上海北桥鸡2020 Tag Archive
A preliminary draft of the genome of the Neanderthal, our closest evolutionary relative, reveals in exquisite detail how this long-extinct member of the Homo genus relates to modern humans.The work for the project was carried out in two phases. In the first phase, scientists at the Max Planck Institute in Leipzig, Germany extracted a genome’s worth of DNA from bonesapproximately 40,000 years old, taken from a cave in Croatia. In the second phase, an international consortium analyzed the data to study how Neanderthals are related genetically to modern humans. A key analysis — led by Harvard Medical School (HMS) associate professor of genetics David Reich — revealed that Neanderthals interbred with ancestors of modern Europeans and Asians, but not Africans.“Europeans and East Asians today bear a closer relationship to Neanderthals than do Africans,” says Reich. “One to four percent of the genomes of non-Africans trace their ancestry to Neanderthals. Europeans and Asians both have this signal, indicating that the gene flow occurred at least 45,000 years ago, before these two populations’ ancestors separated.”These findings are published in the May 6 issue of Science.From ancient ancestors . . .Neanderthals, who became extinct roughly 30,000 years ago for unknown reasons, and who diverged from modern human ancestors 270,000-440,000 years ago, have long been a subject of intense speculation. They are the closest population in the fossil record to anatomically modern humans, yet they are clearly distinct in terms of their physical structure.Neanderthals had bigger faces than we do, with more barrel-shaped chests and shorter limbs, and were most likely better adapted to colder climates. Their brains, despite being a bit longer with possibly smaller temporal lobes, were generally the same size as ours.The fossil record shows that modern humans and Neanderthals overlapped geographically for tens of thousands of years in Europe and Asia. From this evidence springs the obvious question: Did the two species intermingle and pool their genes?. . . to distant cousinsFor more than a decade, a group of researchers led by Svante Pääbo at the Max Planck Institute has been attempting to obtain sequences from the Neanderthal genome using pill-sized samples of powder extracted from bone fragments. This type of work is often thwarted by sample contamination (the majority of DNA extracted in such experiments turns out to come from microbes, or from a hapless laboratory technician). However, the researchers increased the purity of their samples by taking advantage of technological advances that could both detect and filter out contamination of the genetic material.The result was a reconstruction of more than 4 billion base pairs of DNA assembled from a variety of cells. This total represents roughly 60 percent of the Neanderthal genome.An international team of geneticists led by David Reich then studied how Neanderthals and modern humans are related by comparing this new genomic data to five present-day humans from far-flung regions of the world. Reich and his colleagues discovered that roughly one to four percent of the genomes of all non-African modern humans are directly descended from the Neanderthal. What’s more, these modern groups all appear equally related to their “distant” cousins.One explanation for this uniform genetic distribution is that interbreeding occurred at the gateway of the migration of modern humans out of Africa in the upper Paleolithic period, roughly 45,000 years ago. From points in Northern Africa—that is, modern-day countries such as Libya and Egypt—modern humans dispersed throughout Europe and East Asia.“That’s not the only explanation, but it’s the most likely one,” says Reich.As far as the researchers can tell, this small percentage of inherited DNA is random. There is no evidence that it is associated with specific traits.According to Harvard University professor of human evolutionary biology Daniel Lieberman, who was not involved with the study, we shouldn’t be terribly surprised at this evidence of interbreeding. “I do not think this in any way lessens the evidence that Neanderthals and modern humans were indeed separate species. Closely related species often do interbreed to a limited extent.”Clearly, the data is a treasure trove for future study. “There is a tremendous amount of yet untapped information in this genome,” says Reich, “and we’re going to bespending many more decades getting closer to what it all means.”
“Walk anything you don’t like,” he said.“This is as good as it gets. We know the river well, and are willing to go your pace. Besides, you warmed up on the upper,” he said.The flow was even lower than normal summer flow and for years I yearned to see if the Green Narrows lived up to its reputation. Over the years, other paddlers told me that if I loved living in Western North Carolina now, just wait until I got on the Green. “It gets so much better,” they said.I followed them past the take-out for the Upper, feeling wobbly and terrified.We eddied out above Bride of Frankenstein and they told me the line. When I got to the bottom, I was wide-eyed and gripped.Rocks stood like sentries, guarding the river below. I strained to see a break between them, large enough to squeeze my kayak between. I reminded myself that I had to have faith – in my paddling skills, in my friends, in my ability to react in the moment.I felt like my stomach twisted into a pretzel every time I scouted a rapid. Cloaked in the shadows of the canopy, the dark lent even more mystery to the river.From there until after Rapid Transit, paddling turned into a day hike with my kayak. I carried, dragged and pushed my kayak around huge rhododendron bushes and through poison ivy.I met my friends above Sunshine and paddled from river left to river right where we all walked.At the bottom, he reminded me. “Look back up, that’s a big part of why we’re here.”A boulder glowed as the sun hit it at almost a right angle. Glimmers of green skipped across the river, making it appear alive. Light filled every crevice of the river, turning the water a transparent shade of green.We stood there, shoulder-to-shoulder in admiration.“Wow,” I said, as soon as the word tumbled out I wished I had a better word to express the beauty of being there, in this place sacred for so many paddlers with good friends.They nodded.I relaxed, realizing there’s wonder in the obvious. I wasn’t the first paddler to see this view. Heck, I wasn’t even paddling most of the river. But through a series of conditions it all lined up that I got to be there, that for that moment I witnessed the sunshine lighting up the river and limitations lifted.I lingered on the rock a little longer, letting all that brightness seep in, opening myself of to dreams and remembering possibility.
A trail of pill bottles stolen from a Florida pharmacy led detectives to a home where they found two men who matched descriptions of the robbers seen on surveillance video.According to officials with the Pinellas County Sheriff’s Office, the duo and an accomplice robbed a CVS in Clearwater at around 5 a.m. on New Year’s Day at gunpoint. They also bound the employees with zip ties.The robbers got away with more than 10,000 pills containing the opioids hydrocodone and oxycodone, the Tampa Bay Times reports. Those drugs had a street value of about $320,000.However, the men left behind some important clues.The surveillance video captured them fleeing in a white Chrysler 200. They also emptied pills from bottles, which they threw from the car’s window, creating a trail which guided detectives to the home.Investigators believe the trio planned the robbery, going as far as to stake out the location out the day before, according to The Times. Detectives noticed one of the robbers casing the store in the surveillance video they reviewed.The two men, 19-year-old Christopher Rachell Jr. and 19-year-old David Dobbins, were arrested later New Year’s Day.Dobbins’ cellphone contained video of the men in a room with a bed that was piled with pills and clear plastic bags, reports add. Other videos show them handling a white garbage bag, which is the same kind seen in the pharmacy’s surveillance video.The videos also helped investigators to identify the accomplice, 18-year-old Roy Lampkin, who can be seen handling the white bag. Detectives also found his fingerprints at the scene.Lampkin was seen on video entering the CVS at 3:52 a.m. on Jan. 1, apparently asking the pharmacist a question. Authorities caught up to him on Feb. 5 and charged him with drug trafficking.All three men are still in jail.Rachell and Dobbins are each charged with two counts of trafficking in illegal drugs, three counts of false imprisonment and one count of armed robbery.Dobbins is being held in lieu of $280,000 bond. Rachell is also charged with oxycodone possession and is being held in lieu of $282,000 bond, while Lampkin is charged with two drug trafficking charges and remains behind bars on a $1 million bond.