human paternal and maternal demographic histories: insights from high-resolution Y chromosome and mtDNA sequences, Sebastian Lippold, Hongyang Xu, Albert Ko, Mingkun Li, Gabriel Renaud, Anne Butthof, Roland Schroeder and Mark Stoneking, Investigative Genetics 2014, 5: 13

Eurekalert:

Female populations have been larger than male populations throughout human history, according to research published today in the open access journal Investigative Genetics. The research used a new technique to obtain higher quality paternal genetic information to analyse the demographic history of males and females in worldwide populations.

The study compared the paternally-inherited Y chromosome (NRY) with maternally inherited mitochondrial DNA (mtDNA) of 623 males from 51 populations. The analysis showed that female populations were larger before the out-of-Africa migration and remained so throughout almost all subsequent migrations. The main drivers of this trend are likely to be processes such as polygyny, where one male mates with many females, and the fact that in most societies, women tend to move to live with their husbands. This has resulted in females making a greater genetic contribution to the global population than males.

Previous research on genetic history has used different techniques to analyse NRY and mtDNA, which has led to an ascertainment bias in the results. In this study, researchers from the Max Planck Institute for Evolutionary Anthropology developed a high-resolution Y chromosome sequencing assay that allowed them to get paternal and maternal histories of similar quality and resolution, so they could make a direct comparison. The results confirmed previous findings that when comparing human populations on a global scale, there are greater genetic differences in paternal NRY than in mtDNA. However, these differences are not as large as previously thought and the authors were surprised to see substantial variation in relative amounts of NRY vs. mtDNA differentiation at the regional level.

The authors argue that using this new technique, greater analysis can be undertaken at a regional level to create a clearer picture of the paternal and maternal influences on specific populations. In the African populations they studied, they saw lower paternal genetic diversity, which may be a direct result of the Bantu expansion into eastern and southern Africa beginning about three thousand years ago. In samples taken from the Americas, initial results suggest higher maternal genetic diversity, indicating that there were fewer males than females among the original colonisers.

Dr. Mark Stoneking, Department of Evolutionary Genetics, Max Planck Institute, an author on the paper, said: “Our new sequencing technique removes previous biases, giving us a richer source of information about our genetic history. It allows us to take a closer look at the regional differences in populations, providing insights into the impact of sex-biased processes on human genetic variation.”


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