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How the human penis lost its spines
By Elizabeth Landau, CNN
March 9, 2011 6:00 p.m. EST
Scientists are seeking to understand the underlying reasons why humans and chimpanzees have key differences.
(CNN) -- You've read the headline, and it probably made you giggle. Go ahead. Get it out of your system. Then take a deep breath and consider how evolution affected a few specific body parts, and why.
Humans and chimpanzees share more than 97% of DNA, but there are some fairly obvious differences in appearance, behavior and intellect. Now, scientists are learning more than ever about what makes us uniquely human.
We know that humans have larger brains and, within the brain, a larger angular gyrus, a region associated with abstract concepts. Also, male chimpanzees have smaller penises than humans, and their penises have spines. Not like porcupine needles or anything, but small pointy projections on the surface that basically make the organ bumpy.
Gill Bejerano, a biologist at Stanford University School of Medicine, and colleagues wanted to further investigate why humans and chimpanzees have such differences. They analyzed the genomes of humans and closely related primates and discovered more than 500 regulatory regions -- sequences in the genome responsible for controlling genes -- that chimpanzees and other mammals have, but humans do not. In other words, they are making a list of DNA that has been lost from the human genome during millions of years of evolution. Results from their study are published in the journal Nature.
Think of it like light bulbs and their switches, where the light bulbs are genes and the switches are these controlling DNA sequences. If there's no bulb, the switch can't turn the light on. Now imagine there's one bulb and five switches to turn it on at different times in different places. If you take one of the switches away, the bulb still works in the four other contexts, but not in the fifth.
This study looks at two particular switches. Bejerano and colleagues took the switch information from a chimpanzee's genome and essentially "hooked it up" to a reporter gene, a gene whose effects scientists can track as an organism develops. They injected the reporter gene in a mouse egg to see what the switch would do.
They found that in one case, a switch that had been lost in humans normally turns on an androgen receptor at the sites where sensory whiskers develop on the face and spines develop on the penis. Mice and many other animals have both of these characteristics, and humans do not.
"This switch controls the expression of a key gene that's required for the formation of these structures," said David Kingsley, a study co-author at Stanford University. "If you kill that gene -- smash the lightbulb -- which has been done previously in mouse genetics, the whiskers don't grow as much and the penile spines fail to form at all."
Humans have kept the "light bulb," however -- we have androgen receptors, but ours don't produce whiskers or penile spines, he said. Chimpanzees do have small sensory whiskers, not as externally obvious as in cats or mice, but we don't have them at all.
To sum up: Humans lack a switch in the genome that would "turn on" penile spines and sensory whiskers. But our primate relatives, such as chimpanzees, have the switch, and that's why they differ from us in these two ways.
And humans are somewhat exceptional in this regard -- a lot of male primates have bumpy penises; mice, which are rodents, have them, too.
The basic idea of natural selection is that over many generations, an animal species loses some traits that are disadvantageous to survival or reproduction (or just don't do much, in some cases), and develops features that carry benefits. Traits that allow members of a species to have more children will eventually become more widespread, as they are passed on genetically to more and more offspring. In humans, this process takes place over hundreds of thousands to millions of years. So, there must be a good reason that the guys you know look different.
In fact, speculation abounds about what purpose the spines serve. One theory is that they are used in sperm competition; if the male's goal is to get his mate pregnant, he will want to take out her previous partner's sperm if she's recently had sex. The bumpy penis may be better for removing that sperm from the female, scientists theorize.
There's probably less debate about why humans reap benefits from having larger brains than chimpanzees, Kingsley said.
The other "switch" examined in this study probably has to do with the expansion of brain regions in humans. Kingsley and colleagues believe they have found a place in their genome comparisons where the loss of DNA in humans may have contributed to the gain of neurons in the brain. That is to say, when humans evolved without a particular switch, the absence of that switch allowed the brain to grow further.
The earliest human ancestors probably had sensory whiskers, penile spines and small brains, Kingsley said. Evolutionary events to remove the whiskers and spines and enlarge the brain probably took place after humans and chimpanzees split apart as separate species (Some 5 million to 7 million years ago), but before Neanderthals and humans diverged (about 600,000 years ago), Kingsley said
We know that Neanderthals had big brains like ours. They probably didn't have penile spines, either. There are traces of the Neanderthal genome in humans today, meaning Neanderthals and humans probably mated.
"The fact that Neanderthals were also missing penile spines is at least consistent with the idea that the mating structures of Neanderthals and modern humans were compatible enough that some interbreeding occurred," Kingsley said.How the human penis lost its spines
By Elizabeth Landau, CNN
March 9, 2011 6:00... more
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Scientists have discovered what could be the first step towards a DNA test to detect the early signs of bowel cancer.
link: http://www.bbc.co.uk/news/health-12637096Scientists have discovered what could be the first step towards a DNA test to detect... more
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Vive la différence? Not at the level of DNA. Men must increase gene expression on their lone X-chromosome to match the two X's possessed by women. A new study explains just how men manage to do that.
link: http://www.sciencedaily.com/releases/2011/03/110302131842.htmVive la différence? Not at the level of DNA. Men must increase gene expression... more
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Two recent news items indicate the Nazification of America continues apace.
First, a report in The Daily broke the news that the Department of Homeland Security plans to begin testing portable DNA scanners this summer.
The device resembles a desktop printer and will make genetic tests common and affordable.
“This can be done in real time, with no technical expertise,” Richard Selden, the executive chairman of NetBio, the company that devised the scanners, told The Daily. That’s perfect for use by the morons, simpletons and thieves DHS hires as its field agents.
http://www.personalliberty.com/conservative-politics/the-nazification-of-america/?eiid=&rmid=2011_03_02_PLA_[P11358471]&rrid=376034956Two recent news items indicate the Nazification of America continues apace.
First, a... more
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A tiny, remote Ecuadorian village has had a rough lot, you might think. They're dwarfs, descended from a lineage of Portuguese and Spanish Sephardic Jews, coerced into Christian conversion and then persecuted by the Inquisition. The upshot? They don't get cancer or diabetes. They're afflicted with what's known as Laron syndrome—the genetic mutation responsible for their tiny size (below 3.5 feet, on average). But this same mutation also robs the villagers of a cellular receptor responsible for pumping out growth hormone—and it's this robbery, the New York Times reports, that simultaneously makes them immune to both cancer and diabetes. After 24 years of study by an Ecuadorian doctor, the 99 tracked villagers came down with startlingly few cases of either ailment. "I discovered the population in 1987," explains Dr. Guevara-Aguirre. "In 1994, I noticed these patients were not having cancer compared with their relatives." The obvious effect of growth hormone deficiency is—yes-not growing. That's why they're dwarves. But their cells have superpowers.
Superpower cells
When researchers applied a genetic serum derived from the Laron villagers to cells in a petri dish, they observed two incredible effects—it acted as a shield against artificial damage. And when damage did occur, the the cells self-destructed—heading off the proliferation of faulty cells that leads to the growth of cancer.So what does this mean for the rest of us? Great things, maybe. Lowered levels of growth hormone could be the key to longer life—mice bred by Ohio University have similarly impaired receptors are living 40% longer than their peers. In fact, the oldest mouse in scientific history nearly reached five years—and had a defective growth hormone gene, just like the Ecuadorian villagers.Now, mice are mice. And we're not mice. But the more we understand about our bodies and why they (inevitably) break, the more we can do to stop it. Or at least slow it. My only question is...if I am going to have to shrink to 3.5ft where can I get good fitting skinny jeans...
Source: http://uk.gizmodo.com/5762524/ecuadorian-genetic-mutants-are-immune-to-cancer
A tiny, remote Ecuadorian village has had a rough lot, you might think.... more
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Nearly 20 percent of the nonhuman genomes held in computer databases are contaminated with human DNA, presumably from the researchers who prepared the samples, say scientists who chanced upon the finding while looking for a human virus.
The affected species include crop plants and the model organisms used in many research laboratories, like the C. elegans roundworm and the Xenopus frog, say three researchers at the University of Connecticut, Mark S. Longo, Michael O’Neill and Rachel O’Neill. Their report was published Wednesday in the journal PLoS One.
The contamination may mislead researchers who assume that any genome sequence in a major databank is highly accurate. Rachel O’Neill said the problem is likely to become more serious in the future as individual human genomes are sequenced for medical reasons. Contamination of human samples by other human DNA is very hard to distinguish from normal variation, and could lead to erroneous medical decisions.
“The level of contamination found in these databases is significant and worrisome,” the researchers write.
They examined genomic data deposited at two of the major databases used by the world’s scientists, the National Center for Biotechnology Information, which is part of the National Institutes of Health, and the European genomic database known as Ensembl.
In the American database, contaminant human DNA is found in 11 percent of assembled genomes, and in 22 percent of the raw data, known as traces, from which the full genome sequence is assembled. At Ensembl, 29 percent of the nonhuman genomes include previously unrecognized human DNA sequence.
Researchers often rely on the traces as accurate because they carry no warning, even though experts know them to be less so, Rachel O’Neill said.
The Connecticut researchers had set out to scan the public databases for a human virus that might have infected other species by inserting its own DNA into their genomes. They found so much human-looking DNA in nonhuman genomes that contamination seemed the likeliest explanation. People shed DNA all the time from dead skin cells and other sources, and it is easy to contaminate DNA samples unless special precautions are taken.
Dr. O’Neill said they then decided to do a specific search for human contamination by looking for a common human sequence called AluY. The sequence is less than 300 DNA units in length, but occurs one million times in the human genome.
She was surprised to find extensive contamination with AluY not only in the raw data but also in the complete genomes. Computers assemble genomes by matching overlapping fragments, and so should exclude any extraneous DNA. “The fact we find it in so many assemblies is the shock,” Dr. O’Neill said.
Another problem is that most DNA sequencing now uses a fast, cheap technology that matches fragments of DNA to the reference genomes already in the databanks, assuming they are fully accurate. This method, called resequencing, gives the computer assembly algorithms much less chance of catching contamination.
Dr. David Lipman, director of the National Center for Biotechnology Information, said that the center now screens all genomic data submitted to it for contaminant DNA. Screening for animal and plant contaminants started in 2008, and screens against contaminating bacterial DNA were added in 2009.
Asked why screening was not in place from the beginning, Dr. Lipman said that at first only the large, government-supported DNA sequencing centers were capable of sequencing whole genomes, and they took care of the contamination problem. As the technology became more widespread, his center instituted its own screens.
“We don’t see the contamination she’s talking about,” he said.
Richard Gibbs, director of the Human Genome Sequencing Center at the Baylor College of Medicine, said that cross-species contamination “often occurs” and was easier for computers to filter out with the older sequencing methods. He said the PLoS One report did not add much new. “I don’t know of any good scientific work that has been compromised by cross-species contamination,” he said.
Dr. O’Neill said she just wished to alert people to the problem and was not calling on the curators of national databases to do anything differently. Because the contamination is so extensive, it has probably being going on for a decade, not just recently, she said.
“I’m very nervous,” she said. “I’m nervous that this paper will make some people unhappy, and I’m also nervous that some people won’t pay attention to it.”Nearly 20 percent of the nonhuman genomes held in computer databases are contaminated... more
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JoAnn Stephens, 43-year-old former physical education teacher at the Mineola elementary and middle schools in Mineola, Texas , has been arrested for an improper relationship with a student.
The alleged sexual encounters took place between Stephens and a 15-year-old male student, in May of 2008 at Lake Holbrook, in Mineola. DNA samples found in a truck links the student to the accused female teacher.
Court documents allege Stephens had a relationship with the student for years, keeping in contact through text and phone conversations. Police say Stephens also provided the student with a cell phone, bought him candy, gifts, clothes and money.
http://sexcrimewatch.blogspot.com/2011/02/former-diboll-coach-arrested-for.htmlJoAnn Stephens, 43-year-old former physical education teacher at the Mineola... more
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Improved gene tests can now reveal children born of incest without the need to test for either parent's DNA, doctors report Thursday.
link :http://yourlife.usatoday.com/health/medical/story/2011/02/DNA-tests-could-reveal-unknown-proof-of-incest/43577514/1Improved gene tests can now reveal children born of incest without the need to test... more
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NEW YORK (GenomeWeb News) – An independent group that provides scientific advice to the US Department of Defense has suggested that DoD start collecting and making plans to use personal genomic data in its health care programs and in making some of its personnel decisions.NEW YORK (GenomeWeb News) – An independent group that provides scientific advice... more
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When a Gilbert police detective interviewed John Watkins as a suspect in a 2003 rape investigation, his message to Watkins was clear.
"There was DNA recovered," the detective told Watkins. "What I'm getting at is: DNA is black and white."
It took nearly seven years for that DNA to be tested - years Watkins spent in prison.
Last month, about halfway through a 14-year sentence, Watkins was released from prison in part because the test results showed the DNA did not belong to him. Nonetheless, police and prosecutors are not convinced they charged the wrong man, and they now insist that DNA evidence is not "black and white," but more a shade of gray.
Watkins' release, which came after his case was put under a microscope by the Arizona Justice Project, has rekindled the debate over police interrogation tactics and whether DNA testing is an infallible criminal investigative tool.
Read more: http://www.azcentral.com/arizonarepublic/local/articles/2011/01/23/20110123rape-john-watkins-dna.html#ixzz1Buti7MPmWhen a Gilbert police detective interviewed John Watkins as a suspect in a 2003 rape... more
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Today Australian News website have published an article with headline "Tatooine's twin suns - coming to a planet near you just as soon as Betelgeuse explodes" according to it - Yes, any day now we see a second sun light up the sky, if only for a matter of weeks.Today Australian News website have published an article with headline... more
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ScienceDaily (Jan. 7, 2011) — A new University of Florida study following the evolution of lice shows modern humans started wearing clothes about 170,000 years ago, a technology which enabled them to successfully migrate out of Africa.
Principal investigator David Reed, associate curator of mammals at the Florida Museum of Natural History on the UF campus, studies lice in modern humans to better understand human evolution and migration patterns. His latest five-year study used DNA sequencing to calculate when clothing lice first began to diverge genetically from human head lice.
Funded by the National Science Foundation, the study is available online and appears in this month's print edition of Molecular Biology and Evolution.
"We wanted to find another method for pinpointing when humans might have first started wearing clothing," Reed said. "Because they are so well adapted to clothing, we know that body lice or clothing lice almost certainly didn't exist until clothing came about in humans."
The data shows modern humans started wearing clothes about 70,000 years before migrating into colder climates and higher latitudes, which began about 100,000 years ago. This date would be virtually impossible to determine using archaeological data because early clothing would not survive in archaeological sites.
The study also shows humans started wearing clothes well after they lost body hair, which genetic skin-coloration research pinpoints at about 1 million years ago, meaning humans spent a considerable amount of time without body hair and without clothing, Reed said.
"It's interesting to think humans were able to survive in Africa for hundreds of thousands of years without clothing and without body hair, and that it wasn't until they had clothing that modern humans were then moving out of Africa into other parts of the world," Reed said.
Lice are studied because unlike most other parasites, they are stranded on lineages of hosts over long periods of evolutionary time. The relationship allows scientists to learn about evolutionary changes in the host based on changes in the parasite.
Applying unique data sets from lice to human evolution has only developed within the last 20 years, and provides information that could be used in medicine, evolutionary biology, ecology or any number of fields, Reed said.
"It gives the opportunity to study host-switching and invading new hosts -- behaviors seen in emerging infectious diseases that affect humans," Reed said.
A study of clothing lice in 2003 led by Mark Stoneking, a geneticist at the Max Planck Institute in Leipzig, Germany, estimated humans first began wearing clothes about 107,000 years ago. But the UF research includes new data and calculation methods better suited for the question.
"The new result from this lice study is an unexpectedly early date for clothing, much older than the earliest solid archaeological evidence, but it makes sense," said Ian Gilligan, lecturer in the School of Archaeology and Anthropology at The Australian National University. "It means modern humans probably started wearing clothes on a regular basis to keep warm when they were first exposed to Ice Age conditions."
The last Ice Age occurred about 120,000 years ago, but the study's date suggests humans started wearing clothes in the preceding Ice Age 180,000 years ago, according to temperature estimates from ice core studies, Gilligan said. Modern humans first appeared about 200,000 years ago.
Because archaic hominins did not leave descendants of clothing lice for sampling, the study does not explore the possibility archaic hominins outside of Africa were clothed in some fashion 800,000 years ago. But while archaic humans were able to survive for many generations outside Africa, only modern humans persisted there until the present.
"The things that may have made us much more successful in that endeavor hundreds of thousands of years later were technologies like the controlled use of fire, the ability to use clothing, new hunting strategies and new stone tools," Reed said.
Study co-authors were Melissa Toups of Indiana University and Andrew Kitchen of The Pennsylvania State University, both previously with UF. Co-author Jessica Light of Texas A&M University was formerly a post-doctoral fellow at the Florida Museum. The researchers completed the project with the help of Reed's NSF Faculty Early Career Development Award, which is granted to researchers who exemplify the teacher-researcher role.ScienceDaily (Jan. 7, 2011) — A new University of Florida study following the... more
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Houston Man To Be Declared Innocent After Serving 30 Years For a Dallas Rape and Robbery He Didn’t Commit
[Print Version]
Innocence Project Urges State to Pass Legislation that Would Help Prevent Misidentification
UPDATE: January 4, 2011 – A Texas judge this morning declared Cornelius Dupree an innocent man, clearing him more than 30 years after he was wrongfully convicted. Read more about today’s hearing on the Innocence Blog and get the details on Dupree’s case below.
(DALLAS, TX; Monday, January 3, 2011) With the consent of the District Attorney’s Office, a Dallas County judge is expected to vacate the rape and robbery conviction of Cornelius Dupree, Jr. on Tuesday, January 4, and declare him an innocent man after he served 30 years for crimes he didn’t commit. DNA tests requested by the Innocence Project and pursued by the Dallas District Attorney’s Conviction Integrity Unit proved that he could not have been involved in the crime. Dupree served more time in prison than any other person in Texas who was later cleared through DNA testing. The hearing will take place on Tuesday, January 4, 2011, at 9:00 a.m. CST in Criminal District Court 2 before Judge Don Adams.
“Cornelius Dupree spent the prime of his life behind bars because of mistaken identification that probably would have been avoided if the best practices now used in Dallas had been employed,” said Barry Scheck, Co-Director of the Innocence Project, which is affiliated with Cardozo School of Law. “Yet most counties in Texas do not have these best practices in place. This must be remedied in the next legislative session by the adoption of an eyewitness identification reform bill that had the votes needed for passage last session but not enough time to get enacted. Let us never forget that, as in the heartbreaking case of Cornelius Dupree, a staggering 75% of wrongful convictions of people later cleared by DNA evidence resulted from misidentifications.”
On November 23, 1979, two men approached a 26-year-old female and her male friend in the parking lot of a drive-in grocery and forced them into the male victim’s car at gunpoint. The male victim was forced to drive them in his car, during which time the perpetrators robbed both victims of their money and personal property. The perpetrators forced the male to pull over at a highway exit and ordered him out of the vehicle. They continued on to a nearby park where both perpetrators raped the victim.
On December 1, 1979, Dupree, 19, and a friend named Anthony Massingill were on their way to a party when they were stopped and frisked approximately two miles from the drive-in grocery where the crime began. Police recovered a handgun from Massingill and placed the two men under arrest. The following day, the female victim selected Dupree’s and Massingill’s photographs from a photo array. The male victim, however, was unable to identify either defendant in the same photo array. At the identification hearing and trial, which took place approximately four months after the attack, both victims identified Dupree and Massingill in court as their attackers. During the identification hearing, however, the female victim repeatedly misidentified a photo of Massingill as Dupree before finally identifying it as Dupree’s photograph. The victims are both white and both Dupree and Massingill are black.
Throughout the trial and since, Dupree has maintained his innocence. His defense at trial was misidentification. However, he and Massingill were both found guilty of aggravated robbery with a deadly weapon on April 3, 1980. Dupree was sentenced to 75 years in prison. The prosecutors ultimately chose not to pursue the rape charges because a conviction would not have resulted in additional jail time. Dupree appealed his conviction several times, but these efforts were unsuccessful.
He eventually sought the help of the Innocence Project, which requested that the Dallas Country District Attorney’s Office initiate a search for the physical evidence in Dupree’s case. On July 6, 2007, the Innocence Project learned that pubic hair combings and cuttings that were taken from the female victim during the female victim’s medical examination immediately following the rape were available. With the state’s consent, the Innocence Project conducted DNA testing of the evidence, which found the presence of sperm from two males that did not match the DNA of either Dupree or Massingill. The DA’s office agrees with the Innocence Project that the DNA test results establish that Dupree and Massingill are actually innocent of the robbery and is fully supporting the application for habeas corpus relief in court.
Massingill, who is represented by the Texas Wesleyan Innocence Project, will not be participating in tomorrow’s hearing but is expected to be declared innocent at a later date. At the same time Massingill was misidentified in the 1979 rape and robbery for which DNA has now proven his and Dupree’s innocence, he was also charged with and convicted of another rape for which he remains incarcerated. Massingill also maintains his innocence of the second crime, in which DNA testing is scheduled to begin shortly.
“Mistaken identification has always plagued the criminal justice system, but great strides have been made in the last three decades to understand the problem and come up with fixes like those being considered by the state Legislature that help minimize wrongful convictions,” said Nina Morrison, Senior Staff Attorney at the Innocence Project. “We hope state lawmakers take note of the terrible miscarriage of justice suffered by Cornelius. When the wrong person is convicted of a crime, the real perpetrator goes free, harming everyone.”
SB 121, authored by Sen. Ellis, and HB 215, authored by Rep. Gallego, would require all law enforcement agencies to adopt written policies for identification procedures, including lineups and photo arrays such as the one used in Dupree’s case. These procedures must be based on scientific research on eyewitness memory to increase accuracy and reliability and must include instructions to witnesses, documentation and preservation of witness statements and identification procedures as well as procedures for assigning lineup and photo array administrators to prevent opportunities to influence the witness.
After serving 30 years of his 75-year sentence, Dupree was released from prison on July 22, 2010, and placed on parole. After initial DNA testing completed on July 30, 2010 - less than two weeks after his release - indicated he was likely innocent of the rape and robbery, the District Attorney’s Office agreed not to oppose a request by the Innocence Project made to the Board of Pardons and Paroles that Dupree should no longer have to comply with several conditions placed on his parole, including registering and participating in therapy for sex offenders. That request was granted by the Board in October. Additional testing completed in December confirmed that Dupree and Massingill were wrongly convicted.
Dupree is represented by Innocence Project attorneys Scheck and Morrison as well as Robert C. Hinton of Dallas. He is pictured above with his wife Selma Perkins Dupree. The couple was married shortly after Dupree’s release in 2010.Houston Man To Be Declared Innocent After Serving 30 Years For a Dallas Rape and... more
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Evolution's "new twist": Neanderthal-like "sister group" bred with humans like us.
Ker Than
for National Geographic News
Published December 22, 2010
A previously unknown kind of human—the Denisovans—likely roamed Asia for thousands of years, probably interbreeding occasionally with humans like you and me, according to a new genetic study.
In fact, living Pacific islanders in Papua New Guinea may be distant descendants of these prehistoric pairings, according to new analysis of DNA from a girl's 40,000-year-old pinkie bone, found in Siberian Russia's Denisova cave.
This "new twist" in human evolution adds substantial new evidence that different types of humans—so-called modern humans and Neanderthals, modern humans and Denisovans, and perhaps even Denisovans and Neanderthals—mated and bore offspring, experts say.
"We don't think the Denisovans went to Papua New Guinea," located at the northwestern edge of the Pacific region called Melanesia, explained study co-author Bence Viola, an anthropologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
(Full story at link)Evolution's "new twist": Neanderthal-like "sister group" bred... more
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ScienceDaily (Dec. 22, 2010) — A 30,000-year-old finger bone found in a cave in southern Siberia came from a young girl who was neither an early modern human nor a Neanderthal, but belonged to a previously unknown group of human relatives who may have lived throughout much of Asia during the late Pleistocene epoch. Although the fossil evidence consists of just a bone fragment and one tooth, DNA extracted from the bone has yielded a draft genome sequence, enabling scientists to reach some startling conclusions about this extinct branch of the human family tree, called "Denisovans" after the cave where the fossils were found
The findings are reported in the Dec. 23 issue of Nature by an international team of scientists, including many of the same researchers who earlier this year published the Neanderthal genome. Coauthor Richard Green of the University of California, Santa Cruz, played a lead role in the analysis of the genome sequence data, for which a special portal was designed on the UCSC Genome Browser. The team was led by Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
By comparing the Denisovan genome sequence with the genomes of Neanderthals and modern humans, the researchers determined that the Denisovans were a sister group to the Neanderthals, descended from the same ancestral population that had separated earlier from the ancestors of present-day humans. The study also found surprising evidence of Denisovan gene sequences in modern-day Melanesians, suggesting that there was interbreeding between Denisovans and the ancestors of Melanesians, just as Neanderthals appear to have interbred with the ancestors of all modern-day non-Africans.
"The story now gets a bit more complicated," said Green, an assistant professor of biomolecular engineering in the Baskin School of Engineering at UC Santa Cruz. "Instead of the clean story we used to have of modern humans migrating out of Africa and replacing Neanderthals, we now see these very intertwined story lines with more players and more interactions than we knew of before."
The Denisovans appear to have been quite different both genetically and morphologically from Neanderthals and modern humans. The tooth found in the same cave as the finger bone shows a morphology that is distinct from Neanderthals and modern humans and resembles much older human ancestors, such as Homo habilis and Homo erectus. DNA analysis showed that the tooth and the finger bone came from different individuals in the same population.
The finger bone was found in 2008 by Russian scientists in Denisova Cave, an archaeological site in southern Siberia. Pääbo, who had worked with the Russian scientists before, obtained the bone for his research on ancient DNA. In Leipzig, researchers extracted DNA from the bone and sequenced the mitochondrial genome, a smaller DNA sequence separate from the chromosomal DNA and easier to obtain from ancient samples. The results, published earlier this year, showed a surprising divergence from the mitochondrial genomes of Neanderthals and modern humans, and the team quickly began working to sequence the nuclear genome.
"It was fortuitous that this discovery came quickly on the heels of the Neanderthal genome, because we already had the team assembled and ready to do another similar analysis," Green said. "This is an incredibly well-preserved sample, so it was a joy to work with data this nice. We don't know all the reasons why, but it is almost miraculous how well-preserved the DNA is."
The relationship between Denisovans and present-day Melanesians was a completely unexpected finding, he said. The comparative analysis, which included genome sequences of individuals from New Guinea and Bougainville Island, indicates that genetic material derived from Denisovans makes up about 4 to 6 percent of the genomes of at least some Melanesian populations. The fact that Denisovans were discovered in southern Siberia but contributed genetic material to modern human populations in Southeast Asia suggests that their population may have been widespread in Asia during the late Pleistocene, said David Reich of Harvard Medical School, who led the population genetic analysis.
It is not clear why fossil evidence had not already revealed the existence of this group of ancient human relatives. But Green noted that the finger bone was originally thought to be from an early modern human, and the tooth resembles those of other ancient human ancestors. "It could be that other samples are misclassified," he said. "But now, by analyzing DNA, we can say more definitively what they are. It's getting easier technically to do this, and it's a great new way to extract information from fossil remains."
In the light of the Neanderthal and Denisovan genomes, a new, more complex picture is emerging of the evolutionary history of modern humans and our extinct relatives. According to Green, there was probably an ancestral group that left Africa between 300,000 and 400,000 years ago and quickly diverged, with one branch becoming the Neanderthals who spread into Europe and the other branch moving east and becoming Denisovans. When modern humans left Africa about 70,000 to 80,000 years ago, they first encountered the Neanderthals, an interaction that left traces of Neanderthal DNA scattered through the genomes of all non-Africans. One group of humans later came in contact with Denisovans, leaving traces of Denisovan DNA in the genomes of humans who settled in Melanesia.
"This study fills in some of the details, but we would like to know much more about the Denisovans and their interactions with human populations," Green said. "And you have to wonder if there were other populations that remain to be discovered. Is there a fourth player in this story?"
The paper's 28 coauthors include scientists from Germany, Spain, China, Russia, Canada, and the United States. Reich and Green are among seven coauthors credited with contributing equally to this work. This research was supported by the Max Planck Society, the Krekeler Foundation, the U.S. National Institutes of Health, and the U.S. National Science
http://www.sciencedaily.com/releases/2010/12/101222131119.htmScienceDaily (Dec. 22, 2010) — A 30,000-year-old finger bone found in a cave in... more
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Scientists have identified an embalmed head as belonging to King Henri IV of France, who was assassinated in 1610 at the age of 57.The head was lost after revolutionaries ransacked a royal chapel near Paris in 1793.It has taken the researchers nine months to identify the late monarch's embalmed head. A lesion near his nose, a pierced ear and a healed facial wound - from a previous assassination attempt - were among the marks that helped identify the head. The results was published today in the medical journal, BMJ.King Henri IV was one of France's favourite monarchs.He converted to Catholicism to end France's wars of religion, declaring "Paris is worth a Mass", but was later killed by a Catholic fundamentalist.He built the Pont Neuf bridge and the Place des Vosges in Paris. Henri was the first of the Bourbon line of monarchs, which included his grandson Louis XIV, the Sun King.His head will now be reinterred in the Basilica of Saint Denis after a national Mass and funeral next year.
Scientists have identified an embalmed head as belonging to King Henri IV of France,... more
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