LIFE SCIENCES – Hob­bit mys­tery deep­ens

It’s clos­est rel­a­tive is a 1.75 mil­lion year old African. EL­IZ­A­BETH FINKEL re­ports.

Cosmos - - Digest -

The me­tre-tall Homo flo­re­sien­sis, pop­u­larly known as the hob­bit, just keeps up­end­ing the his­tory of hu­man evo­lu­tion. The lat­est chap­ter, pub­lished in the Jour­nal of Hu­man Evo­lu­tion in April, con­cludes that it’s clos­est rel­a­tive was Homo ha­bilis who lived 9000 kilo­me­tres away in Ethiopia. Not only has this left ar­chae­ol­o­gists scratch­ing their heads, it chal­lenges the text­book view that Homo erec­tus was the first an­cient hu­man species to leave Africa.

It was 2003 when Mike Mor­wood and col­leagues first re­ported the dis­cov­ery of the pa­pery bones of H. Flo­re­sien­sis along­side stone tools in the sed­i­ments of the vast Liang Bua cave in Flores. To Mor­wood the bones re­sem­bled those of Ethiopia’s fa­mous 3.2 mil­lion-year old Aus­tralo­p­ithecine, Lucy.

How could such a prim­i­tive ho­minin species have reached Flores? And how could they have en­dured till 18,000 years ago? That was the ini­tial date re­ported for the re­mains. Rather than ac­cept these mind-bog­gling propo­si­tions, some an­thro­pol­o­gists ar­gued the hob­bit was not an­cient but a dis­eased mod­ern hu­man, per­haps af­flicted by dwarfism.

The sug­ges­tion was that H. erec­tus ar­rived on the is­land and shrank – just like the Asian ele­phant that shrank to be­come Flores’ dwarf ste­godon.

That de­bate has largely gone away – aided by new dat­ing tech­niques in­di­cat­ing the hob­bits were a very en­dur­ing bunch: tool re­mains show they oc­cu­pied the cave from 190,000 to 50,000 years ago.

The new de­bate lies with the hob­bit’s an­ces­tors. Two re­cent stud­ies con­cluded that H. erec­tus was the clos­est rel­a­tive. That made sense: H. erec­tus skulls had, af­ter all, been found in nearby Java, though not on Flores it­self.

But a new anal­y­sis led by Deb­bie Ar­gue’s team at the Aus­tralian Na­tional Univer­sity pushes the pen­du­lum back closer to Lucy. While pre­vi­ous analy­ses em­ployed only skulls and teeth, the cur­rent study in­cluded 133 data points rang­ing across the skull, jaws, teeth, arms, legs and shoul­ders. The ver­dict? As far as de­scent from Homo erec­tus, “All the tests say it doesn’t fit,” Ar­gue says.

The in­side of the flo­re­sien­sis lower jaw was par­tic­u­larly telling. It showed pro­nounced re­in­forc­ing mounds known as the su­pe­rior and in­fe­rior tran­verse torus, never found in mod­ern hu­mans, and only in a very muted form in Homo erec­tus. Fur­ther­more the hob­bits had over­sized arms and feet like chimps – “body pro­por­tions much more like Homo ha­bilis or Aus­tralopethi­cus than Homo erec­tus,” ex­plains Ar­gue.

The lat­est anal­y­sis places the hob­bit as most likely a sis­ter species to H. ha­bilis, which lived in Africa about 1.75 mil­lion years ago.

How, then, did such a prim­i­tive ho­minin get to Flores from Africa – a jour­ney across wa­ter – more than 190,000 years ago? And if a rel­a­tive of ha­bilis did make it out of Africa, how come no other re­mains have been found along the way?

One way out of the quandary is to sug­gest that H. erec­tus ar­rived on the is­land and re­verted to a prim­i­tive form. Ar­gue finds this im­plau­si­ble: “Why would the jaw of Homo erec­tus evolve back to the prim­i­tive con­di­tion?”

Ul­ti­mately it’s a case of more ques­tions than an­swers.

Sci­en­tists have ob­served one of the most pow­er­ful astro­nom­i­cal events ever seen — the col­li­sion of two gi­ant black holes to form an even larger black hole.

It’s the third time since 2015 that such a col­li­sion has been ob­served by an in­stru­ment in the US called the Laser In­ter­fer­om­e­ter Grav­i­ta­tional-wave Ob­ser­va­tory (LIGO), which con­sists of a pair of de­tec­tors, one in Han­ford, Wash­ing­ton, and the other in Liv­ingston, Louisiana, each de­signed to mea­sure grav­i­ta­tional waves from dis­tant cos­mo­log­i­cal events.

Grav­i­ta­tional waves are rip­ples in the fabric of space, cre­ated by move­ments of mas­sive ob­jects.

“Nor­mally we don’t think of space as hav­ing any prop­er­ties at all, so it’s coun­ter­in­tu­itive,” says Michael Landry, di­rec­tor of LIGO’S Han­ford ob­ser­va­tory.

Nev­er­the­less, he says, Ein­stein’s the­ory of gen­eral rel­a­tiv­ity pre­dicts that space can ex­pand, con­tract or vi­brate, thereby dis­tort­ing the medium in which we all live.

These waves can be mea­sured, he adds, be­cause the dis­tor­tions they pro­duce look like changes in the length of any ob­ject they pass through.

Landry com­pares it to stretch­ing the can­vas of a paint­ing: “If I stretch the medium, the paint­ing gets dis­torted.”

In the lat­est case, LIGO saw the rapidly vi­brat­ing dis­tor­tions pro­duced as the two black holes spi­ralled to­ward each other be­fore merg­ing. The en­ergy thus re­leased in the form of grav­i­ta­tional waves was the equiv­a­lent of two Sun-sized stars be­ing de­ma­te­ri­alised in one-third of a sec­ond.

Once the col­li­sion was com­plete, the new black hole had a mass about 50 times that of the Sun.

It’s an im­por­tant find be­cause it sug­gests that black holes of this size may be fairly com­mon.

“Be­fore our dis­cov­er­ies we didn’t even know for sure that these black holes ex­isted,” says Laura Cado­nati of Ge­or­gia Tech Univer­sity. “We know now they do. They may have played an im­por­tant role in the early uni­verse.”

The new find­ing al­lowed re­searchers to cal­cu­late whether the col­lid­ing black holes were spin­ning in the same di­rec­tion as they cir­cled each other be­fore the col­li­sion.

“Imag­ine two tor­na­does ro­tat­ing each other,” says Laura Cado­nati of Ge­or­gia Tech Univer­sity. “They could be [in] the same as the or­bit, or op­posed, or at any an­gle in be­tween.”

Com­puter mod­el­ling showed that the sig­nals de­tected by LIGO con­tained the “grav­i­ta­tional fin­ger­prints” of black holes with spins that did not align with their or­bit.

Cado­nati says: “This favours the the­ory that these two black holes formed sep­a­rately then paired up, rather than be­ing formed from the col­lapse of two al­ready paired stars.”

The re­search was pub­lished in the jour­nal Phys­i­cal Re­view Let­ters.

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