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   From: mmike@msu.edu   
      
   Anyone with any intelligence knows "africans" don't have any,   
   and aren't considered humans.   
      
   The existence of a mysterious ancient human lineage and the   
   genetic changes that separate modern humans from their closest   
   extinct relatives are among the many secrets now revealed in the   
   first high-quality genome sequence from a Neanderthal woman,   
   researchers say.   
      
   The Neanderthal woman whose toe bone was sequenced also reveals   
   inbreeding may have been common among her recent ancestors, as   
   her parents were closely related, possibly half-siblings or   
   another near relation.   
      
   Although modern humans are the world's only surviving human   
   lineage, others also once lived on Earth. These included   
   Neanderthals, the closest extinct relatives of modern humans,   
   and the relatively newfound Denisovans, whose genetic footprint   
   apparently extended from Siberia to the Pacific islands of   
   Oceania. Both Neanderthals and Denisovans descended from a group   
   that diverged from the ancestors of all modern humans. [See   
   Photos of Neanderthal Bone & Denisovan Fossils]   
      
   The first signs of Denisovans came from a finger bone and a   
   molar tooth discovered in Denisova Cave in southern Siberia in   
   2008. To learn more about Denisovans, scientists examined a   
   woman's toe bone, which was unearthed in the cave in 2010 and   
   showed physical features resembling those of both Neanderthals   
   and modern humans. The fossil is thought to be about 50,000   
   years old, and slightly older than previously analyzed Denisovan   
   fossils.   
      
   Human interbreeding   
      
   The scientists focused mostly on the fossil's nuclear DNA, the   
   genetic material from the chromosomes in the nucleus of the cell   
   that a person receives from both their mother and father. They   
   also examined the genome of this fossil's mitochondria — the   
   powerhouses of the cell, which possess their own DNA and get   
   passed down solely from the mother.   
      
   The investigators completely sequenced the fossil's nuclear DNA,   
   with each position (or nucleotide) sequenced an average of 50   
   times. This makes the sequence's quality at least as high as   
   that of genomes sequenced from present-day people.   
      
   The genetic analysis revealed the toe bone belonged to a   
   Neanderthal. When compared with other Neanderthal mitochondrial   
   DNA samples, this newfound fossil's closest known relatives are   
   Neanderthals found in Mezmaiskaya Cave in the Caucasus Mountains   
   about 2,100 miles (3,380 kilometers) away.   
      
   These findings helped the scientists refine the human family   
   tree, further confirming that different human lineages   
   interbred. They estimated about 1.5 to 2.1 percent of DNA of   
   people outside Africa are Neanderthal in origin, while about 0.2   
   percent of DNA of mainland Asians and Native Americans is   
   Denisovan in origin.   
      
   "Admixture seems to be common among human groups," said study   
   lead author Kay Prüfer, a computational geneticist at the Max   
   Planck Institute for Evolutionary Anthropology in Leipzig,   
   Germany.   
      
   Intriguingly, the scientists discovered that apparently   
   Denisovans interbred with an unknown human lineage, getting as   
   much as 2.7 to 5.8 percent of their genomes from it. This   
   mystery relative apparently split from the ancestors of all   
   modern humans, Neanderthals and Denisovans between 900,000 years   
   and 4 million years ago, before these latter groups started   
   diverging from each other.   
      
   This enigmatic lineage could even potentially be Homo erectus,   
   the earliest undisputed predecessor of modern humans. There are   
   no signs this unknown group interbred with modern humans or   
   Neanderthals, Prüferadded. [The 10 Biggest Mysteries of the   
   First Humans]   
      
   "Some unknown archaic DNA might have caught a ride through time   
   by living on in Denisovans until we dug the individual up and   
   sequenced it," Prüfertold LiveScience. "It opens up the prospect   
   to study the sequence of an archaic (human lineage) that might   
   be out of reach for DNA sequencing."   
      
   Interbreeding took place between Neanderthals and Denisovans as   
   well. These new findings suggest at least 0.5 percent of the   
   Denisovan genome came from Neanderthals. However, nothing of the   
   Denisovan genome has been detected in Neanderthals so far.   
      
   In addition, "the age of the Neanderthals and Denisovans we   
   sequenced also doesn't allow us to say whether any gene flow   
   from modern humans to Neanderthals or Denisovans happened,"   
   Prüfer said. The Neanderthals and Denisovans that researchers   
   have sequenced the DNA of to date "probably lived at a time when   
   no modern humans were around," he explained.   
      
   Modern humans' distinguishing features   
      
   It remains uncertain when modern humans, Neanderthals and   
   Denisovans diverged from one another. The researchers currently   
   estimate modern humans split from the common ancestors of all   
   Neanderthals and Denisovans between 550,000 and 765,000 years   
   ago, and Neanderthals and Denisovans diverged from each other   
   between 381,000 and 473,000 years ago.   
      
   Genetic analysis revealed the parents of the woman whose toe   
   bone they analyzed were closely related — possibly half-   
   siblings, or an uncle and niece, or an aunt and nephew, or a   
   grandfather and granddaughter, or a grandmother and grandson.   
   Inbreeding among close relatives was apparently common among the   
   woman's recent ancestors. It remains uncertain as to whether   
   inbreeding was some kind of cultural practice among these   
   Neanderthals or whether it was unavoidable due to how few   
   Neanderthals apparently lived in this area, Prüfer said.   
      
   By comparing modern human, Neanderthal and Denisovan genomes,   
   the researchers identified more than 31,000 genetic changes that   
   distinguish modern humans from Neanderthals and Denisovans.   
   These changes may be linked with the survival and success of   
   modern humans — a number have to do with brain development.   
      
   "If one speculates that we modern humans carry some genetic   
   changes that enabled us to develop technology to the degree we   
   did and settle in nearly all habitable areas on the planet, then   
   these must be among those changes," Prüfer said. "It is hard to   
   say what exactly these changes do, if anything, and it will take   
   the next few years to find out whether hidden among all these   
   changes are some that helped us modern humans to develop   
   sophisticated technology and settle all over the planet."   
      
   Prüfer and his colleagues detailed their findings in the Dec. 19   
   issue of the journal Nature.   
      
       
      
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