Post has attachment
How a supervolcano almost halted the human migration : Or did it? Genetics, Archaeology and physics are being used to figure out that happened.

What is Toba? Mt. Toba was a supervolcano which erupted around 75,000 years back. This was Earth's largest volcanic eruption in the past 2 million years.

Why does this matter? Toba drastically altered the world’s climate and caused a six-year-long volcanic winter in some parts of the world. Correlating the date of the eruption to evidence of a genetic bottleneck in the modern human population around the same time, some researchers suggested that populations of modern humans (Homo sapiens) that had previously expanded out of Africa were unable to cope with these changes, and thus experienced huge population declines everywhere except in tropical, mainly African, refuges.

Alternate routes Genetic and fossil evidence has accumulated in support of an African origin for modern humans. Despite this consensus, several questions remain with regard to the mode and timing of dispersal out of the continent. Competing models differ primarily by the number of dispersals, their geographic route, and the extent to which expanding modern humans interacted with other hominins.

Please note the pic is not Mt.Toba

References and links

http://www.sciencedirect.com/science/article/pii/S1040618215011891

http://www.pnas.org/content/110/26/10699.full

http://www.yourgenome.org/stories/evolution-of-modern-humans

http://www.geotimes.org/sept07/article.html?id=nn_eruption.html

https://en.wikipedia.org/wiki/Toba_catastrophe_theory
Photo
Add a comment...

Post has attachment
We are all related : Strange as this sounds, this is the outcome of a scientific search for the human migration using genetic markers. As genetic mutations were observed, the rarer of these were passed down from father to son (Y-chromosomal) and from mother to daughter (mtDNA). Tracing these back led to one tree for men and another for women. And the male line and female line do not converge. Though we are all descended from what is called Y-chromosomal Adam and mtDNA Eve, they did not live at the same time. I'm assuming the other lines just died out. The surprising conclusion? We are all related. We are genetically related.

Our common ancestors : Some 99% of the human genome is shuffled from one birth to the next. The Genographic Project traces the 1% of the genome which is not shuffled—mitochondrial DNA (mtDNA) through the maternal line and the Y-chromosome through the paternal. These jokers in the pack allow geneticists to work back to our common ancestors. Our mtDNA appears to coalesce in a single woman, who lived on the African savannah 150,000 years ago. Our Y-chromosome survives from a single man, who lived in the Rift Valley of Kenya or Tanzania 59,000 years ago. So Adam and Eve did exist—90,000 years apart. The discrepancy is because, unlike the biblical Adam and Eve, this couple only represent the last common Ancestors we can trace genetically.

African Roots : Different populations carry distinct genetic markers. Following the markers through the generations reveals a genetic tree on which today’s many diverse branches can be followed backward to their common African root. The markers still present in our genes allow us to chart ancient human migrations from Africa across the continents. Through these markers, we can see living evidence of an ancient trek to populate the globe.

How Neanderthal are you? : Everyone living outside of Africa today has a small amount of Neanderthal in them, carried as a living relic of these ancient encounters. A team of scientists comparing the full genomes of the two species concluded that most Europeans and Asians have between 1 to 4 percent Neanderthal DNA. Indigenous sub-Saharan Africans have no Neanderthal DNA because their ancestors did not migrate through Eurasia.

Thomas Jefferson was descended from the Middle East : Strange as this sounds, this can actual be proved from the genetic mutation his gene shows. You can read more about it here - http://www.sciencedaily.com/releases/2007/03/070328111115.htm

References and Links

Youtube link to Spencer Well's video : https://www.youtube.com/watch?v=-dDXIX-y6aY

http://www.monticello.org/site/research-and-collections/biographical-identifications

https://genographic.nationalgeographic.com/science-behind/

http://moreintelligentlife.com/content/jm-ledgard/exodus?page=full

https://genographic.nationalgeographic.com/neanderthal/

https://en.wikipedia.org/wiki/Mitochondrial_Eve

http://archiver.rootsweb.ancestry.com/th/read/GENEALOGY-DNA/2005-06/1119997289

Pic courtesy : Natgeo

#science #genetics  
Photo
Add a comment...

Post has attachment
Born To Swim? : This is a known mammalian response at an early age when babies are dunked in the water.... holding their breath, the heart slows down and blood is shifted away from the peripheral muscles to conserve oxygen for the brain and heart. It's the same reflex which is observed in some other mammals as well. Makes you wonder about our ancestry!

Article Extract: Just blow into a baby’s face and watch him or her gulp air, close eyes, and stop whatever they’re doing. Parents have used this as a way to get their little ones to stop crying – but it’s also the path to swimming.

The response is what’s known as the bradycardic reflex, which is part of the mammalian diving reflex. When the face of an infant is exposed to cold water, the heart slows down and blood is shifted away from the peripheral muscles to conserve oxygen for the brain and heart, and they typically hold their breath. The reflex is the same one that protects babies from getting milk in their lungs. “It’s interesting that the reflex kind of reroutes the entire circulatory system to save blood for the heart and brain, and not pump it through the rest of the body,” says Wennergren.

Wennergren had heard that after 6 months of age, this reflex fades away – so he decided to look into the function of the diving response in babies of different ages. Along with a graduate student, he studied 36 infants in swimming classes at warm pool – one of the few actual studies into diving babies. But the ability to hold breath doesn’t mean that babies can swim safely.

“In diving animals, the reflex persists for their whole life,” Wennergren told KinderLab, noting that adult humans also have the same reflex – if you dunk your face in cold water, you’ll gasp and hold your breath.

Article Link: http://www.popsci.com/blog-network/kinderlab/born-swim?dom=PSC&loc=recent&lnk=4&con=born-to-swim-

Linked Paper in PubMed: http://www.ncbi.nlm.nih.gov/pubmed/12022304

Must see: (Physiology of the Diving Reflex in Humans and Aquatic Aammals and Birds) http://www.bio.davidson.edu/people/midorcas/animalphysiology/websites/2011/haug/Index.htm

Wikipedia Link: http://en.wikipedia.org/wiki/Mammalian_diving_reflex

Video link from an old BBC video: The Diving Reflex - Infant Babies Swimming Underwater

Pic courtesy: Popsci main article link... Are baby humans natural-born swimmers? MasterFinally, via wikipedia

#science   #baby   #bradycardic   #reflex   
Photo
Add a comment...

Post has attachment
Genetics reveals how conquerors affect populations : I saw this once on a program on the genome project. Though, the cases were more in the nature of random hits, a researcher was able to trace a number of people of Chinese descent... and confirm their linkage to Genghis Khan ; all through genetics.

The story of our genes is the story of violence, of passion, of conquest and assimilation, as told in this article in Popular Science.

Article Extract: Scientists have previously used genes to trace immigrations in the Caribbean and the Indian subcontinent. Now, an ambitious new project has attempted to use genetics to identify many of the major movements of humans over the last 4,000 years. The New York Times has a nice graphic showing how genes are able to trace populations. When two populations meet, they tend to mix genes. If two populations met recently, the pieces of DNA they inherit from one another tend to be large. If they met generations ago, then the pieces of DNA they inherit from each other are smaller.

By measuring the sizes of different chunks of DNA in modern people, a team of geneticists and statisticians from the U.K. and Germany identified more than 100 major population movements. They saw the spread of Mongol genes across the Mongol empire, the appearance of European genes in Maya and Pima Indians during colonization, and the arrival of Cambodian genes at the fall of the Khmer empire. The scientists also made an interactive map where you can explore the ancestry of people around the world. The scientists never needed to consult historians to find evidence of these historical events, which is pretty cool.

Article Link: http://www.popsci.com/article/science/modern-genes-reveal-100-major-population-shifts-human-history?dom=PSC&loc=recent&lnk=8&con=modern-genes-reveal-100-major-population-shifts-in-human-history

Sciencemag (Genetic Atlas) : http://www.sciencemag.org/content/343/6172/747.abstract?rss=1

The interactive map (Read the instructions) : http://www.admixturemap.paintmychromosomes.com/

Pic courtesy : Spread of Mongol Empire. Astrokey44 on Wikimedia Commons, CC BY-SA 3.0 (from PopSci).

#genes #history #tracingyourroots #science  
Animated Photo
Add a comment...

Post has attachment
Cat domestication : A new study points to the domestication of Cats beginning in China. I earlier posted about a study which assumed that the earliest domestication of cats to be in Egypt around 4,000 years ago (http://goo.gl/CKK3a0), though the study in PNAS looks at domestication 5300 years ago..... read on...

Article Extract: The earliest evidence for cat domestication comes from Chinese farms dating to 5300 years ago, a new study confirms. It looks like China beat Egypt as being the first to discover the merits of cats. The findings, published in the Proceedings of the National Academy of Sciences, pinpoint the early Chinese village of Quanhucun as being the likely ground zero for cat domestication.

"Our data suggest that cats were attracted to ancient farming villages by small animals, such as rodents that were living on the grain that the farmers grew, ate and stored." She continues, "Results of this study show that the village of Quanhucun was a source of food for the cats 5300 years ago, and the relationship between humans and cats was commensal, or advantageous for the cats. Even if these cats were not yet domesticated, our evidence confirms that they lived in close proximity to farmers, and that the relationship had mutual benefits."

The researchers found that the cats were eating grain millet grown by the farmers. Yet another ate so much human-grown grain that the researchers suspect it was fed. The researchers also determined that farmers then were battling rodents, since they found an ancient rodent burrow into a grain storage pit and grain storage pots designed to be rodent proof. It probably didn't take long for the farmers to figure out that the cats went after the rats and mice, so they were good animals to keep around.

Article Link: http://www.abc.net.au/science/articles/2013/12/17/3913002.htm

Research Paper: http://www.pnas.org/content/early/2013/12/12/1311439110

Additional link: http://news.discovery.com/animals/pets/cat-domestication-traced-to-early-chinese-farms-131216.htm

Pic source: http://www.inkdancechinesepaintings.com/cat/painting-4379005.html and abc.net.au

#caturday #china #science #domestication  
Photo
Photo
2014-01-04
2 Photos - View album
Add a comment...

Post has attachment
The Pleistocene hanky-panky chart : Apparently there was interbreeding between Humans with Denisovans and Neanderthals. Read on to know more...

Article Extract: Now that scientists have sequenced a complete Neanderthal genome, we have more evidence than ever that early Homo sapiens had children with Neanderthals and Denisovans tens of thousands of years ago.

This chart, from Nature, is part of a paper published this week by evolutionary biologist Svante Pääbo's team at the Max Planck Institute in Germany, where they sequenced an entire Neanderthal genome from a well-preserved toe bone. It shows three known early human groups — Homo sapiens, Neanderthal, and Denisovan — as well as an unknown one that might be Homo erectus. We see when these groups diverged, and when they (ahem) came together again.

The comparison shows that Neanderthals and Denisovans are very closely related, and that their common ancestor split off from the ancestors of modern humans about 400,000 years ago. Neanderthals and Denisovans split about 300,000 years ago. Though Denisovans and Neanderthals eventually died out, they left behind bits of their genetic heritage because they occasionally interbred with modern humans. The research team estimates that between 1.5 and 2.1 percent of the genomes of modern non-Africans can be traced to Neanthertals.

Article Link: http://io9.com/a-chart-that-sums-up-who-had-sex-with-whom-during-the-p-1486738108

Additional link: http://newscenter.berkeley.edu/2013/12/18/neanderthal-genome-shows-evidence-of-early-human-interbreeding-inbreeding/

NYT Article (related) :http://www.nytimes.com/2013/12/19/science/toe-fossil-provides-complete-neanderthal-genome.html?pagewanted=2&_r=0

Nature paper: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12886.html

#human #DNA #science  
Photo
Add a comment...

Post has attachment
Ancient Neanderthal and Denisovan retroviruses found in Humans : An unrelated (cancer) study shows that retroviruses inserted themselves in Homo Sapiens after the split from the Neanderthal and Denisovan species. While not found in all humans, it goes to show that some of us have more in common with our ancient Neanderthal and Denisovan cousins... interesting indeed.

Article Extract: Neanderthals and Denisovans may be long gone, but their viruses continue to live on inside our bodies. The geneticists who discovered these ancient viruses aren't sure if they're bad for us, but they could make us more susceptible to certain cancers. The conclusion was, was that these Neanderthal and/or Denisovan ERVs must have inserted themselves into their respective genomes after the ancient relatives/human split. But speciation isnt a ‘clean’ break. It's not as if one day there is a human/Neanderthal/Denisovan ancestor, and the next day there are humans and Neanderthals and Denisovans. Speciation is a time consuming, tangled up mess.

Modern humans (Homo sapiens) last shared a common ancestor with two types of archaic hominins, Neandertals and Denisovans, roughly 800,000 years ago, and the population leading to modern H. sapiens separated from that leading to Neandertals and Denisovans roughly 400,000 years ago. Neanderthals co-existed with our ancestors in Europe for thousands of years, but belonged to a different human sub-species. They eventually became extinct around 30,000 years ago.
 
Article Link: http://scienceblogs.com/erv/2013/11/21/neanderthal-and-denisovan-retroviruses-in-you/

Earlier post: Human migration mapping using genetics: http://goo.gl/iy9IjA

Earlier post: Neanderthal cousins may be assimilated in us: http://goo.gl/PfxI2s

Earlier post on interbreeding: http://goo.gl/zYKDZQ

Earlier post on Humans travelled from Asia to America : http://goo.gl/voYyu4

iO9 Link: http://io9.com/modern-humans-are-still-carrying-neanderthal-viruses-1467642087

Research paper: http://www.cell.com/current-biology/abstract/S0960-9822%2813%2901269-4

Scienceblogs link: http://scienceblogs.com/erv/2013/11/21/neanderthal-and-denisovan-retroviruses-in-you/

What is a retrovirus: http://en.wikipedia.org/wiki/Retrovirus

http://www.dailymail.co.uk/sciencetech/article-2509455/Neanderthal-viruses-dating-500-000-years-discovered-modern-human-DNA.html

Pics courtesy: Natgeo http://goo.gl/PrQFIM, Smithsonian http://goo.gl/m7Dc9r (Neanderthal Skull: bottom right, Homo Erectus: top right).
PhotoPhotoPhoto
2013-12-02
3 Photos - View album
Add a comment...

Post has attachment
Ginger hair : Mapping the human genome is fascinating... so many new theories are coming to light. Here is one about Ginger hair.

Article extract: Scientists believe that the “ginger gene,” or “V6OL allele,” showed up 50,000 years ago after humans left Africa for colder climates. This gene made human’s skin lighter, as they were exposed to less vitamin D from the sun. Ten percent of Irish people have red hair. In total there are 20 million people in the United Kingdom and Ireland with the gene that can cause red hair and this new study shows that this remains a dominant gene in southern Europeans today.
 
However, this paler skin also brought health risks, such as melanoma, the deadliest form of cancer, but the study’s author Doctor Saioa Lopez says this is not necessarily due to the redhead gene itself. The recent study follows on the results of a ScotlandsDNA project in 2012 which found that the Celts flaming red hair can be put down to the weather. The experts believe that the gloomy climate in Scotland has seen a deliberate genetic adaptation. Essentially this means that red hair helps to take advantage of sunny days and allows the body to absorb more vitamin D.

Main article: http://www.irishcentral.com/news/Could-Irelands-cloudy-weather-be-the-reason-for-the-stereotypical-red-hair-178077221.html

Link to ScotlandsDNA project: http://www.ibtimes.com/why-does-scotland-have-so-many-redheads-863366

Related research link: http://goo.gl/uCPRnv

Pics courtesy: Irishcentral, colorfulcandys.

#irish #ginger #evolution #genetics #science #scienceeveryday  
Photo
Photo
2013-09-26
2 Photos - View album
Add a comment...

Post has attachment
Human Migration mapping using Genetics : Our species, Homo sapiens, evolved in Africa about 200,000 years ago. Genomics shows that early Asian and European populations originated from small African groups who started moving to the Middle East about 60,000 years ago. Those small groups carried only a small fraction of Africa’s genomic diversity. Even today, the genomes of modern African populations are far more diverse than those of Asians and Europeans.

Our DNA also reveals that our species mixed with ancient human species that are now extinct – Neanderthals in Europe, and a mysterious Asian group called Denisovans. Small amounts of Neanderthal or Denisovan DNA sequences are found in the genomes of some 21st century people.

Through migration and mixing populations, all the while encountering new environments and diets, DNA variants spread across many populations. Nevertheless, the genomes of any two unrelated people today are about 99.9 percent alike, and small differences in our appearance, or our risk or protection from disease, are reminders of how our ancestors were shaped by different environments on their journeys across the world.

Article Link: http://unlockinglifescode.org/explore/our-genomic-journey

NYT Link: http://www.nytimes.com/2013/08/30/arts/design/genome-unlocking-lifes-code-at-the-smithsonian.html?ref=science

Further reading: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3738866/

Earlier post on Human migration: https://plus.google.com/103586346709495625226/posts/4dRQKdV7nfH

Earlier post on Neanderthals : https://plus.google.com/110884604033336753419/posts/bJ1pksfFoNu

Earlier post on migration map: https://plus.google.com/110884604033336753419/posts/UXXLSYK6PjD

Peopling of the world: https://plus.google.com/110884604033336753419/posts/2VbewDcs1sS

#science #scienceeveryday #humanmigration #human #mapping #genome #genomeproject  
Photo
Photo
2013-09-01
2 Photos - View album
Add a comment...

Post has attachment
Neanderthal cousins may be Assimilated in us

Neanderthals were humans who went extinct between 20,000 and 30,000 years ago. Though there is some debate about who these people were, there is no question that there are none left. Around 40,000 years ago, humans had spread in waves across most of the world, from Africa to Europe, Asia, and even Australia. But these humans were not all perfectly alike. When some groups of H. sapiens poured out of Africa, they walked north, then west. In this thickly forested land, they came face-to-face with other humans, stockier and lighter skinned than themselves, who had been living for thousands of years in the cold wilds of Europe, Russia, and Central Asia. Today we call these humans Neanderthals.

A few decades ago, most scientists would have answered that it was a nightmare, a extinction of a people, a holocaust. Today, however, there is a growing body of evidence from the field of population genetics that tells a very different story about what happened when the two groups of early humans lived together, sharing the same caves and hearths. Anthropologists like Milford Wolpoff, of the University of Michigan, and John Hawks have suggested that the two groups formed a new, hybrid human culture. Instead of exterminating Neanderthals, their theory goes, H. sapiens had children with them until Neanderthals’ genetic uniqueness slowly dissolved into H. sapiens over the generations. This idea is supported by compelling evidence that modern humans carry Neanderthal genes in our DNA.

We have only fragmentary evidence of what Neanderthal life was like before the arrival of H. sapiens. Though they would have looked different from H. sapiens, they were not another species. Some anthropologists call Neanderthals a “subspecies” to indicate their evolutionary divergence from us, but there is strong evidence that Neanderthals could and did interbreed with H. sapiens.

Main Article Link: http://www.popsci.com/science/article/2013-05/how-avoid-meeting-neanderthals-fate

The Human Genome Project: https://plus.google.com/u/0/103586346709495625226/posts/4dRQKdV7nfH

Neanderthals and Humans: https://plus.google.com/u/0/110884604033336753419/posts/GHaTFfCyneK

MtDNA Migration map: https://plus.google.com/u/0/110884604033336753419/posts/UXXLSYK6PjD
The Journey of Mankind: https://plus.google.com/u/0/110884604033336753419/posts/2VbewDcs1sS

When Humans came out of the Americas: https://plus.google.com/u/0/110884604033336753419/posts/JPgZBcxVyGb

#science #scienceeveryday #genome #neanderthal #map #journey #man #history  
Photo
Photo
2013-05-19
2 Photos - View album
Add a comment...
Wait while more posts are being loaded