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Decoded:
The Mystery of Human Migration Eggshells
reveal birds’ evolutionary secrets Prof Yash
Pal This
Universe Trends |
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Decoded: The Mystery of Human Migration IT is the greatest journey in history, and now the story of how the first members of our species walked out of their African homeland to colonise almost every corner of the world is being told by reading the DNA of their living descendents. Half a million people from around the globe are participating in an ambitious project to reconstruct some of the ancient migratory routes that took Homo sapiens from their ancient African homelands to the relatively new territories of Asia, Europe, Oceania and America. Hidden within the genetic makeup of people alive today is the encoded story of how their ancient ancestors made this epic journey, which covered many thousands of miles over many tens of thousands of years to complete. The Genographic Project, a landmark study into ancient human migrations, aims to decode these hidden signposts within our DNA. By doing so, the project hopes to unravel the complex movements of the earliest men and women who were driven through necessity or curiosity to explore new territories and establish fresh roots in strange lands. Human palaeontology, the study of ancient remains, suggests that the species Homo sapiens originated in Africa, probably East Africa, about 200,000 years ago, but it was only about 60,000 years ago that anatomically modern humans began their long and arduous journey out of Africa. In recent years, with the ability to decode the human genome quickly and cheaply, it has been possible to compare the palaentological record with historical information on human movements stored within our DNA. Over time, human DNA has amassed a bewildering variety of mutations that scientists can now exploit to build a picture of how men and women today are descended from the first people who moved along these ancient migratory routes. One of the first big surprises of the Genographic Project, for instance, is the discovery that the initial journey out of Africa may not have been through the “northern route” of the Sinai Peninsula and Middle East, as initially proposed. Instead, they seem to have moved out of Africa by a “southern route” at the Bab-el-Mandeb straits at the mouth of the Red Sea separating East Africa from southern Arabia. This migration may have required boats to traverse the shallow waters that would have existed there 60,000 years ago. But even with this apparent physical obstacle, scientists believe that the DNA analysis of the female X chromosome of present-day humans suggests it is still the most likely route taken out of Africa. “This was really the first study that had used that kind of genetic information to look at global patterns of human variability,” said Spencer Wells, director of the Genographic Project and explorer-in-residence at National Geographic, one of the project’s sponsors. “What it confirmed was that the earliest migration out of Africa, and probably the major migration, had gone out through the Bab-el-Mandeb Strait to India. There could have been subsequent migrations out via the Middle East but certainly the majority of people trace back to that original migration event, and we’re still tracing out the details of exactly what happened.” The DNA evidence shows clearly and unequivocally that Africa was the homeland of anatomically modern humans, neat, independent confirmation of the palaeontology. The genetic variation within people living in Africa, which is related to the length of time spent on the continent, is greater than all the variation in the rest of the world put together. “We see more variation in Africa than in any other group, so that tells us we’ve been accumulating variation for longer than in any other group,” Dr Wells added. “Outside of Africa, we see more variation in India than anywhere else which tells use we’ve been living in India for longer than any other place outside Africa. The question is, how many waves of migration out of Africa were there, and what were the timings of those events?” The information being gathered by the Genographic Project is starting to put dates to the key crossroads in the greatest journey of human history.
— The Independent
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Eggshells reveal birds’ evolutionary secrets SYDNEY: Molecules from eggshells of endangered and extinct birds can tell behaviour and evolutionary history of Australian feathered fauna, reveals a study. James Haile from Murdoch University, who pioneered the breakthrough technique, says eggshell has been largely overlooked as a source of information, despite its impermeability and resistance to decay, owing largely to the calcium carbonate matrix which acts to protect biomolecules. Haile says researchers take the eggs of extinct and endangered birds and grind them down before sequencing the DNA to learn new information about these birds, the journal ScienceNetwork WA reported. “For extinct birds, such as Madagascar’s elephant bird, we extract the DNA and compare that to living birds such as emu, cassowary, ostrich and others — from that we can see how those birds fit into the broader family tree and at what point they diverged,” said Haile, according to a university statement. “For the endangered birds, we take samples of abandoned eggshells and together with DNA samples from chicks and captive birds develop a population database to get a picture of genetic diversity of the population,” he said. The application of my research can help to identify smuggled eggs coming into Australia and learn more about the behavior of Australia’s endangered birds for conservation strategies, said Haile. It could even help determine the precise timing of the fragmentation of the supercontinent Gondwana, he said. “Elephant bird eggs are the largest ever known, bigger than any dinosaur egg, and very resistant to decay. So they’re an ideal but under research source of DNA,” he added.
— IANS
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This Universe If the sun is supposed to be emitting white light, then why does it appear yellow-orange, and the sky blue? We have to realise that sitting on the earth surface, we see sunlight as it reaches us after traversing about a thousand grams per centimeter square of atmosphere. We do have the lucky circumstance that our atmosphere is fairly transparent to light, but we are also fortunate that it is not completely transparent. It does absorb and scatter the radiation passing through it. One significant feature is that this obstruction and alteration by the atmosphere, though not very significant or harmful, produces for us a unique environment. If the atmosphere were completely transparent, then we would have seen stars during the day also. Our sky would have been pitch dark dotted with shining stars and we would not have had any notion of the blue skies we delight in. Also, the colour of the sun would have been the same during the day and not varied as it does, becoming orange red at dusk and dawn because of increased path length through the atmosphere. This change in colour and the blue colour of the sky itself are due to strong wavelength dependence of light scattering-blue light scatters almost eight times more than the red. We as humans are enormously lucky to have had the kind of world we have, and the laws that control our environment and living. Readers wanting to ask Prof Yash Pal a question can e-mail him at palyash.pal@gmail.com
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Trends NEW YORK: With mounting evidence linking hundreds of small earthquakes from Oklahoma to Ohio to the energy industry's growing use of fracking technology, scientists say there is one way to minimise risks of even minor temblors. Only, it costs about $10 million a pop. WHO ‘deeply concerned’ about mutated birdflu research LONDON: The World Health Organisation has issued a stern warning to scientists who have engineered a highly pathogenic form of the deadly H5N1 bird flu virus, saying their work carries significant risks and must be tightly controlled. The United Nations health body said it was "deeply concerned about the potential negative consequences" of work by two leading flu research teams who this month said they had found ways to make H5N1 into a easily transmissible form capable of causing lethal human pandemics.
— Reuters |
A
new study aims to analyse modern DNA to track how mankind spread across the
globe
