Mighty Dons Of Science News

A pre­vi­ously un­known line­age of hu­mans has been iden­ti­fied based on genes ex­tracted from a bit of bone found in Si­be­ria, sci­en­tists say.

The find­ing may rep­re­sent a new spe­cies that lived along­side Ne­an­der­thal peo­ple and an­a­tom­ic­ally “mod­ern” hu­mans in that re­gion, ac­cord­ing to the re­search­ers.

“I at first did­n’t be­lieve” that the re­sult could be pos­si­ble, said one of the re­search­ers in­volved with the find­ing, Svante Pääbo of the Max Planck In­sti­tute for Ev­o­lu­tion­ary An­thro­po­l­ogy, Leip­zig, Ger­ma­ny. How­ev­er, Pääbo said, ge­net­ic test re­sults showed “it’s some new crea­ture that has not been on our ra­dar screen so far.” The find­ings are pub­lished in the March 25 is­sue of the re­search jour­nal  Na­ture.

The con­clus­ions were based on the se­quenc­ing, or de­cod­ing, of the or­gan­is­m’s “mi­to­chon­drial ge­nome,” that is, DNA from a cel­lu­lar struc­tures called the mi­to­chon­dria.

Mi­to­chon­chon­drial DNA is not in­her­it­ed the same way as the rest of an an­i­mal’s DNA, but rath­er is passed down only from the moth­er. Be­cause un­like oth­er DNA it re­mains re­la­tive­ly un­changed when passed down through genera­t­ions, it plays an im­por­tant role in an­ces­try stud­ies, in par­tic­u­lar in de­ter­min­ing an or­gan­is­m’s moth­er-line an­ces­try.

The ge­net­ic se­quenc­ing point­ed to a pre­vi­ously un­known ho­minin, or ex­tinct mem­ber of the hu­man line­age, who lived in the Al­tai moun­tains of south­ern Si­be­ria be­tween 48,000 and 30,000 years ago, said the re­search­ers.

The inves­tigat­ing team, which in­clud­ed al­so re­search­ers from the Un­ited States, Aus­tria and Rus­sia, se­quenced genes from a ti­ny piece of pinky fin­ger bone found in Denisova cave in the Al­tai Moun­tains. They com­pared the mi­to­chon­drial ge­nome with that of mod­ern hu­mans and Ne­an­der­thals.

The anal­y­sis in­di­cat­ed that the crea­ture shared a com­mon fe­male or “mi­to­chon­drial” an­ces­tor with mod­ern hu­man and Ne­an­der­thals about a mil­lion years ago, the sci­en­tists said. That’s about twice as old as what is be­lieved to be the most re­cent com­mon mi­to­chon­drial an­ces­tor of mod­ern hu­mans and Ne­an­der­thals. Ne­an­der­thals were a stocky, now ex­tinct sub­group of our spe­cies, Ho­mo sapi­ens, who lived in Eu­rope and parts of Asia from around 100,000 to 30,000 years ago.

The age of the fos­sil and the lay­ers of earth in which they turned up al­so sug­gest “the Deni­sova ho­minin lived close in time and space with Ne­an­der­thals as well as with mod­ern hu­mans,” the re­search­ers wrote.

Al­though re­search­ers said they lacked de­fin­i­tive enough in­forma­t­ion to de­clare the fos­sil a new spe­cies, they said it al­so likely rep­re­sented a sep­a­rate migra­t­ion out of Af­ri­ca from mod­ern hu­mans and Ne­an­der­thals, both of whom are thought to have orig­i­nat­ed in that con­ti­nent. The in­ves­ti­ga­tors al­so said they have no in­forma­t­ion yet that could serve to phys­ic­ally de­scribe any un­usu­al char­ac­ter­is­tics that the new­found hu­man an­ces­tor might have pos­sessed.

Re­search­ers have identified a chem­i­cal chain of events that leads can­cer cells to age, and thus stop re­pro­duc­ing. By exp­loit­ing this process, they pro­pose, sci­en­tists might be able to de­vel­op new can­cer ther­a­pies.

The mo­lec­u­lar se­quence of events, called a sig­nal­ing path­way, is de­scribed in the March 18 is­sue of the research jour­nal Na­ture by in­ves­ti­ga­tors Pa­o­lo Pan­dolfi of the Har­vard Med­i­cal School and col­leagues.

Can­cer cells are nor­mally able to re­pro­duce them­selves in­def­i­nitely with­out age­ing; this in­deed is a co­re as­pect of the prob­lem con­fronting can­cer vic­tims. The out-of-control cell di­vi­sion leads to the crea­t­ion of an ever-growing load of tu­mors.

The newfound pathway drives cell ag­ing, or “se­nes­cence,” only in can­cerous con­di­tions, according to Pan­dol­fi’s group. A key com­po­nent of the path­way is a gene called Skp2, the sci­en­tists re­ported. By sup­press­ing this gene, they found that they could pro­foundly re­strict tu­mor forma­t­ion in mice by caus­ing can­cer cells to age. The pro­cess curbed cell di­vi­sion.

The re­search­ers al­so found that a Skp2-blocking drug in­duced ag­ing in a lab­o­r­a­to­ry cul­ture of hu­man pros­tate can­cer cells.

Be­cause the new­found ag­ing path­way seems to op­er­ate only in can­cer, it raises hopes that it could prove a use­ful tar­get for an­ti-can­cer treat­ments, which might avoid harm­ing healthy cells, the re­search­ers ar­gued. Such a treat­ment might al­so have the ad­van­tage of op­er­at­ing in a wide ar­ray of dif­fer­ent can­cer types.

“The chal­lenge ahead is to test wheth­er these pre­clin­i­cal stud­ies in mice can be trans­lated in­to more ef­fec­tive can­cer ther­a­pies,” wrote Man­u­el Ser­rano is of the Span­ish Na­tional Can­cer Re­search Cen­tre in Ma­drid, in a com­men­tary ac­com­pa­nying the study in Na­ture.

A study has now found that the brains of psy­chopaths seem to be wired to keep seek­ing a re­ward at any cost. Sci­en­tists say the re­search clar­i­fies the role of the brain’s re­ward sys­tem in psy­chop­a­thy and opens a new ar­ea of study for un­der­stand­ing what drives these twisted minds.

The study from from Van­der­bilt Uni­vers­ity in Nash­ville, Tenn. is pub­lished in the March 14 is­sue of the re­search jour­nal Na­ture Neu­ro­sci­ence.


“Psy­chopaths are of­ten thought of as cold-blood­ed crim­i­nals who take what they want with­out think­ing about con­se­quences,” Josh­ua Buck­holtz, a grad­u­ate stu­dent in psy­chol­o­gy and lead au­thor of the new stu­dy, said. “We found that a hyper-reac­tive dopamine re­ward sys­tem may be the founda­t­ion for some of the most prob­lem­at­ic be­hav­iors as­so­ci­at­ed with psy­chop­a­thy, such as vi­o­lent crime, re­cid­i­vism and sub­stance abuse.”

Dopamine is the brain chem­i­cal most closely as­so­ci­at­ed with pleas­ure and ex­cite­ment.

Pre­vi­ous re­search on psy­chop­a­thy has fo­cused on what these peo­ple lack­—fear, em­pa­thy and in­ter­per­son­al skills. The new re­search, how­ev­er, ex­am­ines what they have in abun­dance—im­pul­siv­ity, height­ened at­trac­tion to re­wards and risk tak­ing, said Buck­holtz and his co-auth­ors. Im­por­tant­ly, the lat­ter traits are those most closely linked with the vi­o­lent and crim­i­nal as­pects of psy­chop­a­thy, re­search­ers said.

“There has been a long tra­di­tion of re­search on psy­chop­a­thy that has fo­cused on the lack of sen­si­ti­vity to pun­ish­ment and a lack of fear, but those traits are not par­tic­u­larly good pre­dic­tors of vi­o­lence or crim­i­nal be­hav­ior,” said Van­der­bilt psy­chol­o­gist Da­vid Zald, co-au­thor of the stu­dy.

“Our da­ta is sug­gest­ing that some­thing might be hap­pen­ing on the oth­er side of things. These in­di­vid­u­als ap­pear to have such a strong draw to re­ward—to the car­rot—that it over­whelms the sense of risk or con­cern about the stick.”

The re­search­ers used a brain im­ag­ing tech­nique called pos­i­tron emis­sion to­mog­ra­phy, or PET, to meas­ure dopamine re­lease, in con­cert with a probe of the brain’s re­ward sys­tem us­ing func­tion­al mag­net­ic im­ag­ing, or fMRI. “The really strik­ing thing is with these two very dif­fer­ent tech­niques we saw a very si­m­i­lar pat­tern—both were height­ened in in­di­vid­u­als with psy­cho­pathic traits,” Zald said.

Vol­un­teers for the study took a per­son­al­ity test to gauge their lev­el of psy­cho­pathic traits. These traits lie on a spec­trum: vi­o­lent crim­i­nals fall at its ex­treme end, but a nor­mally func­tion­ing per­son can al­so have psy­cho­pathic traits to some de­gree. These traits in­clude ma­ni­pu­la­tive­ness, ego­cen­tricity, ag­gres­sion and risk tak­ing.

The re­search­ers gave the vol­un­teers a dose of am­phet­a­mine, or speed, and then scanned their brains us­ing PET to view dopamine re­lease in re­sponse to the stim­u­lant. Sub­stance abuse has been shown in the past to be as­so­ci­at­ed with al­tera­t­ions in dopamine re­sponses. Psy­chop­a­thy is strongly as­so­ci­at­ed with sub­stance abuse.

“Our hy­poth­e­sis was that psy­cho­pathic traits are al­so linked to dys­func­tion in dopamine re­ward cir­cuit­ry,” Buck­holtz said. “Con­sis­tent with what we thought, we found peo­ple with high lev­els of psy­cho­pathic traits had al­most four times the amount of dopamine re­leased in re­sponse to am­phet­a­mine.”

The re­search sub­jects were lat­er told they would re­ceive some mon­ey for com­plet­ing a sim­ple task. Their brains were scanned with fMRI while they were per­form­ing the task. The re­search­ers found in those par­ti­ci­pants with more psy­cho­pathic traits the dopamine re­ward ar­ea of the brain, the nu­cle­us ac­cum­bens, was much more ac­tive while they were an­ti­cipat­ing the re­ward.

“It may be that be­cause of these ex­ag­ger­at­ed dopamine re­sponses, once they fo­cus on the chance to get a re­ward, psy­chopaths are un­able to al­ter their at­ten­tion un­til they get what they’re af­ter,” Buck­holtz said. Added Zald, “It’s not just that they don’t ap­pre­ci­ate the po­ten­tial threat, but that the an­ti­cipa­t­ion or mo­tiva­t­ion for re­ward over­whelms those con­cerns.”