Wednesday, December 12, 2012 9:36:40 PM
Researchers: Interbreeding may have been underestimated in the human fossil record
[ http://www.livescience.com/25361-monkeys-show-why-it-s-hard-to-prove-ancient-human-interbreeding.html ]
James Fluere | Saturday, December 08, 2012
Researchers at the University of Michigan have learned more about the role of interbreeding in human evolution. According [ http://www.ns.umich.edu/new/multimedia/slideshows/21025-monkey-business-what-howler-monkeys-can-tell-us-about-the-role-of-interbreeding-in-human-evolution ] to U-M, researchers have spent years trying to answer a rather complex question: Did different species of early humans interbreed and produce offspring of mixed ancestry? Unfortunately, answering this question is not a straight forward or easy process.
Geneticists believe, based on recent studies, that Neanderthals may have had sex with modern humans tens of thousands of years ago in the Middle East, adding to the modern human gene pool. According [ http://www.livescience.com/25361-monkeys-show-why-it-s-hard-to-prove-ancient-human-interbreeding.html ] to LiveScience, when scientists finished sequencing the Neanderthal genome in 2010, they announced that some modern humans’ DNA came from the early humans.
This discovery, however, is not universally accepted, and the fossil record has not helped to make clear the role of interbreeding or hybridization in human evolution.
U-M researchers are confident that they may have discovered why it is so hard to confirm cases of interbreeding among primates and early humans by relying solely on fossil remains. They made this discovery while examining cases of interbreeding between two species of modern-day howler monkeys in Mexico. Their conclusions are based on analyses of genetic and morphological data gathered from live-captured monkeys over the past ten years.
Researchers studied mantled howler monkeys and black howler monkeys (two primate species that diverged approximately 3 million years ago). The two species of modern-day howler monkeys are different when it comes to behavior, appearance and the number of chromosomes they have. Besides the state of Tabasco in southeastern Mexico, each species lives in a different geographical region. In Tabasco, however, the two species live together and interbreed in what researchers call a hybrid zone.
The researchers discovered that individuals of mixed ancestry who share most of their genome with one of the two species are physically indistinguishable from the pure individuals of that species.
“The implications of these results are that physical features are not always reliable for identifying individuals of hybrid ancestry. Therefore, it is possible that hybridization has been underestimated in the human fossil record,” said Liliana Cortés-Ortiz, an evolutionary biologist and primatologist and an assistant research scientist at the U-M Department of Ecology and Evolutionary Biology and the Museum of Zoology, in a statement.
For many years, anthropologists have tried to identify interbreeding among human ancestral species based on the fossil record. They have come to the conclusion that hybridization is extremely rare, according to the U-M researchers. The howler monkey study, however, “suggests that the lack of strong evidence for hybridization in the fossil record does not negate the role it could have played in shaping early human lineage diversity,” said Mary Kelaita, a postdoctoral fellow at the University of Texas at San Antonio’s Department of Anthropology.
In the future, researchers argue, studies should revisit and more fully investigate the process of interbreeding, the factors determining the appearance of morphology in hybrid individuals and the magnitude of reproductive isolation between species.
The researchers examined various types of genetic markers to trace the ancestry of each howler monkey they live-captured. Molecular markers helped researchers determine the relative genetic contributions of the parental species to each hybrid.
The researchers concluded that the 128 hybrid individuals they found were likely the result of several generations of hybridization or sex between hybrids and pure individuals.
They also conducted statistical analyses on body measurements and discovered a lot of morphological variation in individuals of mixed ancestry. Researchers found that when individuals were classified based on the amount of their genome they shared with each parent species, it was clear that individuals of mixed ancestry that shared a large portion of their genome with one of the species were physically indistinguishable from the pure individuals of that species.
Researchers examined 135 adult howler monkeys from Tabasco and 76 others from Veracruz, Campeche, Chiapas, the Quintana Roo states in Mexico and Peten in Guatemala. They gathered blood, hair and morphometric measurements from the monkeys before releasing them in the locations they were captured. In addition to obtaining the animals’ weight, 16 body-part measurements were taken, including trunk, tail, leg, foot, arm and hand length.
The study’s findings were recently described in detail in the American Journal of Physical Anthropology.
© Science Recorder News
http://www.sciencerecorder.com/news/researchers-interbreeding-may-have-been-underestimated-in-the-human-fossil-record/ [with comments]
*
Morphological variation of genetically confirmed Alouatta Pigra × A. palliata hybrids from a natural hybrid zone in Tabasco, Mexico
7 DEC 2012
http://onlinelibrary.wiley.com/doi/10.1002/ajpa.22196/abstract
===
Cavemen Were Better at Depicting Quadruped Walking than Modern Artists: Erroneous Walking Illustrations in the Fine Arts from Prehistory to Today
December 5, 2012
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0049786 [via http://www.livescience.com/25269-cavemen-better-modern-artists-animal-walks.html (with comments)]
===
Genetic Sequencing Traces Gypsies Back to Ancient Indian Origin
Romani wagon in Germany, 1930s.
Image courtesy of Wikimedia Commons/Allgemeiner Deutscher Nachrichtendienst - Zentralbild (Bild 183)
By Katherine Harmon | December 6, 2012
The Romani people—once known as “gypsies” or Roma—have been objects of both curiosity and persecution [ http://www.scientificamerican.com/article.cfm?id=genome-test-slammed-assessing-racial-purity ] for centuries. Today, some 11 million Romani, with a variety of cultures, languages and lifestyles, live in Europe—and beyond. But where did they come from?
Earlier studies of their language [ http://www.scientificamerican.com/article.cfm?id=disease-maps-pinpoint-origin-of-indo-european-languages ] and cursory analysis of genetic patterns pinpointed India as the group’s place of origin [ http://blogs.scientificamerican.com/observations/2010/05/14/genetic-ancestry-testing-is-an-inexact-science-task-force-says/ ] and a later influence of Middle Eastern and Central Asian linguistics. But a new study uses genome-wide sequencing [ http://www.scientificamerican.com/article.cfm?id=environmental-factors-diabetes ] to point to a single group’s departure from northwestern Indian some 1,500 years ago and has also revealed various subsequent population changes as the population spread throughout Europe.
“Understanding the Romani’s genetic legacy is necessary to complete the genetic characterization of Europeans as a whole, with implications for various fields, from human evolution to the health sciences,” said Manfred Kayser, of Erasmus University in Rotterdam and paper co-author, in a prepared statement.
To begin the study, a team of European researchers collected data on some 800,000 genetic variants (single nucleotides polymorphisms) in 152 Romani people from 13 different Romani groups in Europe. The team then contrasted the Romani sequences with those already known for more than 4,500 Europeans as well as samples from the Indian subcontinent, Central Asia and the Middle East.
According to the analysis, the initial founding group of Romani likely departed from what is now the Punjab state in northwestern India close to the year 500 CE. From there, they likely traveled through Central Asia and the Middle East but appear to have mingled only moderately with local populations there. The subsequent doorway to Europe seems to have been the Balkan area—specifically Bulgaria—from which the Romani began dispersing around 1,100 CE.
These travels, however, were not always easy. For example, after the initial group left India, their numbers took a dive, with less than half of the population surviving (some 47 percent, according to the genetic analysis). And once groups of Romani that would go on to settle Western Europe left the Balkan region, they suffered another population bottleneck, losing some 30 percent of their population. The findings [ http://www.cell.com/current-biology/abstract/S0960-9822(12)01260-2 ] were published online December 6 in Current Biology.
The researchers were also able to examine the dynamics of various Romani populations as they established themselves in different parts of Europe. The defined geographic enclaves appear to have remained largely isolated from other populations of European Romani over recent centuries. And the Romani show more evidence of marriage among blood relatives than do Indians or non-Romani Europeans in the analysis.
But the Romani did not always keep to themselves. As they moved through Europe and set up settlements, they invariably met—and paired off with—local [ http://www.scientificamerican.com/article.cfm?id=denisovan-genome ] Europeans. And some groups, such as the Welsh Romani, show a relatively high rate of bringing locals—and their genetics—into their families.
Local mixing was not constant over the past several centuries—even in the same groups. The genetic history, as told through this genome-wide analysis, reveals different social mores at different times. For example, Romani populations in Romania, Hungary, Slovakia, Bulgaria and Croatia show genetic patterns that suggest a limited pairing with local populations until recently. Whereas Romani populations in Portugal, Spain and Lithuania have genetic sequences that suggest they had previously mixed with local European populations more frequently but have “higher levels of recent genetic isolation from non-Romani Europeans,” the researchers noted in their paper.
The Romani have often been omitted from larger genetic studies, as many populations are still somewhat transient and/or do not participate in formal institutions such as government programs and banking. “They constitute an important fraction of the European population, but their marginalized situation in many countries also seems to have affected their visibility in scientific studies,” said David Comas, of the Institut de Biologia Evolutiva at the Universitat Pompeu Fabra in Spain and co-author of the new paper, in a prepared statement.
Finer genetic analysis of various Romani populations as well as those from the putative founder region of India will help establish more concrete population dynamics and possibly uncover new clues to social and cultural traditions in these groups that have not kept historical written records.
© 2012 Scientific American, a Division of Nature America, Inc.
http://blogs.scientificamerican.com/observations/2012/12/06/genetic-sequencing-traces-gypsies-back-to-ancient-indian-origin/ [with comments]
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[ http://www.livescience.com/25361-monkeys-show-why-it-s-hard-to-prove-ancient-human-interbreeding.html ]
James Fluere | Saturday, December 08, 2012
Researchers at the University of Michigan have learned more about the role of interbreeding in human evolution. According [ http://www.ns.umich.edu/new/multimedia/slideshows/21025-monkey-business-what-howler-monkeys-can-tell-us-about-the-role-of-interbreeding-in-human-evolution ] to U-M, researchers have spent years trying to answer a rather complex question: Did different species of early humans interbreed and produce offspring of mixed ancestry? Unfortunately, answering this question is not a straight forward or easy process.
Geneticists believe, based on recent studies, that Neanderthals may have had sex with modern humans tens of thousands of years ago in the Middle East, adding to the modern human gene pool. According [ http://www.livescience.com/25361-monkeys-show-why-it-s-hard-to-prove-ancient-human-interbreeding.html ] to LiveScience, when scientists finished sequencing the Neanderthal genome in 2010, they announced that some modern humans’ DNA came from the early humans.
This discovery, however, is not universally accepted, and the fossil record has not helped to make clear the role of interbreeding or hybridization in human evolution.
U-M researchers are confident that they may have discovered why it is so hard to confirm cases of interbreeding among primates and early humans by relying solely on fossil remains. They made this discovery while examining cases of interbreeding between two species of modern-day howler monkeys in Mexico. Their conclusions are based on analyses of genetic and morphological data gathered from live-captured monkeys over the past ten years.
Researchers studied mantled howler monkeys and black howler monkeys (two primate species that diverged approximately 3 million years ago). The two species of modern-day howler monkeys are different when it comes to behavior, appearance and the number of chromosomes they have. Besides the state of Tabasco in southeastern Mexico, each species lives in a different geographical region. In Tabasco, however, the two species live together and interbreed in what researchers call a hybrid zone.
The researchers discovered that individuals of mixed ancestry who share most of their genome with one of the two species are physically indistinguishable from the pure individuals of that species.
“The implications of these results are that physical features are not always reliable for identifying individuals of hybrid ancestry. Therefore, it is possible that hybridization has been underestimated in the human fossil record,” said Liliana Cortés-Ortiz, an evolutionary biologist and primatologist and an assistant research scientist at the U-M Department of Ecology and Evolutionary Biology and the Museum of Zoology, in a statement.
For many years, anthropologists have tried to identify interbreeding among human ancestral species based on the fossil record. They have come to the conclusion that hybridization is extremely rare, according to the U-M researchers. The howler monkey study, however, “suggests that the lack of strong evidence for hybridization in the fossil record does not negate the role it could have played in shaping early human lineage diversity,” said Mary Kelaita, a postdoctoral fellow at the University of Texas at San Antonio’s Department of Anthropology.
In the future, researchers argue, studies should revisit and more fully investigate the process of interbreeding, the factors determining the appearance of morphology in hybrid individuals and the magnitude of reproductive isolation between species.
The researchers examined various types of genetic markers to trace the ancestry of each howler monkey they live-captured. Molecular markers helped researchers determine the relative genetic contributions of the parental species to each hybrid.
The researchers concluded that the 128 hybrid individuals they found were likely the result of several generations of hybridization or sex between hybrids and pure individuals.
They also conducted statistical analyses on body measurements and discovered a lot of morphological variation in individuals of mixed ancestry. Researchers found that when individuals were classified based on the amount of their genome they shared with each parent species, it was clear that individuals of mixed ancestry that shared a large portion of their genome with one of the species were physically indistinguishable from the pure individuals of that species.
Researchers examined 135 adult howler monkeys from Tabasco and 76 others from Veracruz, Campeche, Chiapas, the Quintana Roo states in Mexico and Peten in Guatemala. They gathered blood, hair and morphometric measurements from the monkeys before releasing them in the locations they were captured. In addition to obtaining the animals’ weight, 16 body-part measurements were taken, including trunk, tail, leg, foot, arm and hand length.
The study’s findings were recently described in detail in the American Journal of Physical Anthropology.
© Science Recorder News
http://www.sciencerecorder.com/news/researchers-interbreeding-may-have-been-underestimated-in-the-human-fossil-record/ [with comments]
*
Morphological variation of genetically confirmed Alouatta Pigra × A. palliata hybrids from a natural hybrid zone in Tabasco, Mexico
7 DEC 2012
http://onlinelibrary.wiley.com/doi/10.1002/ajpa.22196/abstract
===
Cavemen Were Better at Depicting Quadruped Walking than Modern Artists: Erroneous Walking Illustrations in the Fine Arts from Prehistory to Today
December 5, 2012
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0049786 [via http://www.livescience.com/25269-cavemen-better-modern-artists-animal-walks.html (with comments)]
===
Genetic Sequencing Traces Gypsies Back to Ancient Indian Origin
Romani wagon in Germany, 1930s.
Image courtesy of Wikimedia Commons/Allgemeiner Deutscher Nachrichtendienst - Zentralbild (Bild 183)
By Katherine Harmon | December 6, 2012
The Romani people—once known as “gypsies” or Roma—have been objects of both curiosity and persecution [ http://www.scientificamerican.com/article.cfm?id=genome-test-slammed-assessing-racial-purity ] for centuries. Today, some 11 million Romani, with a variety of cultures, languages and lifestyles, live in Europe—and beyond. But where did they come from?
Earlier studies of their language [ http://www.scientificamerican.com/article.cfm?id=disease-maps-pinpoint-origin-of-indo-european-languages ] and cursory analysis of genetic patterns pinpointed India as the group’s place of origin [ http://blogs.scientificamerican.com/observations/2010/05/14/genetic-ancestry-testing-is-an-inexact-science-task-force-says/ ] and a later influence of Middle Eastern and Central Asian linguistics. But a new study uses genome-wide sequencing [ http://www.scientificamerican.com/article.cfm?id=environmental-factors-diabetes ] to point to a single group’s departure from northwestern Indian some 1,500 years ago and has also revealed various subsequent population changes as the population spread throughout Europe.
“Understanding the Romani’s genetic legacy is necessary to complete the genetic characterization of Europeans as a whole, with implications for various fields, from human evolution to the health sciences,” said Manfred Kayser, of Erasmus University in Rotterdam and paper co-author, in a prepared statement.
To begin the study, a team of European researchers collected data on some 800,000 genetic variants (single nucleotides polymorphisms) in 152 Romani people from 13 different Romani groups in Europe. The team then contrasted the Romani sequences with those already known for more than 4,500 Europeans as well as samples from the Indian subcontinent, Central Asia and the Middle East.
According to the analysis, the initial founding group of Romani likely departed from what is now the Punjab state in northwestern India close to the year 500 CE. From there, they likely traveled through Central Asia and the Middle East but appear to have mingled only moderately with local populations there. The subsequent doorway to Europe seems to have been the Balkan area—specifically Bulgaria—from which the Romani began dispersing around 1,100 CE.
These travels, however, were not always easy. For example, after the initial group left India, their numbers took a dive, with less than half of the population surviving (some 47 percent, according to the genetic analysis). And once groups of Romani that would go on to settle Western Europe left the Balkan region, they suffered another population bottleneck, losing some 30 percent of their population. The findings [ http://www.cell.com/current-biology/abstract/S0960-9822(12)01260-2 ] were published online December 6 in Current Biology.
The researchers were also able to examine the dynamics of various Romani populations as they established themselves in different parts of Europe. The defined geographic enclaves appear to have remained largely isolated from other populations of European Romani over recent centuries. And the Romani show more evidence of marriage among blood relatives than do Indians or non-Romani Europeans in the analysis.
But the Romani did not always keep to themselves. As they moved through Europe and set up settlements, they invariably met—and paired off with—local [ http://www.scientificamerican.com/article.cfm?id=denisovan-genome ] Europeans. And some groups, such as the Welsh Romani, show a relatively high rate of bringing locals—and their genetics—into their families.
Local mixing was not constant over the past several centuries—even in the same groups. The genetic history, as told through this genome-wide analysis, reveals different social mores at different times. For example, Romani populations in Romania, Hungary, Slovakia, Bulgaria and Croatia show genetic patterns that suggest a limited pairing with local populations until recently. Whereas Romani populations in Portugal, Spain and Lithuania have genetic sequences that suggest they had previously mixed with local European populations more frequently but have “higher levels of recent genetic isolation from non-Romani Europeans,” the researchers noted in their paper.
The Romani have often been omitted from larger genetic studies, as many populations are still somewhat transient and/or do not participate in formal institutions such as government programs and banking. “They constitute an important fraction of the European population, but their marginalized situation in many countries also seems to have affected their visibility in scientific studies,” said David Comas, of the Institut de Biologia Evolutiva at the Universitat Pompeu Fabra in Spain and co-author of the new paper, in a prepared statement.
Finer genetic analysis of various Romani populations as well as those from the putative founder region of India will help establish more concrete population dynamics and possibly uncover new clues to social and cultural traditions in these groups that have not kept historical written records.
© 2012 Scientific American, a Division of Nature America, Inc.
http://blogs.scientificamerican.com/observations/2012/12/06/genetic-sequencing-traces-gypsies-back-to-ancient-indian-origin/ [with comments]
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