探花直播 of Cambridge - 探花直播 of Tartu

Decline in the number of males involved in reproduction during the period of global growth

fpjl2 — Tue, 17 Mar 2015 17:55:11 +0000

In a study published recently in Genome Research, scientists from 探花直播 of Cambridge, Estonian Biocentre, 探花直播 of Tartu, Arizona State 探花直播 and 64 other institutions around the world discovered that accumulation of material culture during the middle and late stages of Neolithic, four to eight thousand years ago, is associated with a dramatic decline in genetic diversity in male lineages whereas female genetic diversity was on the rise.

It has been widely recognized that a major bottleneck, or decrease in genetic diversity, occurred approximately 50 thousand years ago when a subset of humans left Africa to colonize the rest of the world. Signatures of this bottleneck can be seen in most genes of non-African populations regardless of whether they are inherited from both parents or, as confirmed in this work, only along the father鈥檚 or mother鈥檚 genetic lines.

鈥淢ost surprisingly to us, we detected another, male-specific, bottleneck during the period of global growth. 探花直播signal for this bottleneck dates to a time period when humans in different parts of the world had already for thousands of years been sedentary farmers,鈥� said senior author Toomas Kivisild from the 探花直播 of Cambridge鈥檚 Division of Biological Anthropology.

View an infographic of the research story here.

Melissa Wilson-Sayers, one of the lead authors from the School of Life Sciences at Arizona State 探花直播, added: 鈥淚nstead of 鈥榮urvival of the fittest鈥� in biological sense, the accumulation of wealth and power may have increased the reproductive success of a limited number of socially 鈥榝it鈥� males and their sons.鈥�

探花直播researchers said studying genetic history is important for understanding underlying levels of genetic variation. Having a high level of genetic diversity is beneficial to humans for several reasons. First, when the genes of individuals in a population vary greatly, the group has a greater chance of thriving and surviving 鈥� particularly against disease. It may also reduce the likelihood of passing along unfavorable genetic traits, which can weaken a species over time.

According to Monika Karmin, co-author from 探花直播 of Tartu, their findings further stress the differences in human male and female genetic histories which also may have implications related to human health.

鈥� 探花直播striking difference in the number of reproductive males and females in that time window certainly affected the diversity of genes on the male genetic line,鈥� said Karmin. 鈥淲e know that some populations are predisposed to certain types of genetic disorders. Researchers worldwide are trying to figure out what the underlying genetic structure is, so now also the fact that the male part of human lineages has gone trough a severe bottleneck has to be considered.鈥�

鈥淲hen a doctor tries to provide a diagnosis when you are sick, you鈥檒l be asked about your environment, what鈥檚 going on, and your genetic history based on your family鈥檚 health. If we want to understand human health on a global scale, we need to know our global genetic history; that is what we are studying here,鈥� added Wilson-Sayers.

探花直播researchers believe this will be relevant for informing patterns of genetic diversity across whole human populations, including informing about susceptibility to diseases, independently in different populations.

Adapted from an Arizona State 探花直播 press release.

Wealth and power may have played a stronger role than 鈥渟urvival of the fittest鈥�.

Most surprisingly to us, we detected another, male-specific, bottleneck during the period of global growth

Toomas Kivisild

Arizona State 探花直播

Details from infographic produced by Arizona State 探花直播

探花直播text in this work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page. For image rights, please see the credits associated with each individual image.

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鈥楲ight skin鈥� gene mirrors socio-cultural boundaries in Indian population

fpjl2 — Wed, 13 Nov 2013 10:43:27 +0000

探花直播genetic mutation in SLC24A5 is known to be pivotal in the evolution of light skin, and is responsible for a significant part of the skin colour differences between Europeans and Africans.

Now, a new study has examined for the first time a large, uniform genetic sample collected directly in south India, and suggests that natural selection is not the sole factor in skin tone variation across the Indian sub-continent, and that cultural and linguistic traits still delineate this skin pigment genetic mutation.聽

探花直播results show that the gene is found with much higher frequency in Indo-European speaking groups that are more prevalent in the north-west of the country.

But the mutation is also high in populations groups known to have migrated north to south, such as the Saurashtrians, who - while native to Gujarat in north-west India - are now predominantly found in the Madurai district in its southernmost tip.

Researchers say that the study, published last week in the journal PLoS Genetics, shows that the genetic mutation in SLC24A5 has a common origin between Europeans and Indians.

But while the complete dominance of the gene in Europeans is likely to be solely down to natural selection, they say, the rich diversity of this genetic variant in India - high in some populations while non-existent in others, even neighbouring ones - has some correlation with factors of language, ancestral migration and distinct social practices such as limiting marriage partners to those with specific criteria.

探花直播researchers say the findings display an 鈥渋ntriguing interplay鈥� between natural selection and the 鈥渦nique history and structure鈥� of populations inhabiting the Indian subcontinent.聽聽聽聽聽聽聽聽聽

鈥淚n India, this genetic variant doesn鈥檛 just follow a 鈥榗lassical鈥� theory of natural selection - that it鈥檚 lower in the south where darker skin protects against fiercer sunlight,鈥� said study co-author Mircea Iliescu from Cambridge鈥檚 Biological Anthropology Division.

鈥� 探花直播distribution of the SLC24A5 genetic variant in India follows patterns very much influenced by population. Understanding the genetic architecture behind the remarkable skin colour variation found today in the populations of India has the potential to shed light on the wider mechanisms responsible for creating diversity throughout human evolution,鈥� Iliescu said.

In the 1950s it was proposed that there was a massive wave of European migration into northern India a few thousand years ago, described as the 鈥楢ryan invasion鈥�, which led to the collapse of the Harrapan Civilisation - a Bronze-Age Civilisation.

This theory, now considered widely discredited by many researchers due to the lack of archaeological evidence, is still a hugely debated issue in contemporary Indian politics - invoked by political parties in the southern states of India who claim that the southern populations, described by some as the 鈥楧ravidians鈥�, are the truly indigenous people of India.

探花直播researchers say that, while speculative, they find it 鈥渉ard to imagine鈥� a large-scale population migration at a single point in history based on this study 鈥� since the presence of this genetic mutation is too widespread, with an average frequency of 53%, including the Austroasiatic language groups thought to have originated in southeast Asia.

They say the wide variation and complex pattern hints at the possibility of multiple 鈥済ene flows鈥� into the sub-continent over a much longer period of time, some of which might be linked to the spread of agriculture; although the study does show higher frequencies of SLC24A5 in Indo-European speaking groups compared to so-called Dravidian populations.

探花直播researchers suggest that aspects of 鈥榮ocial selection鈥�, such as high levels of 鈥榚ndogamy鈥� - marriage within a particular group in accordance with custom - as a result of the caste system, has created a 鈥渕osaic pattern鈥� for this skin pigmentation mutation across Indian populations.

鈥淭his study helps us to understand various other mechanisms that could have contributed or shaped the existing biological spectrum of human skin colour besides natural selection - driven by ultraviolet rays - and further understanding of this complex phenotypic trait,鈥� said Chandana Basu Mallick, a co-author on the study from the 探花直播 of Tartu in Estonia.

鈥淲e are taking gradual steps towards understanding the evolutionary history of this adaptive trait, and the journey of our ancestors from fur to the diverse skin tones of the present day.鈥�

鈥淥ur work addresses human diversity, diversity which should be celebrated,鈥� added Iliescu. 鈥淚t tries to explain the origins and history of this diversity - opening up a window into a different kind of history, not just a history of places and objects, but a living history which helps us to better understand ourselves.鈥�

鈥淪tudies on Indian populations have been under-represented in the genomic era, and the understanding of Indian genetics is still at a very early stage. With this study, we hope we鈥檝e brought valuable new understanding to the evolutionary genetics of Indian populations.鈥�

Latest research shows that the presence of the genetic mutation for lighter skin - found in 鈥渁lmost 100%鈥� of Europeans - broadly conforms to many cultural and linguistic differences, as well as ancestral, in the wider Indian population.

In India, this genetic variant doesn鈥檛 just follow a 鈥榗lassical鈥� theory of natural selection

Mircea Iliescu

Prasanth Chandran

鈥淲here you are going is more important than how fast you are going鈥�

This work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page.

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