Weekend Feature: Phantom Black Holes of the Milky Way --Could They Pose a Danger to Our Solar System?
From the 'X-File' Dept: Michio Kaku --"Civilizations of the Cosmos"

Weekend Feature: Human Genome Reveals Entire Span of Species--From Near Extinction to Space Age




Stored inside your genome are clues to the history of humankind, including global migrations and population crashes, according to researchers who have analyzed DNA pioneer, Craig Venter's publicly published DNA sequence, and those of 6 others, to reveal major milestones in human history.

The analysis suggests that descendants of the first humans to leave Africa shrunk to as few as 1,000 reproductively active individuals before rebounding. The study also suggests that, contrary to popular theories, these early humans continued to breed with sub-Saharan Africans until as recently as 20,000 years ago.

Genetic researchers have traditionally compared DNA sequences from populations around the world to determine how populations relate to one another and when they might have branched off. Studies of DNA from maternally inherited cell structures called mitochondria, for example, established that all humans can trace their maternal lineage back to one mitochondrial Eve who lived in Africa around 200,000 years ago.

"Each little piece of the genome has its own unique bit of history and goes to a unique ancestor as you go further and further back," explained John Novembre, a population geneticist at UCLA. "As you look at different parts of the genome, you get access to different parts of history."

On the basis of this principle, Richard Durbin, a genome scientist at the Wellcome Trust Sanger Institute near Cambridge, UK, and Heng Li determined a way to calculate, from the ages of different segments of a single person's genome, changes in the population size of their ancestors.

The genomes of Venter and two others of European ancestry, two Asian men and two West African men all tell the same story up until about 100,000 years ago, when their populations began to split and then plummet in size, reflecting, it is believed, the first human migrations out of Africa.

The ancestors of Asians and Europeans dwindled by a factor of ten to roughly 1,200 reproductively active people between 20,000 and 40,000 years ago, Durbin and Li calculated. African populations also crashed, but by nowhere near the same extent, dropping to around 5,700 breeding individuals. Other studies have recorded population crashes at around the same time, Reich says.

In a seperate analysis, Durbin and Li compared an X chromosome from an African with one from a non-African to determine when their ancestors stopped interbreeding after the first humans left Africa and colonized other parts of the world. Human remains and artefacts unearthed in Europe, Asia and Australia seem to suggest humans rapidly colonized these places by about 40,000 years ago, diminishing the opportunities to interbreed with Africans.

Durbin and Li suggest that these groups continued to interbreed until as recently as 20,000 years ago. One possible explanation, Durbin says, is that after the first humans left Africa some 60,000 years ago, successive waves of Africans followed suit, interbreeding with the ancestors of the earlier migrants.

Mining individual genomes can't reveal every chapter of human history, notes David Reich, who works with Li at the Broad Institute of Harvard and MIT in Cambridge, Massachusetts. The approach reveals little about upheavals of the last 20,000 years, such as the peopling of the Americas, because few chunks of the genome are young enough. Similarly, Durbin and Li's method can't deduce the history of human ancestors who existed before about 2 million years ago because few regions of the genome are much older.

Reich, a geneticist and professor in the department of genetics at the Harvard Medical School. told nature.com that he plans to lean heavily on the new approach, not least for work on ancient genomes belonging to Neanderthal  and a mysterious sister population, known as Denisovans, discovered through DNA recovered from a 30,000–50,000-year-old finger bone found in a Siberian cave. 

The Daily Galaxy via nature.com/news



This is fascinating. Exciting even. Too bad so many people won't even believe it.

Please put link and information such as the paper title etc so we can look up the detailed information. The link about is dead. There is no point in writing interesting articles that have
little or no follow up detail.


Editor's Note: Corrected. Thanks.

The Daily Galaxy is censoring the comments by removing texts they don't understand or don't like.
What are they? The new Joseph Goebbels ancestors? The nazi times are over.
Where the freedom of free scientific position? Editors Note: We delete annoying spam as a courtesy to others.

Try this link.

This population minimum of 1200 individuals capable of reproduction around 20-40000 years ago comes pretty much at the time of the demise of the Neanderthals. Curious or no?

is the title indicating anything about advanced beings interbreeding(ex. aliens) with humans or is that just a flashy way to grab attention?

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