They're getting closer and closer and closer...to the truth. I made a few notes, denoted in brackets within the text.
From The New York Times, July 4, 2017, by Carl Zimmer:
In Neanderthal DNA, Signs of a Mysterious Human Migration
With fossils and DNA, scientists are piecing together a picture of humanity’s beginnings, an origin story with more twists than anything you would find at the movie theater.
The expert consensus now is that Homo sapiens evolved at least 300,000 years ago in Africa. Only much later — roughly 70,000 years ago — did a small group of Africans establish themselves on other continents, giving rise to other populations of people today.
To Johannes Krause, the director of the Max Planck Institute for Human History in Germany, that gap seems peculiar. “Why did people not leave Africa before?” he asked in an interview. After all, he observed, the continent is physically linked to the Near East. “You could have just walked out."
In a study published Tuesday in Nature Communications, Dr. Krause and his colleagues report that Africans did indeed walk out — over 270,000 years ago.
Based on newly discovered DNA in fossils, the researchers conclude that a wave of early Homo sapiens, or close relatives of our species, made their way from Africa to Europe. There, they interbred with Neanderthals.
Then the ancient African migrants disappeared. But some of their DNA endured in later generations of Neanderthals.
"This is now a comprehensive picture,” Dr. Krause said. “It brings everything together."
Showing posts with label DNA and evolution. Show all posts
Showing posts with label DNA and evolution. Show all posts
Sunday, July 9, 2017
Sunday, March 30, 2014
So-Called "Neanderthal" and So-Called "Modern Human" DNA - This Story Ain't Going Away
This just makes me laugh, LOL! So-called "evolution" is getting more complicated by the second? Gee, I wonder why? Maybe because the entire "theory" needs to be junked...
Article from Nature.com
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| Photo Adapted from: Tetra Images/Alamy (from article) |
Article from Nature.com
Human evolution: The Neanderthal in the family
Thirty years after the study of ancient DNA began, it promises to upend our view of the past.
An equine oddity with the head of a zebra and the rump of a donkey, the last quagga (Equus quagga quagga) died in 1883. [What a dirty rotten shame that we let that happen then, and we're still letting it happen today. When a species goes extinct, do we not also lose a piece of our own herstory?] A century later, researchers published1 around 200 nucleotides sequenced from a 140-year-old piece of quagga muscle. Those scraps of DNA — the first genetic secrets pulled from a long-dead organism — revealed that the quagga was distinct from the mountain zebra (Equus zebra).
More significantly, the research showed that from then on, examining fossils would no longer be the only way to probe extinct life. “If the long-term survival of DNA proves to be a general phenomenon,” geneticists Russell Higuchi and Allan Wilson of the University of California, Berkeley, and their colleagues noted in their quagga paper1, “several fields including palaeontology, evolutionary biology, archaeology and forensic science may benefit.”
At first, progress was fitful. Concerns over the authenticity of ancient-DNA research fuelled schisms in the field and deep scepticism outside it. But this has faded, thanks to laboratory rigour that borders on paranoia and sequencing techniques that help researchers to identify and exclude contaminating modern DNA.
These advances have fostered an ancient-genomics boom. In the past year, researchers have unveiled the two oldest genomes on record: those of a horse that had been buried in Canadian permafrost for around 700,000 years2, and of a roughly 400,000-year-old human relative from a Spanish cavern3. A Neanderthal sequence every bit as complete and accurate as a contemporary human genome has been released4, as has the genome of a Siberian child connecting Native Americans to Europeans5.
Enabling this rush are technological improvements in isolating, sequencing and interpreting the time-ravaged DNA strands in ancient remains such as bones, teeth and hair. Pioneers are obtaining DNA from ever older and more degraded remains, and gleaning insight about long-dead humans and other creatures. And now ancient DNA is set to move from the clean-rooms of specialists to the labs of archaeologists, population geneticists and others. Thirty years after the quagga led the way, Nature looks to the field's future.
Friday, January 11, 2013
DNA Showing We're Not a Tree - We're a Bramble Bush!
A History Lesson from Genes: Using DNA to Tell Us How Populations Change
Jan. 9, 2013 — When Charles Darwin first sketched how species evolved by natural selection, he drew what looked like a tree. The diagram started at a central point with a common ancestor, then the lines spread apart as organisms evolved and separated into distinct species.
In the 175 years since, scientists have come to agree that Darwin's original drawing is a bit simplistic, given that multiple species mix and interbreed in ways he didn't consider possible (though you can't fault the guy for not getting the most important scientific theory of all time exactly right the first time). Using a tree-like structure is a great way to show the history of the evolution of a species, or its phylogeny. But it's not so great for showing the population history of groups within a single species, such as humans, who can move around and interbreed with each other.
Jonathan Pritchard, PhD, professor in the department of human genetics, studies the nature of these human genetic variations by combining methods from evolutionary biology and statistics. Intrigued by recent research on the Neanderthal genome that suggests more interbreeding with Homo sapiens than previously thought, Pritchard wanted to develop a general method for estimating gene flow between different groups within the same species over time. In a recent paper published in PLOS Genetics, he and Joseph Pickrell, a former University of Chicago researcher now at Harvard, described a software model they developed that can infer the history of population splits and mixtures within a species based on modern DNA.
"If you try to make a tree of population histories within a species, there's always the possibility that you've got genes flowing from one branch to another," Pritchard said. "The populations can interbreed, so if they're geographically together or if there's movement from one place to another, then this tree representation is not necessarily going to be a good way of representing history. The goal of this research is to learn more about departures from 'tree-ness.'"
Pritchard and Pickrell developed software called TreeMix that compares how often variants of a particular gene from different populations appear in the same species. It then calculates how closely groups are related, and when in their history they separated to form a genetically distinct population or breed.
The resulting graph looks less like tree branches and more like a tangled shrub or mass of vines. The trunk of the shrub represents the major relationships between the groups, and the largest branches represent distinct populations as they develop over time from left to right on the graph. But those tangled vines that crisscross the branches are the key, showing migration events where a previously separate population mixed with another, rejoining to form a new group at a later point in time.
Pritchard and Pickrell tested the model using DNA from 55 human populations and 82 dog breeds, and already found some interesting results. For example, boxer and basenji breeds of dogs trace a large portion of their DNA (nine percent and 25 percent, respectively) back to wolves after domestication, meaning that these breeds interbred with wolves again after humans had begun to domesticate dogs.
"What I like about this is that it's starting to give us some resolution on relationships that are just much more complicated than you can capture using the standard tree approach," Pritchard said.
He gave another example of the Mozabite people who live in Algeria. Their DNA is largely a mixture of European and Middle Eastern ancestry, but they also mixed with sub-Saharan African ancestors at various points in their history. The new model can represent the complex relationships among all of these backgrounds, whereas the traditional tree-based method would just show a primary relationship to Middle Easterners.
Another group of researchers has already used Pritchard's software to show a link between Denisovans, an extinct relative of Neanderthals found in Siberia, and Papuans in the South Pacific. It doesn't make geographic sense right away, but such a finding forces researchers to ask more questions about how these groups migrated and changed over time. Much like DNA evidence has revolutionized criminal investigations, often negating assumptions based on physical evidence, advanced genetic analysis like Pritchard's can change what we think about human history as well.
I recommend taking a look at the illustration that is included in the article, above -- I did not reproduce it here. I need to have it explained to me because I don't know if I'm "reading" it correctly. If I am, it sure is showing some absolutely remarkable and fascinating things about how our human ancestors met, mated, and parted, and met, mated and parted with others, either much, or not so much!
Jan. 9, 2013 — When Charles Darwin first sketched how species evolved by natural selection, he drew what looked like a tree. The diagram started at a central point with a common ancestor, then the lines spread apart as organisms evolved and separated into distinct species.
In the 175 years since, scientists have come to agree that Darwin's original drawing is a bit simplistic, given that multiple species mix and interbreed in ways he didn't consider possible (though you can't fault the guy for not getting the most important scientific theory of all time exactly right the first time). Using a tree-like structure is a great way to show the history of the evolution of a species, or its phylogeny. But it's not so great for showing the population history of groups within a single species, such as humans, who can move around and interbreed with each other.
Jonathan Pritchard, PhD, professor in the department of human genetics, studies the nature of these human genetic variations by combining methods from evolutionary biology and statistics. Intrigued by recent research on the Neanderthal genome that suggests more interbreeding with Homo sapiens than previously thought, Pritchard wanted to develop a general method for estimating gene flow between different groups within the same species over time. In a recent paper published in PLOS Genetics, he and Joseph Pickrell, a former University of Chicago researcher now at Harvard, described a software model they developed that can infer the history of population splits and mixtures within a species based on modern DNA.
"If you try to make a tree of population histories within a species, there's always the possibility that you've got genes flowing from one branch to another," Pritchard said. "The populations can interbreed, so if they're geographically together or if there's movement from one place to another, then this tree representation is not necessarily going to be a good way of representing history. The goal of this research is to learn more about departures from 'tree-ness.'"
Pritchard and Pickrell developed software called TreeMix that compares how often variants of a particular gene from different populations appear in the same species. It then calculates how closely groups are related, and when in their history they separated to form a genetically distinct population or breed.
The resulting graph looks less like tree branches and more like a tangled shrub or mass of vines. The trunk of the shrub represents the major relationships between the groups, and the largest branches represent distinct populations as they develop over time from left to right on the graph. But those tangled vines that crisscross the branches are the key, showing migration events where a previously separate population mixed with another, rejoining to form a new group at a later point in time.
Pritchard and Pickrell tested the model using DNA from 55 human populations and 82 dog breeds, and already found some interesting results. For example, boxer and basenji breeds of dogs trace a large portion of their DNA (nine percent and 25 percent, respectively) back to wolves after domestication, meaning that these breeds interbred with wolves again after humans had begun to domesticate dogs.
"What I like about this is that it's starting to give us some resolution on relationships that are just much more complicated than you can capture using the standard tree approach," Pritchard said.
He gave another example of the Mozabite people who live in Algeria. Their DNA is largely a mixture of European and Middle Eastern ancestry, but they also mixed with sub-Saharan African ancestors at various points in their history. The new model can represent the complex relationships among all of these backgrounds, whereas the traditional tree-based method would just show a primary relationship to Middle Easterners.
Another group of researchers has already used Pritchard's software to show a link between Denisovans, an extinct relative of Neanderthals found in Siberia, and Papuans in the South Pacific. It doesn't make geographic sense right away, but such a finding forces researchers to ask more questions about how these groups migrated and changed over time. Much like DNA evidence has revolutionized criminal investigations, often negating assumptions based on physical evidence, advanced genetic analysis like Pritchard's can change what we think about human history as well.
****************************************************
I recommend taking a look at the illustration that is included in the article, above -- I did not reproduce it here. I need to have it explained to me because I don't know if I'm "reading" it correctly. If I am, it sure is showing some absolutely remarkable and fascinating things about how our human ancestors met, mated, and parted, and met, mated and parted with others, either much, or not so much!
Sunday, September 23, 2012
DNA Study Raises More Questins Than It Answers
Link to article:
Extensive DNA Study Sheds Light on Modern Human Origins
September 20, 2012
"The deepest divergence of all living people occurred some 100,000 years ago, well before modern humans migrated out of Africa and about twice as old as the divergences of central African Pygmies and East African hunter-gatherers and from other African groups," says lead author Dr Carina Schlebusch, a Wits University PhD-graduate now conducting post-doctoral research at Uppsala University in Sweden.
Questions: Does this mean that African Pygmies and the "East African hunter-gatherers and 'other African groups' are not human as we understand the term today? If they are not human, what are they?
Question: Does this mean that once this "divergence" of the Khoe and San tribes took place in Africa, no further "evolution" happened? Are we not all still homo sapiens sapiens, despite thousands of years passing since this "divergence" -- well, except for problem groups like the Pygmies (and let us not forget so-called 'Neanderthal' man, and the mysterious Denisovians)? Are not Pygmies still Pygmies after even more thousands of years of their assumed "divergence" from whomever they are supposed to have "diverged" from?
Question: What is the difference between genetic drift and "evolution?"
The researchers also looked for signals across the genome of ancient adaptations that happened before the historical separation of the Khoe-San lineage from other humans. "Although all humans today carry similar variants in these genes, the early divergence between Khoe-San and other human groups allowed us to zoom-in on genes that have been fast-evolving in the ancestors of all of us living on the planet today," said Pontus Skoglund from Uppsala University.
Among the strongest candidates were genes involved in skeletal development that may have been crucial in determining the characteristics of anatomically modern humans.
Question: If in the past certain genes were capable of "fast-evolving" - is this still happening today? If not, why not? And, if so, where is the evidence of human beings "evolving" into something - other?
Extensive DNA Study Sheds Light on Modern Human Origins
September 20, 2012
"The deepest divergence of all living people occurred some 100,000 years ago, well before modern humans migrated out of Africa and about twice as old as the divergences of central African Pygmies and East African hunter-gatherers and from other African groups," says lead author Dr Carina Schlebusch, a Wits University PhD-graduate now conducting post-doctoral research at Uppsala University in Sweden.
Questions: Does this mean that African Pygmies and the "East African hunter-gatherers and 'other African groups' are not human as we understand the term today? If they are not human, what are they?
Question: Does this mean that once this "divergence" of the Khoe and San tribes took place in Africa, no further "evolution" happened? Are we not all still homo sapiens sapiens, despite thousands of years passing since this "divergence" -- well, except for problem groups like the Pygmies (and let us not forget so-called 'Neanderthal' man, and the mysterious Denisovians)? Are not Pygmies still Pygmies after even more thousands of years of their assumed "divergence" from whomever they are supposed to have "diverged" from?
Question: What is the difference between genetic drift and "evolution?"
The researchers also looked for signals across the genome of ancient adaptations that happened before the historical separation of the Khoe-San lineage from other humans. "Although all humans today carry similar variants in these genes, the early divergence between Khoe-San and other human groups allowed us to zoom-in on genes that have been fast-evolving in the ancestors of all of us living on the planet today," said Pontus Skoglund from Uppsala University.
Among the strongest candidates were genes involved in skeletal development that may have been crucial in determining the characteristics of anatomically modern humans.
Question: If in the past certain genes were capable of "fast-evolving" - is this still happening today? If not, why not? And, if so, where is the evidence of human beings "evolving" into something - other?
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