MHC-dissimilar mating in Brazil

This seems to parallel previous findings on European Americans.

Opposites attract -- how genetics influences humans to choose their mates

Vienna, Austria: New light has been thrown on how humans choose their partners, a scientist will tell the annual conference of the European Society of Human Genetics today (Monday May 25). Professor Maria da Graça Bicalho, head of the Immunogenetics and Histocompatibility Laboratory at the University of Parana, Brazil, says that her research had shown that people with diverse major histocompatibility complexes (MHCs) were more likely to choose each other as mates than those whose MHCs were similar, and that this was likely to be an evolutionary strategy to ensure healthy reproduction.

Females' preference for MHC dissimilar mates has been shown in many vertebrate species, including humans, and it is also known that MHC influences mating selection by preferences for particular body odours. The Brazilian team has been working in this field since 1998, and decided to investigate mate selection in the Brazilian population, while trying to uncover the biological significance of MHC diversity.

The scientists studied MHC data from 90 married couples, and compared them with 152 randomly-generated control couples. They counted the number of MHC dissimilarities among those who were real couples, and compared them with those in the randomly-generated 'virtual couples'. "If MHC genes did not influence mate selection", says Professor Bicalho, "we would have expected to see similar results from both sets of couples. But we found that the real partners had significantly more MHC dissimilarities than we could have expected to find simply by chance."

Within MHC-dissimilar couples the partners will be genetically different, and such a pattern of mate choice decreases the danger of endogamy (mating among relatives) and increases the genetic variability of offspring. Genetic variability is known to be an advantage for offspring, and the MHC effect could be an evolutionary strategy underlying incest avoidance in humans and also improving the efficiency of the immune system, the scientists say.

The MHC is a large genetic region situated on chromosome 6, and found in most vertebrates. It plays an important role in the immune system and also in reproductive success. Apart from being a large region, it is also an extraordinarily diverse one.

"Although it may be tempting to think that humans choose their partners because of their similarities", says Professor Bicalho, "our research has shown clearly that it is differences that make for successful reproduction, and that the subconscious drive to have healthy children is important when choosing a mate."

The scientists believe that their findings will help understanding of conception, fertility, and gestational failures. Research has already shown that couples with similar MHC genes had longer intervals between births, which could imply early, unperceived miscarriages. "We intend to follow up this work by looking at social and cultural influences as well as biological ones in mate choice, and relating these to the genetic diversity of the extended MHC region", says Professor Bicalho.

"We expect to find that cultural aspects play an important role in mate choice, and certainly do not subscribe to the theory that if a person bears a particular genetic variant it will determine his or her behaviour. But we also think that the unconscious evolutionary aspect of partner choice should not be overlooked. We believe our research shows that this has an important role to play in ensuring healthy reproduction, by helping to ensure that children are born with a strong immune system better able to cope with infection."

I had previously posted some more abstracts from ESHG 2009. Here is the abstract from this study:

New evidences about MHC-based patterns of mate choice

M. Bicalho, J. da Silva, J. M. Magalhães, W. Silva;

Major Histocompatibility Complex (MHC) genes code for cell surface proteins, which plays an important role in immune recognition. In the late 1970s, Yamazaki observed that inbred mice were more likely to mate with partners having MHC dissimilar genes. Females’ preference for MHC dissimilar mates was also observed in other vertebrate species, including humans. It has been shown that MHC influences mating selection mediated by preferences based on body odor. What’s the functional significance of these findings, if some? It was assumed that through olfactory cues MHC-related evolved as a strategy to maximize the offspring MHC heterozygosity. Parents with dissimilar MHCs could provide their offspring with a better chance to ward infections off because their immune system genes are more diverse. MHC genotype might be used to signal relatedness and immune response genotypes through.

We investigated whether husband-wife couples (n=90) obtained from LIGH’s database were more MHC-similar/dissimilar in comparison to random couples generated from the same database (n=55 000) as to collect evidence of MHC influence in MHC-based patterns of mate choice.

The individuals HLA typing (Class I and Class II) was performed by PCR-SSP or PCR-rSSOP using a commercial kit ( One Lambda Inc., Canoga Park. CA, USA).

Our results and comparisons ( p= 0,014) suggest that couples seem to be formed by individuals with less HLA similarity, corroborating the hypothesis that HLA antigens, especially Class I, may influence mate selection and marriages in humans.

Inbreeding and the Spanish Hapsburgs

Since, presumably, the remains of these royals have been preserved, it would be interesting at some future date to carry out an ancient DNA study which would show exactly which deleterious alleles contributed to the morbidity of the Spanish Hapsburgs.

PLoS ONE doi:10.1371/journal.pone.0005174

The Role of Inbreeding in the Extinction of a European Royal Dynasty

Gonzalo Alvarez et al.

Abstract

The kings of the Spanish Habsburg dynasty (1516–1700) frequently married close relatives in such a way that uncle-niece, first cousins and other consanguineous unions were prevalent in that dynasty. In the historical literature, it has been suggested that inbreeding was a major cause responsible for the extinction of the dynasty when the king Charles II, physically and mentally disabled, died in 1700 and no children were born from his two marriages, but this hypothesis has not been examined from a genetic perspective. In this article, this hypothesis is checked by computing the inbreeding coefficient (F) of the Spanish Habsburg kings from an extended pedigree up to 16 generations in depth and involving more than 3,000 individuals. The inbreeding coefficient of the Spanish Habsburg kings increased strongly along generations from 0.025 for king Philip I, the founder of the dynasty, to 0.254 for Charles II and several members of the dynasty had inbreeding coefficients higher than 0.20. In addition to inbreeding due to unions between close relatives, ancestral inbreeding from multiple remote ancestors makes a substantial contribution to the inbreeding coefficient of most kings. A statistically significant inbreeding depression for survival to 10 years is detected in the progenies of the Spanish Habsburg kings. The results indicate that inbreeding at the level of first cousin (F = 0.0625) exerted an adverse effect on survival of 17.8%±12.3. It is speculated that the simultaneous occurrence in Charles II (F = 0.254) of two different genetic disorders: combined pituitary hormone deficiency and distal renal tubular acidosis, determined by recessive alleles at two unlinked loci, could explain most of the complex clinical profile of this king, including his impotence/infertility which in last instance led to the extinction of the dynasty.

Link

Sexy parents produce sexy daughters (but not sons)

A very interesting new paper in Animal Behaviour regarding the inheritance of masculinity/famininity and attractiveness. On the left are composites of 10 attractive parents and their daughters, and on the right composites of 10 unattractive parents and their daughters.

Not surprisingly, the attractive female looks similar to another facial composite in a recent study on facial correlates of sociosexuality by authors from the same institution (University of St. Andrews in the UK).

The difference between Fisherian runaway selection and "good genes" theory -mentioned below- is that in the former, a "sexy" trait is selected even though it has no adaptive value (such as the peacock's tail), while in the latter the latter the "sexy" trait is that which signifies good genetic qualities (e.g. health).

From the paper:

Our findings are supportive of both Fisherian processes and good genes theory. Both parents contributed to the attractiveness and femininity of daughters. We found that daughter's attractiveness was predicted independently by father's attractiveness and mother's femininity (and therefore, by default, mother's attractiveness). Fisherian selection processes would suggest that men have evolved preferences for sexually dimorphic facial characteristics in opposite-sex partners, and through human evolution these preferences have increased the frequency of feminine facial characteristics such as a slender chin, full lips and large eyes in women. Good genes theory predicts the same finding, although it suggests that feminine facial characteristics must by definition signal good quality, including possible cues to immunocompetence, fertility, youthfulness, health and perhaps even maternal tendencies

...

We are perplexed as to why we did not find any evidence for the inheritance of attractiveness in males, through either the female or male parent. Attractiveness, by its own definition, should be sexy, and while we found evidence for sexy parents–sexy daughters, we did not find the parallel in male offspring. While masculine dads produced masculine sons, in this study, sexy parents did not produce sexy sons.

UPDATE : For a possible solution to this paradox, see next post.

Animal Behaviour doi: 10.1016/j.anbehav.2008.07.031

Sexy sons and sexy daughters: the influence of parents' facial characteristics on offspring

R. Elisabeth Cornwell, and David I. Perrett

Abstract

Choosing a mate to maximize fitness underlies all sexual selection theories. Key to understanding mate choice is the inheritance of particular traits. Using family photos, we evaluated the predictions made by sexual selection theories for human mate choice concerning the inheritance of facial characteristics and assortment in facial appearance of parents. We found that both fathers' and mothers' attractiveness predicted the facial attractiveness of daughters: ‘sexy daughters’. Fathers and sons were related to each other in facial masculinity but not attractiveness, providing only partial evidence for ‘sexy sons’. Mothers and sons did not relate in masculinity–femininity; neither did fathers and daughters. Parents were similar in attractiveness but masculine men were not partnered to feminine women. Our findings support some predictions of Fisherian selection processes and ‘good genes’ theory but are less consistent with ‘correlated response theory’ and the immunocompetence handicap principle.

Link

Y chromosomes and mtDNA of Sweden

It's interesting to see a study of the current population of a country. If one is interested in deep pre-historical origins, one must ensure that his sample has no known foreign ancestry among the lines of interest. But, if one is interested in the current and future course of the population, then the totality of the population must be sampled.

This is a good opportunity to track shifting gene frequencies due to immigration and/or differential fertility. It would be a good idea for countries to start spending some money on a genetic census of their population. This would not need to involve all the inhabitants, and could be carried out for the fraction of cost that governments pay to collect all sorts of other statistics. Such a census would provide an important source of data to future scientists investigating the demography of Europe during this transitional era.

From the paper:

Several haplogroups had interesting frequency patterns, but also wide confidence intervals, necessitating caution in the interpretations. The mtDNA haplogroup with the strongest geographical cline, U5b, is known to have high frequencies among the northern Saami population, consistent with our results (Tambets et al. 2004). The high frequency of the Y-chromosomal R1b in the south, observed also by Karlsson et al. 2006; is consistent with its abundance in Central Europe and Denmark (Semino et al. 2000; Brion et al. 2005). Haplogroup R1a1 is more common in Norway than in Sweden (Dupuy et al. 2006), and its high frequency in Värmland/Dalarna and Halland supports the historically plausible connection to Norway (Lindqvist, 2006). Y-chromosomal haplogroup N3 (Lappalainen et al. 2006) and mtDNA haplogroup H1f (Loogväli et al. 2004; Lappalainen et al. 2008) are common in Finland, and had increased frequencies in several Swedish counties with historical ties to Finland: Eastern Svealand was the most important destination of the Finnish immigration wave in the 1970's; in Norrland the Finnish influences date back to ancient times and in Dalarna to the 17th century (Pitkänen 1994).

When compared to previous knowledge of ethnic Swedes without immigration in their familial background (Lappalainen et al. 2008), the frequencies of several haplogroups showed effects of 20th century immigration from more distant countries. The Y-chromosomal I1a had decreased frequencies in Malmö and Gothenburg most probably due to replacement by haplogroups that are common among immigrants. African immigration contributes to the frequencies of mtDNA haplogroups L3*(xN,M) and L* (xL3) (Chen et al. 2000), and Y-chromosomal haplogroup A (Underhill et al. 2001; Jobling & Tyler-Smith 2003), while Near Eastern influence can be seen in mtDNA haplogroup U7 and possibly J (Richards et al. 2000; Abu-Amero et al. 2007; Achilli et al. 2007). Asian and American immigration can be observed in the slightly elevated frequencies of mtDNA haplogroups M, A, C, D and G (Quintana-Murci et al. 2004; Hill et al. 2007) and the Y-chromosomal O, K* and P* (Underhill et al. 2001; Jobling & Tyler-Smith 2003). The frequency of the Y-chromosomal haplogroup I1b may associate to immigrants from Balkan and Eastern Europe (Rootsi et al. 2004). In Malmö and Gothenburg immigration was the main contributor to their isolated positions in the Y-chromosomal PCA plot and probably also to the higher diversities compared to the surrounding populations. These phenomena were not observed in Stockholm, where most of the immigrants come from Finland (Statistics Sweden, http://www.scb.se).

Annals of Human Genetics doi: 10.1111/j.1469-1809.2008.00487.x

Population Structure in Contemporary Sweden—A Y-Chromosomal and Mitochondrial DNA Analysis

T. Lappalainen et al.

Abstract

A population sample representing the current Swedish population was analysed for maternally and paternally inherited markers with the aim of characterizing genetic variation and population structure. The sample set of 820 females and 883 males were extracted and amplified from Guthrie cards of all the children born in Sweden during one week in 2003. 14 Y-chromosomal and 34 mitochondrial DNA SNPs were genotyped. The haplogroup frequencies of the counties closest to Finland, Norway, Denmark and the Saami region in the north exhibited similarities to the neighbouring populations, resulting from the formation of the Swedish nation during the past millennium. Moreover, the recent immigration waves of the 20th century are visible in haplogroup frequencies, and have led to increased diversity and divergence of the major cities. Signs of genetic drift can be detected in several counties in northern as well as in southern Sweden. With the exception of the most drifted subpopulations, the population structure in Sweden appears mostly clinal. In conclusion, our study yielded valuable information of the structure of the Swedish population, and demonstrated the usefulness of biobanks as a source of population genetic research. Our sampling strategy, nonselective on the current population rather than stratified according to ancestry, is informative for capturing the contemporary variation in the increasingly panmictic populations of the world.

Link

Female voice pitch and ovulation

Biol Lett. 2008 Oct 8;

Vocal cues of ovulation in human females.

Bryant GA, Haselton MG

Recent research has documented a variety of ovulatory cues in humans, and in many nonhuman species, the vocal channel provides cues of reproductive state. We collected two sets of vocal samples from 69 normally ovulating women: one set during the follicular (high-fertility) phase of the cycle and one set during the luteal (low-fertility) phase, with ovulation confirmed by luteinizing hormone tests. In these samples we measured fundamental frequency (pitch), formant dispersion, jitter, shimmer, harmonics-to-noise ratio and speech rate. When speaking a simple introductory sentence, women's pitch increased during high- as compared with low-fertility, and this difference was the greatest for women whose voices were recorded on the two highest fertility days within the fertile window (the 2 days just before ovulation). This pattern did not occur when the same women produced vowels. The high- versus low-fertility difference in pitch was associated with the approach of ovulation and not menstrual onset, thus representing, to our knowledge, the first research to show a specific cyclic fertility cue in the human voice. We interpret this finding as evidence of a fertility-related enhancement of femininity consistent with other research documenting attractiveness-related changes associated with ovulation.

Link

Long-legged Chinese women have more children

Evolution and Human Behavior doi:10.1016/j.evolhumbehav.2008.06.003

Are longer legs associated with enhanced fertility in Chinese women?

Richard Fielding et al.

Abstract

Female height impacts fertility differently in western and nonwestern cultures. Leg length or relatively longer legs comprise key components of height and possibly indicates mate value. We examined the associations between height, its components, and reproductive outcomes in a large Chinese cohort. Multivariable regression was used to assess the association of height, leg length (standing minus sitting height) and relatively longer legs with number of offspring in a cross-sectional sample of 9998 Chinese people aged at least 50 years from Phase 2 of the Guangzhou Biobank Cohort Study recruited in 2005–2006. Older and less educated respondents had more children. Adjusted for age, childhood socioeconomic status (SES), and education, women with longer legs had more offspring; however, there was no such association in men. When stratified by childhood SES (reported parental material possessions), longer legs and relatively longer legs were most strongly associated with more offspring in women from poorer backgrounds. Fertility was specifically associated with longer legs and relatively longer legs in women only. The difference in the association of leg length to number of offspring by childhood SES suggests a preference advantage rather than a physiological advantage in being taller. However, these benefits were specific to reproductive success in women and particularly women from poorer backgrounds suggesting that social factors may have facilitated fertility.

Link

ESHG 2008 abstracts

The European Society of Human Genetics conference is coming up, and there are some very interesting abstracts.

Note: The ESHG site has updated with a notice that the abstracts are embargoed until their presentation time. Therefore, I have decided to remove the body of this post until then, although I think it is a bit weird to embargo something that one places on the public web. In any case, you can find the abstracts easily by going to the site above. (June 1): post restored.

The peopling of North Asia: Y and X perspectives

V. A. Stepanov, V. Kharkov, I. Khitrinskaya, O. Medvedeva, M. Spiridonova, A. Marusin, V. Puzyrev; Institute for Medical Genetics, Tomsk, Russian Federation.

Presentation Number: P07.056

To reconstruct the origin and evolution of human populations in North Asia we investigated the genetic diversity in 50 population samples (about 2000 individuals totally) using Y and X chromosome lineages. Y-chromosomal haplotypes were constructed with unique event polymorphisms (UEP) and STR markers according to Y Chromosome consortium (YCC) classification. SNP markers in a single 60 kb linkage disequilibrium region of ZFX gene was used to trace the X chromosomal population history. The genetic diversity of Y haplogroups was quite high (0.70 - 0.95) in most populations except few very isolated groups. The proportion of inter-population differences in the total genetic variability measured by Fst statistics is 17% for binary haplogroups and 19% for YSTR. Multidimensional scaling and principal component analysis revealed four major components in North Asian Y gene pool, reflecting the presence of Paleoasiatic (Q), Proto-Uralic (N3, N2), Eastern Asian (O, C), and Western Eurasian (R1, I, J) lineages. X-chromosomal haplotypes in North Asia are less divers (gene diversity within populations 0.65 - 0.80) and less differentiated (Fst = 4%) compared to Y lineages. The population clustering by X and Y gives, to a first approximation, a similar picture, and matrixes of genetic distances between populations for X and Y haplotypes significantly correlates. The age of genetic diversity generation and time of population differentiation demonstrates the Upper Paleolithic origin of major Y and X lineages and post-glacial population expansions. This work is supported by RFBR grants ##06-04-48274 and 07-04-01629.

The following seems to be a very important study; in particular the notion that particular Y chromosome/mtDNA haplogroups may be associated with higher or lower fertility may have implications about their distribution.

UPDATE (May 21): I did a quick and dirty analysis of the Y-haplogroup and mtDNA-haplogroup data from Bosch et al. (2006) (Ann Hum Genet. 2006 Jul;70(Pt 4):459-87.), and there is a -0.43 correlation between Y-haplogroup I and mtDNA-haplogroup H and a +0.46 correlation between Y-haplogroup R1 and mtDNA-haplogroup H. While not significant (with only 10 populations), this is definitely in the right direction for a selection effect for/against specific Y-DNA/mtDNA combinations.

... on the other hand, another quick and dirty analysis of 23 populations from Rootsi's survey on Y-haplogroup I and mtDNA frequencies from AJHG Volume 80, Issue 4, April 2007, Pages 759-768 didn't turn up any correlation. Perhaps, someone can look at possible correlations between Y-chromosome and mtDNA haplogroups in Europe to see if anything interesting turns up.

Male infertility induced by mtDNA/Y unfavorable combination? An association study on human mitochondrial DNA

S. C. Gomes1, S. Fernandes2, R. Gonçalves1, A. T. Fernandes1, A. Barros3, H. Geada4, A. Brehm1; 1Human Genetics Laboratory, University of Madeira, Funchal, Portugal, 2Genetics Department, Faculty of Medicine, University of Porto, Porto, Portugal, 3Centre of Reproductive Genetics A Barros, Porto, Portugal, 4Faculty of Medicine, University of Lisbon, Lisboa, Portugal.

Presentation Number: P07.084

There is growing evidence that certain mtDNA haplogroups determine a genetic susceptibility to various disorders bringing out the interest in the possible role of mtDNA background on the phenotype expression of mitochondrial genetic disorders. An association between haplogroup T and asthenospermia has been reported and several sublineages of haplogroup U were associated with differences in sperm motility and vitality. The deletion of some DAZ copies gene in 10-15% of azoospermic and oligospermic patients has been reported but also present in fertile men belonging to certain Y-haplogroups. The findings of one study have rarely been replicated by studies in other populations and conflicting associations have been reported. Our focus in this case-control study is to investigate the existence of other influences, besides a weak mtDNA background, promoting male infertility. The occurrence of a specific mtDNA variant associated to a certain Y-chromosome haplogroup could represent a vital link that will compromise the sperm function and be responsible for male infertility. A group of 99 infertile men and other one composed by 90 subjects with proven fertility were selected and analysed. The frequency of the combination mtDNA-haplogroup H (especially with the CRS sequence) and Y-haplogroup R was higher in fertile than in infertile men seemingly to be favorable to fertility. On the other hand, a considerable number of infertile men belonging to mtDNA-haplogroup H (CRS) and to Y-haplogroup I, associated to a specific DAZ gene deletion pattern- 2+4d, suggests a non favorable combination to male fertility.

The Bayash Roma: phylogenetic dissection of Eurasian paternal genetic elements

I. Martinovic Klaric, M. Pericic Salihovic, L. Barac Lauc, B. Janicijevic; Institute for Anthropological Research, Zagreb, Croatia.

Presentation Number: P07.110

The Bayash consist of numerous and small Romani groups speaking different dialects of the Romanian language and living dispersedly in Croatia, Hungary, Bosnia and Herzegovina, Serbia, Romania, Bulgaria, and to the lesser extent in Macedonia, Greece, Ukraine, Slovakia and Slovenia. Larger Bayash groups migrated to Croatia most likely during the 19th century, after abolition of slavery in Romania. Molecular architecture and the origin of the Croatian Bayash paternal gene pool was addressed by analysing 151 Bayash Y chromosomes from two Croatian regions, 332 Y chromosomes from Romani populations across Europe, 814 Y-chromosomes from non-Romani host populations living in Southeastern, Southern and Eastern Europe as well as with 1680 Y-chromosomes from South Asian populations. The Bayash in Croatia represent one population of largely shared paternal genetic history characterized by substantial percentage (44%) of common H1-M82 and E3b1-M78 lineages. Relatively ancient expansion signals and limited diversity of Indian specific H1-M82 lineages imply descent from closely related paternal ancestors who could have been settled in the Indian subcontinent between 7th and 9th centuries AD. Minimal time divergence of the Bayash subpopulations is consistent with their putative migratory split within Romania towards Wallachia and Transilvania. Substantial percentage of E3b1 lineages and high associated microsatellite variance in the Bayash men is a reflection of significant admixture with majority populations from the Vardar-Morava-Danube catchment basin - possibly a common paternal signature of Romani populations in Southeastern Europe. Additional traces of admixture are evident in the modest presence of typical European haplogroups.

Are the Moravian Valachs of Czech Republic the Aromuns of Central Europe? Model population for isolation and admixture

E. Ehler1,2, V. Vančata2; 1Department of Anthropology and Human Genetics, Charles University in Prague, Faculty of Science, Prague, Czech Republic, 2Department of Biology and Ecological Education, Charles University in Prague, Faculty of Education, Prague, Czech Republic.

Presentation Number: P07.129

Moravian Valachs of Czech Republic are one of the most distinct ethnic groups from Central Europe. Related to similar populations in Poland and Slovakia, they emerge at the end of 15th century, as the north-westernmost prominence of migration that started 250 years earlier in northern Romania. Being predominately highland sheep herders and of putative Romanian origin, they represent a Central European analogue of Balkan Aromanian populations. We have gathered Y-chromosomal, linguistic, ethnographic and historical data for this population and compared them with surrounding as well as with east European populations. Linguistic data show specific parts of shared vocabulary of Romanian origin between several pastoral groups in Central and Eastern Europe. Comparing genetic and linguistic pairwise distance matrices (Mantel test) in these populations did not revealed any significant correlation. Thus we confirmed that plain geographical distance still plays the major role in genetic distances between populations in Europe. From our further analysis it is clear, that the Moravian Valachs, after at least five centuries of admixture, are not overly genetically different from surrounding populations. On the other hand, from the point of view of intra-population diversity, they are much more similar to isolated Balkan populations (e.g. Aromuns) than to Central European populations.

Phylogeography of the human Y chromosome haplogroup E3a

F. Cruciani1, B. Trombetta1, D. Sellitto2, C. Nodale1, R. Scozzari1; 1Sapienza Università di Roma, Rome, Italy, 2Consiglio Nazionale delle Ricerche, Rome, Italy.

Presentation Number: P07.134

The Y chromosome specific biallelic marker DYS271 defines the most common haplogroup (E3a) currently found in sub-Saharan Africa. A sister clade, E3b (E-M215), is rare in sub-Saharan Africa, but very common in northern and eastern Africa. On the whole, these two clades represent more than 70% of the Y chromosomes of the African continent. A third clade belonging to E3 (E3c or E-M329) has been recently reported to be present only in eastern Africa, at low frequencies. In this study we analyzed more than 1,600 Y chromosomes from 55 African populations, using both new and previously described biallelic markers, in order to refine the phylogeny and the geographic distribution of the E3a haplogroup. The most common E-DYS271 sub-clades (E-DYS271*, E-M191, E-U209) showed a non uniform distribution across sub-Saharan Africa. Most of the E-DYS271 chromosomes found in northern and western Africa belong to the paragroup E-DYS271*, which is rare in central and southern Africa. In these latter regions, haplogroups E-M191 and E-U209 show similar frequency distributions and coalescence ages (13 and 11 kyr, respectively), suggesting their involvement in the same migratory event/s. By the use of two new phylogenetically equivalent markers (V38 and V89), the earlier tripartite structure of E3 haplogroup was resolved in favor of a common ancestor for haplogroups E-DYS271 (formerly E3a) and E-M329 (formerly E3c). The new topology of the E3 haplogroup is suggestive of a relatively recent eastern African origin for the majority of the chromosomes presently found in sub-Saharan Africa.

Y-chromosome lineages in Xhosa and Zulu Bantu speaking populations

R. P. A. Gonçalves, H. Spínola, A. Brehm; Human Genetics Laboratory, Funchal, Portugal.

Presentation Number: P07.137

Y-chromosome Single Nucleotide Polymorphisms have been analysed in Zulu and Xhosa, two southern Africa Bantu speaking populations. These two ethnic groups have their origin on the farmer’s Bantu expansion from Niger-Congo border towards sub-Sahel regions on the southern tip of the continent, during the past 3000 years. Seven different Y-chromosome haplogroups were found in Zulu contrasting with only two in Xhosa. E3a, a common haplogroup among West sub-Saharans associated to Bantu migration was the most prevalent in both populations (56.9% in Zulu and 90% in Xhosa). The second most common haplogroup was E2 (29.3% in Zulu and 10% in Xhosa), present both in West and East African populations. The present-day Zulu and Xhosa paternal legacy is essentially of West sub-Saharan origin. Zulu population shows a most diverse genetic influence comparing to Xhosa, revealing some pre-Bantu expansion markers and East African influences. Zulu presents 8.6% Y-chromosome haplogroups (A, B, J1) of non-Bantu influence that could indicate gene flow from other populations, particularly Khoisan.

Human genetic population structure: Patterns and underlying processes

Presentation Time: Tuesday, 9:15 a.m. - 9:45 a.m.

G. Barbujani; University of Ferrara, Department of Biology and Evolution, Ferrara, Italy.

Presentation Number: S15.2

Classical studies of genetic diversity in humans consistently showed that the largest proportion of human diversity occurs among members of the same population. On average, differences among different populations in the same continent represent 5% of the global human variance, and differences among continents another 10%. Genetic variation is largely discordant across the genome, meaning that different loci show different spatial patterns, and implying that a good description of population structure can only be based on the analysis of multiple loci. Studies of single loci are also unlikely to reasonably identify an individual’s place of origin. A general decline of genetic of genetic diversity with distance from Africa, and a parallel increase in linkage disequilibrium, can be accounted for by the effects of a series of founder effects accompanying the spread of anatomically-modern humans from Africa. Recent DNA analyses at the global level show that most allelic variants are cosmopolitan and only a small percentage are continent-specific, whereas a clearer continental structure emerges when considering composite haplotypes. This suggests that, at the global level, gene flow has had a strong impact on genetic diversity, through both directional dispersal and successive short-range migratory exchanges. At the local level, several factors have contributed to genetic differentiation, and, in particular, language barriers have been shown to be associated with small but non-negligible increases of the genetic differences between neighboring populations.

Hierarchical analysis of 28 Y-chromosome SNP’s in the population of the Republic of Macedonia

P. Noveski, S. Trivodalieva, G. D. Efremov, D. Plaseska-Karanfilska;
Macedonian Academy of Sciences and Arts, Research Centre for Genetic Engineering and Biotechnology, Skopje, Macedonia, The Former Yugoslav Republic of.

Presentation Number: P05.211

Analysis of Y-chromosome haplogroups, defined by single nucleotide polymorphisms (SNP’s), has become a standard approach for studying the origin of human populations and measuring the variability among them. Furthermore, Y-SNP’s represent a new forensic tool, because their population specificity may allow to determine the origin of any male sample of interest for forensic purposes. The aim of this study was to develop a strategy for rapid, simple and inexpensive Y-chromosome SNP’s typing in the population of R. Macedonia. We have studied a total of 343 DNA male samples; 211 Macedonians, 111 Albanians and 21 of other ethnic origin (Roma, Serbs and Turks). Methodology included multiplex PCR and single nucleotide extension reaction by SNaPshot multiplex kit. The set of 28 markers has been grouped in 5 multiplexes in order to determine the most frequent haplogroups using only 1 or 2 multiplexes. Twenty different Y haplogroups were determined among 343 male DNA samples. The finding that five haplogroups (E3b1, I1b1, J2b1a, R1a and R1b) comprise more than 70% of the Y chromosomes is consistent with the typical European Y chromosome gene pool. The distribution of the Y-haplogroups differs between Macedonians and Albanians. The most common Y haplogroup among Macedonians is I1b1 (27.5%), followed by three haplogroups present with similar frequencies E3b1 (15.6%), R1a (14.2%) and R1b (11.4%). Among Albanians the most frequent Y haplogroup is E3b1 (28.8%), followed by R1b (18.0%), J2b1a (13.5%) and R1a (12.6%).

The following paper (probably) refers to a recent study, according to which:

One of the most elevated values of 35delG prevalence corresponds to Greece (1/28); the pattern of various 35delG prevalences is interpretated in the present meta-analysis as the result of Ancient Greek colonizations of the "Magna Grecia" in historical times.

Strong linkage disequilibrium for the frequent GJB2 35delG mutation in the Greek population
H. Kokotas¹, L. Van Laer², M. Grigoriadou¹, V. Iliadou³, J. Economides⁴, S. Pomoni¹, A. Pampanos¹, N. Eleftheriades⁵, E. Ferekidou⁶, S. Korres⁶, A. Giannoulia-Karantana⁷, G. Van Camp², M. B. Petersen¹;
¹Institute of Child Health, Athens, Greece, ²University of Antwerp, Antwerp, Belgium, ³AHEPA Hospital, Thessaloniki, Greece, ⁴‘Aghia Sophia’ Children’s Hospital, Athens, Greece, ⁵St. Loukas Hospital, Thessaloniki, Greece, ⁶Athens University, Athens, Greece, ⁷Athens University Medical School, Athens, Greece.

Presentation Number: P06.080

Approximately one in 1,000 children is affected by severe or profound hearing loss at birth or during early childhood (prelingual deafness). Up to forty percent of autosomal recessive, congenital, severe to profound hearing impairment cases result from mutations in a single gene, GJB2. The 35delG mutation accounts for the majority of GJB2 mutations detected in Caucasian populations and represents one of the most frequent disease mutations identified so far. Some previous studies have assumed that the high frequency of the 35delG mutation reflects the presence of a mutational hot spot, whilst other studies support the theory of a common founder. Greece is amongst the countries presenting high frequency of the 35delG mutation (3.5%), and a recent study raised the hypothesis of the origin of this mutation in ancient Greece. We genotyped 60 Greek deafness patients homozygous for the 35delG mutation for six single nucleotide polymorphisms (SNPs) and two microsatellite markers, mapping within or flanking the GJB2 gene, as compared to 60 Greek hearing controls. A strong linkage disequilibrium was found between the 35delG mutation and markers inside or flanking the GJB2 gene, at distances of 34 kb on the centromeric and 90 kb on the telomeric side of the gene, respectively. Our study supports the hypothesis of a founder effect and we further propose that ethnic groups of Greek ancestry could have propagated the 35delG mutation, as evidenced by historical data beginning from the 15^th century BC.

Hair/Skin color and Hair Length and Female Attractiveness in

Scand J Psychol. 2008 Apr 28 [Epub ahead of print]

The influence of skin tone, hair length, and hair colour on ratings of women's physical attractiveness, health and fertility.

Swami V, Furnham A, Joshi K.

The present study investigated the role of skin tone, hair colour and hair length in perceptions of women's physical attractiveness, health and fertility. One-hundred and thirty men and 112 women rated a series of 12 line drawings that varied in three levels of skin tone, two levels of hair colour and two levels of hair length. Results showed a number of interactions between the three variables, suggesting that these phenotypes are highly intercorrelated. However, there were also significant main effects of each of the variables, with hair colour generally explaining the greatest amount of variance. In general, light-toned figures were rated the most positively. Contrary to expectations, however, brunettes were rated more positively than blondes, and hair length had only a weak effect on ratings of attractiveness. Implications of these findings and the limitations of the use of line drawings are discussed in conclusion.

Link

Grandmothers' longevity negatively affects daughters' fertility

American Journal of Physical Anthropology (early view)

Grandmothers' longevity negatively affects daughters' fertility

Lorena Madrigal, Mauricio Meléndez-Obando

Abstract

The evolution of postmenopausal longevity in human females has been the subject of debate. Specifically, there is disagreement about whether the evolution of the trait should be understood as an adaptive or a neutral process, and if the former, what the selective mechanism is. There are two main adaptive proposals to explain the evolution of postreproductive longevity: the grandmother and the mother hypotheses. The grandmother hypothesis proposes that postreproductive longevity evolved because it is selectively advantageous for females to stop reproducing and to help raise their grandchildren. The mother hypothesis states that postmenopausal longevity evolved because it is advantageous for women to cease reproduction and concentrate their resources and energy in raising the children already produced. In this article, we test the mother and the grandmother hypotheses with a historical data set from which we bootstrapped random samples of women from different families who lived from the 1500s to the 1900s in the central valley of Costa Rica. We also compute the heritability of longevity, which allows us to determine if genes involved in longevity are nearly fixed in this population. Here we show that although longevity positively affects a woman's fertility, it negatively affects her daughter's fertility; for this reason, the heritability of longevity is unexpectedly high. Our data provide strong grounds for questioning the universality of the grandmother hypothesis and for supporting the mother hypothesis as a likely explanation for the evolution of human postreproductive longevity.

Link

Third cousin marriage and maximum fertility

John Hawks and Steve Sailer discuss a new Science paper (Agnar Helgason et al., "An Association Between the Kinship and Fertility of Human Couples", Science 8 February 2008: Vol. 319. no. 5864, pp. 813 - 816) on the correlation between fertility and degree of kinship in Iceland. From the public release about the paper:

In a paper published today deCODE scientists establish a substantial and consistent positive correlation between the kinship of couples and the number of children and grandchildren they have. The study, which analyzes more than 200 years of deCODE’s comprehensive genalogical data on the population of Iceland, shows that couples related at the level of third cousins have the greatest number of offspring.

It is of course clear why close relatives (closer than 3rd cousins) should have fewer children: this is due to the well known phenomenon of inbreeding depression. However, why should fertility increase up to a certain degree of kinship (~3rd cousins) and decrease after that?

One explanation is that there is some biological factor which decreases fitness as genetic dissimilarity increases. Perhaps more distantly related genomes don't "mesh" that well.

I suggest that the phenomenon could be partially explained by the fact that as kinship decreases, the age distribution of potential marriage partners becomes more varied.

A man's age difference from his sister is constrained by the fact that one's mother has a limited reproductive age range. In other words, one's sister is usually a few years older or younger than oneself, and rarely much older or younger.

But, if we look at first or second cousins, this difference increases. Your uncle or aunt is younger or older than your parents, and correspondingly their children can be more different than you in age.

As kinship decreases, your n-degree cousins become less constrained to be close to you in age. They could be much much older (if they are descended from short branches of one's family tree), or much much younger (if they are descended from long ones).

Of course, men usually marry women who are not that different from them in age (see data for Norway). But, the opportunity to marry someone much younger (or much older) than oneself is greater as kinship decreases.

It would be interesting to see data on average age differences correlated with degree of kinship in Iceland. If it turns out that, say, third-cousin marriage partners are less different in age than fourth-cousin partners, then an alternative explanation may be behind the observed fertility curve: age difference among spouses is negatively correlated with fertility.

Culture and ratings of attractiveness of different body shapes

Evolution and Human Behavior
Volume 27, Issue 6 , November 2006, Pages 443-456

Changing perceptions of attractiveness as observers are exposed to a different culture

Martin J. Tovée et al.

Abstract

It has been suggested that certain physical cues can be used to predict mate quality and that sensitivity to these cues would therefore be adaptive. From this, it follows that in environments where the optimal values for these features differ, the attractiveness preferences should also be different. In this study, we show that there are striking differences in attractiveness preferences for female bodies between United Kingdom (UK) Caucasian and South African Zulu observers. These differences can be explained by different local optima for survival and reproduction in the two environments. In the UK, a high body mass is correlated with low health and low fertility, and the converse is true in rural South Africa. We also report significant changes in the attractiveness preferences of Zulus who have moved to the UK. This suggests that these preferences are malleable and can change with exposure to different environments and conditions. Additionally, we show that Britons of African origin, who were born and who grew up in the UK, have exactly the same preferences as our UK Caucasian observers. These results suggest that humans have mechanisms for acquiring norms of attractiveness that are highly plastic, which allow them to track different ecological conditions through learning.

Link

Mother's mitochondrial curse

Trends Ecol Evol. 2004 May;19(5):238-44.

Mother's curse: the effect of mtDNA on individual fitness and population viability.

Gemmell NJ, Metcalf VJ, Allendorf FW.

The mitochondrial genome is considered generally to be an innocent bystander in adaptive evolution; however, there is increasing evidence that mitochondrial DNA (mtDNA) is an important contributor to viability and fecundity. Some of this evidence is now well documented, with mtDNA mutations having been shown to play a causal role in degenerative diseases, ageing, and cancer. However, most research on mtDNA has ignored the possibility that other instances exist where mtDNA mutations could have profound fitness consequences. Recent work in humans and other species now indicates that mtDNA mutations play an important role in sperm function, male fertility, and male fitness. Ironically, deleterious mtDNA mutations that affect only males, such as those that impair sperm function, will not be subject to natural selection because mitochondria are generally maternally inherited and could reach high frequencies in populations if the mutations are not disadvantageous in females. Here, we review how such mtDNA mutations might affect the viability of natural populations. We consider factors that increase or decrease the strength of the effect of mtDNA mutations on population viability and discuss what mechanisms exist to mitigate deleterious mtDNA effects.

Link

Origin of Maori and Polynesians

Interesting paper on Maori origins. The "slow boat" model referred to in the abstract is explained as follows:

A third model, the "slow boat" model (Richards et al. 1998; Lum and Cann 1998, 2000; Oppenheimer and Richards 2001a, 2001b), combines elements from the other two models, allowing genetic input into the ancestors of Polynesians from both "Melanesian" Papuan speakers (after the entangled bank model) and Austronesian speakers from east and southeast Asia (express train model). In addition, it attributes the general origin of the expansion to somewhere within island Southeast Asia and does not rule out Taiwan.

Human Biology 77.2 (2005) 157-177

Human Evolution in Polynesia

Adele L. H. Whyte et al.

Abstract

The number of eastern Polynesian females required to found the Māori population of Aotearoa (New Zealand) has been recalculated. Our estimates use computer simulations that incorporate realistic sigmoid population growth models and include previously published and new mitochondrial DNA (mtDNA) 3' hypervariable region 1 sequences from Māori (N = 109) and other eastern Polynesian (N = 125) volunteers. Approximately 190 (170–230) women are estimated to have been present in the founding waka (canoes). This new figure is more than double the previous estimate (Murray-McIntosh et al. 1998). Our claim for a large Māori founding population fits well with Māori oral history and has additional support from Māori paleodemography studies based on fertility estimates (Brewis et al. 1990; Pool 1991). An increasing body of data, including our own, supports the concept of planned multiple settlement voyages to Aotearoa by Polynesian navigators, leading us to suggest that theories for an "accidental discovery" of Aotearoa can now be completely disregarded. Four rare and novel Māori mtDNA haplotypes have been identified in the present study, but we are unable to assign the immediate origin of Māori to an exact Pacific island "homeland" because these haplotypes are not currently known elsewhere in Polynesia. We also discuss briefly the ultimate origin of all Polynesians (including Māori) in a wider context. In general, we support the emerging consensus for Pacific origins most closely encapsulated by the "slow boat" model (Oppenheimer and Richards 2001a). Previously "competing" models for the settlement of Oceania are seen as extremes in a continuum of possibilities with the slow boat representing an "intermediate" model. We suggest that a complete account is now close, incorporating data from all relevant interdisciplinary fields to provide a "synthetic total evidence theory."

Link

Azoospermia and Y chromosome haplogroups

Hum Reprod Update. 2005 May 12; [Epub ahead of print]

AZF deletions and Y chromosomal haplogroups: history and update based on sequence.

Vogt P.

AZF deletions are genomic deletions in the euchromatic part of the long arm of the human Y chromosome (Yq11) associated with azoospermia or severe oligozoospermia. Consequently, it can be assumed that these deletions remove Y chromosomal genes required for spermatogenesis. However, these 'classical' or 'complete' AZF deletions, AZFa, AZFb and AZFc, represent only a subset of rearrangements in Yq11. With the benefit of the Y chromosome sequence, more rearrangements (deletions, duplications, inversions) inside and outside the classical AZF deletion intervals have been elucidated and intra-chromosomal non-allelic homologous recombinations (NAHRs) of repetitive sequence blocks have been identified as their major cause. These include duplications in AZFa, AZFb and AZFc and the partial AZFb and AZFc deletions of which some were summarized under the pseudonym 'gr/gr' deletions. At least some of these rearrangements are associated with distinct Y chromosomal haplogroups and are present with similar frequencies in fertile and infertile men. This suggests a functional redundancy of the AZFb/AZFc multi-copy genes. Alternatively, the functional contribution(s) of these genes to human spermatogenesis might be different in men of different Y haplogroups. That raises the question whether, the frequency of Y haplogroups with different AZF gene contents in distinct human populations leads to a male fertility status that varies between populations or whether, the presence of the multiple Y haplogroups implies a balancing selection via genomic deletion/amplification mechanisms.

Link (pdf)

3-million year old polymorphism in Europeans

A new study in Nature Genetics by a group of Icelandic scientists has found a 900kbp inversion whose origin appears to be 3 million years before present, i.e., during the time that Homo erectus existed on earth, or even before that time. The mutation is found in Caucasoids (~20%) almost absent in Mongoloids, and rare in Negroids. The authors also discovered that the presence of the mutation has an effect on women having more children and higher recombination rates [the two have been found to be related].

The presence of such an ancient mutation is still a mystery, but two alternative explanations are proposed. The first one is that the polymorphism has been maintained in the human gene pool through balancing selection, which would indicate that its fitness benefits in heterozygotes might have corresponding fitness costs in homozygotes, which remain to be discovered. Since the polymorphism is more frequent in Europeans, it may be the case that there is something in the European environment which allows the fitness benefit to manifest itself, similar to the malarial environments in many places of the world which allow sickle-cell alleles to persist.

The second explanation -which is more likely in my opinion- is that ancestral Caucasoids underwent admixture with a different type of hominin which survived in Western Eurasia and which partially interbred with incoming modern sapiens humans. The mutation subsequently may have spread in the Caucasoid population by balancing selection (since it has not been fixed), and its absence in other populations may indicate simply that they did not interbreed with the different type of hominin.

As far as we know, during the radiation of anatomically modern Homo sapiens, the only candidate species for hybridization with it would be Homo neandertalensis. It's possible then that this was the source of the mutation in question, but since Neanderthals are also a relatively young species (less than 1 million years old) it may be the case that they also received it from a previous hominin species.

After the contested Flores hominin and the recent discovery of possible hybridization of Mongoloids with Homo erectus, this new study presents a new mystery about the origin of modern humans. It remains to be seen how these developments will eventually affect the current picture about human origins which insists on a recent African origin for our species. mtDNA research on humans and Neanderthals suggests no significant hybridization between the two species, and the arguments of the multiregionalists have been severely criticized, but I suspect that in the end the Out-of-Africa theory will have to accommodate the presence of (at least limited) admixture from older forms of Homo in the origins of modern humankind.

For more info Genes Promoting Fertility Are Found in Europeans, Scientists Find Effect of Natural Selection on Human Genome, Gene Arrangement Makes Some Europeans More Fertile.

Nature Genetics (published online)

A common inversion under selection in Europeans

Hreinn Stefansson et al.

A refined physical map of chromosome 17q21.31 uncovered a 900-kb inversion polymorphism. Chromosomes with the inverted segment in different orientations represent two distinct lineages, H1 and H2, that have diverged for as much as 3 million years and show no evidence of having recombined. The H2 lineage is rare in Africans, almost absent in East Asians but found at a frequency of 20% in Europeans, in whom the haplotype structure is indicative of a history of positive selection. Here we show that the H2 lineage is undergoing positive selection in the Icelandic population, such that carrier females have more children and have higher recombination rates than noncarriers.

Link

Greek genes into Australia

From Greece with love, the gift of life

Classified ads in the newspaper Sydney's Child are saturated with couples appealing for an "angel" to help them have a family. Couples can go to the US, where it is legal to pay donors, but the cost can be up to $US25,000. But pro-family cultural attitudes in Greece mean a higher proportion of women there are happy to give eggs at the same time as their own treatment, said Denyse Asher, an IVF scientist from the Sydney fertility service that put the McAdams in touch with their Greek doctors.

Ms Asher said it was rare for older women to find a donor from their immediate circle. "If they're younger, their sisters and cousins are all in the same reproductive age group. But if they find themselves sitting here at 44, most of their friends and sisters are too."

Besides, taking an egg from a known person can raise complex issues. "You've got to work out what role they will have. Are they going to want to be at birthday parties and how do you feel about that?" said Ms Asher, who runs a Bondi Junction fertility service with her husband, Joel Bernstein.

She said they had referred more than 50 couples to the Greek clinic, of whom 76 per cent had become pregnant.

Link

Beautiful wives and gay sons

Jeet at Gene Expression links to a new study which discovers that female relatives of the mothers of male homosexuals produce more offspring. Thus a particular genetic predisposition manifests itself as homosexuality in a man and as increased fertility in a woman. Homosexuality is due to gene(s) which are (obviously) detrimental to a man's genetic fitness but are advantageous for his female relatives.

This would agree with my recent idea that a person's sexual orientation is a combination of masculinity/femininity genetic factors inherited from his/her parents.

Male homosexuals would thus tend to have more feminine parents. A more feminine mother would give birth to more children, both because she would be more attractive, and thus likely to be married early, but also because femininity is probably a good indication of a woman's reproductive health.

If this intuition is correct, then in layman's terms, if your wife's female relatives have big families, then on the up side there's an increased chance that you have a beautiful and fertile wife, but on the down side there is an increased chance that your son will be gay.