Cold­est case in science solved

Sci­en­tists think they now know how Lucy, an early hu­man an­ces­tor who lived 3.2 mil­lion years ago, died.

The Star Malaysia - Star2 - - SCIENCE - By DEB­O­RAH NETBURN

IT’S the cold­est case in science, and it may have just been cracked.

Forty years af­ter re­searchers dis­cov­ered Lucy, an early hu­man an­ces­tor who lived 3.2 mil­lion years ago, sci­en­tists think they now know how she died.

Af­ter ex­am­in­ing high- res­o­lu­tion CT scans of bro­ken bones in Lucy’s right shoul­der, as well as the dam­age to other parts of her skele­ton, re­searchers at the Univer­sity of Texas at Austin pro­pose that the small ho­minid’s life ended shortly af­ter a cat­a­strophic fall from a great height – prob­a­bly from a tree.

“What we see is a pat­tern of frac­tures that are well doc­u­mented in cases of peo­ple who have suf­fered a se­vere fall,” said John Kap­pel­man, a UT pro­fes­sor of an­thro­pol­ogy and ge­o­log­i­cal sciences. “This wouldn’t hap­pen if you just fell over.”

In a pa­per pub­lished re­cently in Na­ture, Kap­pel­man and his col­leagues sug­gest that Lucy tum­bled out of a tree, landed hard on her feet and then pitched for­ward, ex­tend­ing her arms straight out in front of her in a des­per­ate at­tempt to break her fall.

The force of the im­pact of her hands hit­ting the ground is likely re­spon­si­ble for the de­bil­i­tat­ing com­pres­sion frac­ture in her shoul­der, the au­thors write.

But the fall also caused sev­eral bones in her body to break and prob­a­bly lead to se­vere or­gan dam­age. Death would have fol­lowed swiftly.

If their hy­poth­e­sis is cor­rect, Lucy was likely con­scious in the last few mo­ments be­fore she died.

“She did ex­actly what we would do,” Kap­pel­man said. “She was try­ing to save her life.”

Lucy was dis­cov­ered in 1974 by pa­le­oan­thro­pol­o­gist Don­ald Jo­han­son in the Hadar area of cen­tral Ethiopia. Jo­han­son and his col­leagues named the fos­sil af­ter the Bea­tles song Lucy in the Sky with Di­a­monds be­cause it was play­ing over and over again at their camp the night she was found.

Part of what made the Lucy find so im­por­tant was her un­usual mix of fea­tures. She had rel­a­tively short legs and long arms like a chim­panzee, but her wide pelvis in­di­cated that she walked up­right.

This com­bi­na­tion of traits sug­gests her species, Aus­tralo­p­ithe­cus afaren­sis, may have been a link be­tween modern hu­mans and our tree- liv­ing an­ces­tors.

Lucy was much smaller than modern hu­mans. Al­though she was prob­a­bly a full grown adult at the time of her death, she stood just 1.067 me­tres ( 3 feet 6 inches) tall, and weighed about 27.3kg ( 60 pounds) – about the size of a first- grader.

Her fos­silized re­mains have been stud­ied by dozens of sci­en­tists, but this is the first study to hy­poth­e­size how she met her end.

Kap­pel­man said that’s be­cause for the most part, an­cient bones do not re­veal how an an­i­mal died.

“De­spite what you see on shows like CSI, skele­tons only rarely pre­serve ev­i­dence of death,” he said. “If we didn’t see those arms stick­ing out, the ar­gu­ment we make might not be so pow­er­ful.”

Kap­pel­man’s re­search into Lucy’s demise be­gan in 2008, when the Ethiopian gov­ern­ment granted him 10 days to scan the pre­served parts of her skele­ton at the high- res­o­lu­tion CT lab at the Univer­sity of Texas.

Pre­vi­ous at­tempts to peer into the in­te­rior of Lucy’s bones in the late 1970s had failed be­cause CT scan­ners at that time were not pow­er­ful enough.

“Lucy is a fully min­er­al­ized fos­sil, so she’s like a rock, and the prob­lem with lower en­ergy CT is that they can’t see through rock,” Kap­pel­man said. “Up un­til 2008, we had no data at all on the in­ter­nal struc­ture of her bones. She was ra­dio­graph­i­cally opaque.”

It was while he was scan­ning her right humerus, the up­per arm bone, that Kap­pel­man re­alised the frac­tures on the end of the bone clos­est to the shoul­der were un­like any­thing he’d seen in other fos­sils.

Bone by bone, Kap­pel­man pieced to­gether the life and death of Lucy, the most fa­mous fos­sil of a hu­man an­ces­tor.

He con­cluded that she prob­a­bly died from in­juries suf­fered in a fall from a tall tree, sug­gest­ing that she for­aged or nested in trees.

An­cient fos­sils of­ten break apart due to ge­o­log­i­cal forces. For ex­am­ple, breaks could be caused by the tremen­dous pres­sure of rock that can build up on fos­sils over time. They can also frac­ture when shifts in the Earth’s crust tear them apart.

But Kap­pel­man thought the fis­sures in Lucy’s bones might have a dif­fer­ent ori­gin. Per­haps they were due to an in­jury in­stead.

To check his hunch, he called Dr Stephen Pearce, a friend of a friend and an or­thopaedic sur­geon at the Austin Bone and Joint Clinic. Pearce agreed to take a look at a cast of Lucy’s right humerus bone in his med­i­cal of­fice.

“It looked very dis­tinctly like a prox­i­mal frac­ture we see pretty rou­tinely as or­thopaedists, usu­ally be­cause of a fall off a lad­der or scaf­fold­ing, or a car crash,” Pearce said. “I’m not an an­thro­pol­o­gist, but it cer­tainly looked like the frac­ture pat­tern you would see if she fell out of a tree.”

Over time, Kap­pel­man showed his cast of the humerus to eight dif­fer­ent or­thopaedic sur­geons. All of them said it looked like a four- part prox­i­mal humerus frac­ture that oc­curs when a per­son puts out their hands to break a fall.

“It wasn’t like they were say­ing, ‘ It might be this or it could be some­thing else,’” Kap­pel­man said. “It was not even a ques­tion from their per­spec­tive.”

But how could the re­searchers know that the event that caused the bone frac­tures also caused her death?

Kap­pel­man and his co- au­thors ar­gue that the fall could not have oc­curred much be­fore Lucy died be­cause the bone breaks were clean and showed no sign of heal­ing.

They also say the in­jury could not have hap­pened long af­ter death be­cause tiny sliv­ers of bone that broke off in the im­pact re­mained in their post- in­jury po­si­tion rather than scat­ter­ing all over the ground. This could only hap­pen if the fi­brous tis­sue that forms a type of skin around the bone had not yet de­cayed, the au­thors said.

“Kap­pel­man’s point is that these sliv­ers of bone can only be ac­counted for if the fi­brous tis­sue was still there, hold­ing every­thing in place,” said Jack Stern, an anatomist and pro­fes­sor emer­i­tus at Stony Brook Univer­sity in New York who was not in­volved in the work. “That ar­gu­ment im­pressed me.”

In ad­di­tion, the au­thors de­scribe a se­ries of other dev­as­tat­ing frac­tures in Lucy’s left shoul­der, right an­kle, left knee, pelvis and first rib that are con­sis­tent with their great fall hy­poth­e­sis. But not ev­ery­one is buy­ing the ar­gu­ment. Jo­han­son, di­rec­tor of the In­sti­tute of Hu­man Ori­gins at Ari­zona State Univer­sity and the man who dis­cov­ered Lucy more than 40 years ago, said the pa­per does not pro­vide con­vinc­ing ev­i­dence for how Lucy died.

“Tens of thou­sands of fos­sils have been re­cov­ered by nu­mer­ous pa­le­on­tol­o­gists and they all show the same kind of bone break­age in­ter­preted by me and my team to be due to ge­o­log­i­cal forces,” he said. “Once these bones get in­terred in the wa­ter, sand­stone starts build­ing up on top of them and it’s a lot of pres­sure. These forces cause these kind of frac­tures.”

Ac­cord­ing to Jo­han­son, we will prob­a­bly never know how Lucy died.

Wil­liam Jungers, an an­thro­pol­o­gist at Stony Brook who re­viewed the pa­per for Na­ture, said he also had “se­vere doubts” about the pos­si­bil­ity of di­ag­nos­ing the cause of death in a fos­sil as old as Lucy.

How­ever, Kap­pel­man’s ar­gu­ment won him over.

“Vir­tu­ally ev­ery ma­jor reser­va­tion I had was an­tic­i­pated or ad­dressed head- on in the re­view process,” he said. “The de­tailed, com­pre­hen­sive anal­y­sis of her frac­ture pat­tern com­pared to the ex­ten­sive hu­man clin­i­cal lit­er­a­ture on skele­tal trauma re­sult­ing from a rapid ‘ ver­ti­cal de­cel­er­a­tion event’ is es­pe­cially com­pelling to me.”

Al­though “pa­leo- foren­sics” doesn’t al­low for repli­ca­tion ex­per­i­ments, John Flea­gle, an evo­lu­tion­ary bi­ol­o­gist at Stony Brook who was not in­volved in the work, said there may be ways to test Kap­pel­man’s hy­poth­e­sis.

“If the bones of an­telopes, warthogs and lions show sim­i­lar bone break­age, it prob­a­bly wouldn’t be due to a fall from a great height,” he said. “I look for­ward to see­ing such a study.” Kap­pel­man said he’s work­ing on it. “My co- au­thor Dr Todd and I are cur­rently work­ing up the fos­sils from Trinil in Java, the site where Homo erec­tus was first dis­cov­ered in the 1890s. There are many thou­sands upon thou­sands of fos­sil mam­mals ( in­clud­ing Homo erec­tus) at this site,” he said. “Spoiler alert: Not a sin­gle one of these thou­sands of fos­sils show any frac­tures sim­i­lar to the com­pres­sive frac­tures pre­served in Lucy’s skele­ton.”

In the mean­time, peo­ple with ac­cess to a 3- D printer can eval­u­ate the find­ings pre­sented in the pa­per for them­selves.

The Ethiopian Na­tional Mu­seum has made a set of 3- D files of Lucy’s shoul­der and knee avail­able on­line at eLucy. org that will let users repli­cate Lucy’s bones in the com­fort of their homes and class­rooms. – Los An­ge­les Times/ Tri­bune News Ser­vice

It looked very dis­tinctly like a prox­i­mal frac­ture we see pretty rou­tinely as or­thopaedists, usu­ally

ecause of a fall o a lad­der or sca oldin , or a car crash. I’m not an an­thro­polo ist, ut it cer­tainly looked like the frac­ture pat­tern you would see if she fell out of a tree. dr Stephen pearce, or­thopaedic sur­geon

— tnS

Univer­sity of texas pro­fes­sor John Kap­pel­man holds 3- d- printed copies of pieces of Lucy’s skele­ton. Lucy suf­fered com­pres­sive frac­tures in her right humerus when she died 3.2 mil­lion years ago.

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