Head to Daniel Lieberman tracks the evolution of the human head. Toe by jonathan shaw

Beneath shelves of books on much of our sensory biology—are in the biology of bone, a collec- the head,” Lieberman explains. “It tion of skulls and running is the size of a soccer ball, and think shoes lies in a jumble on what it does”: seeing, hearing, tast- a countertop. The skulls ing, smelling, balancing, thinking, come in a range of sizes speaking, chewing, swallowing, and shapes, from the tiny breathing, and regulating body and sharp-toothed, with temperature. Lieberman’s book large orbits for the eyes, considers in detail how each of to the hefty and human- these functions works from a oid. The shoes are like- biomechanical perspective, wise varied, from brightly and then theorizes how each colored Nikes, to fluores- evolved, simultaneously with cent ASICS, to slipper-like the others, as part of an inte- Vibram FiveFingers™ with grated whole. separated toes—like a “The head presents an in- glove—intended to mimic teresting evolutionary para- barefoot running. These col- dox,” explains Lieberman, lections neatly bracket the chair of the new department research interests of Daniel Lie- of human evolutionary biol- berman, human evolutionary bi- ogy, “because on the one hand Human ologist: a head-to-toe interest in the (H. sapiens) it is so complicated that if anything human body, its morphology (the sci- goes wrong, the organism dies. On ence of an organism’s form, including the study of specific the other hand, it is where natural se- structural features), its development, and its evolution. lection can and has acted powerfully “I do seem to end up working on the two ends of the body, to make us what we are.” Everything and not so much in between,” he muses. “I never thought that is closely connected. For example, the would happen in my career. It’s bizarre.” roof of the orbits is the floor of the brain—if one chang- But the apparent dichotomy is bizarre only in the abstract, be- es, they both do. cause Lieberman’s interest in feet—and human endurance run- “How is it,” he asks, “that something so complicated and so ning—began with his interest in heads. The two subjects are vital can also be so evolvable?” One explanation involves modu- deeply linked. The theory that humans evolved to become endur- larity and integration. Not only do heads contain many modules ance runners so talented that a team of barefoot hunters on a hot (instructions for building an eye to see, for example, or an ear to African savanna could actually run a large antelope to ground listen), but each module is itself “intensely integrated in terms of is based in part on skeletal evidence from the head—a subject development, structure, and function….Changes to the size, the about which Lieberman has just published a weighty book, 15 shape, or the relative timing of development of each of the head’s years in the making. many modules offer a variety of opportunities for change.” Study- “Many of the things we value most—our big brains, speech, ing the head’s modules, Lieberman writes, may help us under-

Photographs by Jim Harrison, unless otherwise noted Harvard Magazine 25 A skull session with human evolutionary biologist Daniel Lieberman in the fossil room at the Peabody Museum. Millions of years of natural selection have shaped the human head. From left to right: a Neanderthal; Homo erectus; Homo habilis; Australopithe- cus africanus; Pan troglodytes (common chimpanzee); Homo sapiens (human). “Gonzo,” a Neanderthal skeleton, stands in the back.

pg 124 human vs chimp

26 January - February 2011 courtesy of Daniel lieberman “How isitthatsomethingsocomplicatedandvitalcanalsobeevolvable?” T complex structures.” ways in opment the evolution of and permit thatfunction affect devel with - tinkers how nature for “exploring opportunity an It the lineage.” diverged chimpanzee’s lineage from alsoprovides our since human head haschanged substantially whystand “the chanical stresses, so he decided to study the ofchewing effects stresses,chanical sohedecidedto study factor. As grow, bones shaperespondto their sizeand biome whether of soft food might diet be a contributing the modern wondered atimeforevolutionshort to explain—Lieberman have span of recorded in the history—too brief become smaller yearsago, nine About while why contemplating human faces isone. biomechanics Experimental work.) ashisown as well ofmany (Theniques. draws book onthe expertise scholars processed food. In Why food. processed short: doesthe head lookthe way itdoes? teeth the that and foreating brain, under aresuitable only tucked knows), (nobody chins to running), really faces that are small questions,ing aswhy such humans have bignoses(there isalink ofinterest he avers. sorts Nevertheless, takesupall Lieberman Head hough written To probe suchmysteries, uses avariety of tech Lieberman (Harvard University Press) “is not meant to notmeant beabestseller,” University (Harvard Press) “is so anyone read can it,The Evolution of the Human - - - involves much lessforce. than undertheheel, and the balloffoot, rather strike originatesunder of impactinaforefoot magnitude anddirection runners shows thatthe comparison ofbarefoot the ground. Bottom: A the runner’s foot strikes shoes aloneaffect how cal inbothcases; the legs andfeet isidenti- Middle: The positioningof when wearing shoes. but withthemidfoot forefoot whenunshod, the ground withthe running barefoot strikes athlete whogrew up Top: An eliteKenyan lobe is about 25 percent larger, 25percent lobe isabout relatively) to order ask in ques- human which (in for example, to that ofamodern the temporal ape’sskull, an within compare the volume orsizeofastructure easily and theirthree shapesin dimensions, lethimstudy bones other and of skulls scans research. Computerized mechanical the to bio complement modeling and comparative morphology B lifts to simulatehighheels. lifts with balsawood fitted onthethem sheepand put plasticbooties to seehowthat would affect develop,” how the joints sohisteam wearing high heels change the angles of theirWe joints. wanted sheep of “soundscrazy,” kind people admits, Lieberman “but shoeson employed sheep.of shoesonskeletal growth, Putting changed howmuchwe muscles.” derizing use chewing our invented,” hesays, we- “and want ten and howcooking to know was howhumansto managed cooking know to eatmeatbefore muscles “We using oftheir chewing electrodes. the activity want versus cookedgoat—a meat—and tough, measuring game-like faces jaws and leave forteeth. room too little ofmolarimpactions”—small heads our in terms nowin shift anything day long,”hesays. all “You seethe of effects can that now. many “Ithink peopletoday never chew have to actually they foodthan processed do access to high-energy had greater Andhumans, have out, softfood. hepoints neverhigh-quality very jaws chewing smaller between regularly and is there a link larger.suggestedthe pigs hardfoodgrow eating that The study other. made Thelower ofchewing and the jaws upper stresses of ofpigs,food to onegroup hardfoodto- an hefed soft mal In species. oneexperiment, various in - ani development ofthe skull andhard versus softfoodonthe growth that,” hesays, though analysis isnotyetcomplete. ofthe data “We beable the to effectfrom extrapolate of shoes wearing will ack inhisoffice “We that the sheepwere soondiscovered off muchbetter onthe effects experiment, biomechanical recent Another Recently humans raw by that feeding probing shift hehasbeen

in the in Peabody uses Museum, Lieberman puted axial tomography (CT) scans. puted axial rate ofthe shodsheepusing com- wereers able to the measure growth over the place.” shoes all would there bewould and comein themkicked off. In youthe morning wear them atnight,butthey always “Wetreadmill. to get them tried to ona feetrunning and on their front the day spent then wearing the shoes the The shoes.” then them and sheep hewould putthe then socksand on hislap in down the sheepwould lie developedence this method where sci- veterinary in adegree with mine the thought. “A postdocof wonderful smile plays across Lieberman’s face at wearing socks their with shoes.” A After afew months,After the research- H arvard M agazine 27 (La Ferrassie)(La Neanderthal -

Common chimpanzee (Pan troglodytes)

courtesy of Daniel lieberman runners are about 5 percent more economical than shod runners, shod moreeconomical than runners, 5percent are about runners economy. to running measure Lieberman barefoot out “It turns oxygen respirator formeasuring use allows afull-face ted with erectus fit by Homo amodelin testing ” Asecondtreadmill sapiens. apply to us, them and sowe estimate can the biteforceofHomo Newtonian and physics ofbiomechanics but the sameprinciples australopithecine orHomohow an habilis orHomo erectus behaved, because skeletonsexplains, have “We changed. can’t measure to development anatomy. and And ultimately, to evolution,” he jaw.chewing “We function and biomechanics tieforcesin can the way all on joints upto the He hips. a dothe samewith can to calculatethe forces Lieberman allows joints, the apparatus runner’s attachedmarkers fluorescent at a that track infrared space, preciselocationin and their own calculate that can cameras red video - infra high-speed from imagery with arecombined data theWhen treadmill bone.” of the growth how they affect the that applystrains to see that beamand “Wehe explains. the measure then can that asks, ‘How a beam?’” is a bonelike develop.and “We mighttestamodel man towork testmodelsofhowbones - Lieber allows the ground foot strikes the forceofimpact when arunner’s 28 Au.

J afarensis (Hadarreconstr F anuary -F H. MA=0. MA=1. n erectus(KNM-WT15000) F n 7 9 In anearby laboratory, that measures atreadmill ebruary 2011 F F g g tions about humantions about evolution. of CTscans stages of growth lethimposedevelopmen- stages ofgrowth atprogressively laterfetal human skulls uction) tal questions focusing on trade-offs in thetal questions focusing on trade-offs posed to another. expansion of one part of the skull asop- ofthe skull ofonepart expansion H. erectus(Zhoukoudianreconstr F H. n habilis(KNM-ER1813&OH13) MA=1. MA=1. F n ridges andnochins. faces, withbrow have large, protruding chins. Neanderthals retracted andinclude faces are smalland lemon-shaped. Human rounded, ratherthan human cranialvaultis Neanderthals. The of skulls ofhumansand differences between There are notable 2 8 F g F g uction)

- running,” Lieberman says. Lieberman yearsago, This wasrunning,” million two about ablethat the arebetter motionscaused torapidpitching sense by heads develop [the canals] semicircular ofbalance larger organs “We climates. arid the alsoseein fossilrecordwhen can human air, incoming air, exhaled to humidify the ability ordehumidify in severalin ways breathing, that adaptations may during increase that nasalcavities createturbulence inner short with combined Humans alsohavenosesrunning. external helpstheently head to remain stable during that appartached- atthe back ofthe skull, at the nape ofthe neck, at special ligament amongapes,of Utah. humans Alone have a the Universityhead Bramblefrom conjunction in Dennis with out “Wewhy.” to figure aretrying even you after account forthe weight ofthe shoe,”hereports. If you study the pharynx just from the just perspective from oflanguage the pharynx If you study ofit. has to do all yet that and onetube important incredibly ofthose things are All thermoregulation. breathing, and lowing, involved ofmuscles—“and of dozens somuch: in speech,swal- the elaborate inglydescribes interplay book complicated”—the “It’s he says, just a tube,” “but would walking orrunningthan balancing theheadwhile had amuch easiertime havespecimens would the three Homo that forcesof inertial show Biomechanical analyses to differences infunction. Differences ofform lead Lieberman’s his research on with the began in running interest Australopithecus. Early Modern Human Modern Early (Zhoudoudian 101)

nose is the most charismatic part. ofwhich the tobook the pharynx, heatstroke. from to ers chasepreyuntilitcollapsed lowed hunt early human endurance thatheads, al- may befeatures all morebalanced nose,along with and These changes the in ears, neck, when meat. eating humans began He devotes ofhisnew achapter wow! What a tube. It What is so a dizzy tube. - (La Ferrassie) Neanderthal about skullsandshoes. extras towatchvideos Visit harvardmag.com/ - -

courtesy of Daniel lieberman pens in conjunction with everything else.” else.” conjunction in everything pens with hap- the in everything head, preceded another; hard to say “It berman. that isvery onechange says problem,” Lie- that itisachicken-and-egg force). of facial reduction is challenge fun “The makes human jaws producing at moreefficient itchew (because tract); howwe and the vocalshortens itspeech (because thermoregulation; ing respiration and dur- of turbulence the amount pharynx; face affects the small the head. Having a connectedness in - the notionofinter way ofunpacking facestracted isanother hominins* other than ers of human evolutionary change: energy, change: ofhuman evolutionary ers driv to the speculateabout most important the Butin final head. pages, himself heallows in modules the relationships amongdifferent evolutionary developmental, and functional, to hisnewbook the in complex the discussion F conditions. the necessary all meets australopithecine head that ate ahypothetical cre possibilities—and the evolutionary with himto toyof speech.Suchmodelsallowed forthe development the possibilities strain systems the locatedin head orcon- to limit the life-supporting using modelsofall ment, - to engageina thought experi this strategy heemployed the book, to live.” writing When merely cal tractmustforaperson order doin the things other that avo all velopment, and de and respiration and of swallowing of speech, but also in terms the about youvocal notjust tract and terms dothatin by thinking “Butyouhe notes. have that to inference, around putprobabilities fairly impressive speech, but probably asours,” notasarticulate probably Neanderthals like had avocal that tract was capable of the evolution human example. relatives “Close ofspeechasan ofthe whole misspart story.” you will or thermoregulation affect howthejointsdevelop.” heels changetheanglesoftheirjoints.We wantedtoseehowthatwould Putting shoesonsheep“soundskindofcrazy, butpeoplewearinghigh placing orangutans in their own subfamily. their in own placing orangutans led to a reorganization of the Hominoid family by that orangutans ies ofchimpanzees, and gorillas, - molecularstud recent placefollowing in ofhominid, * Hominin, ahuman orhuman ancestor, isnowused or themost part, The fact that humans have smaller, morere the advantagesHe approach explains ofthisby holistic using Lieberman confines Lieberman the cranium. remains tucked under smaller humanface projecting, whilethe up tobecomemore faces grow outand and taller, butchimp cies, facesgrow wider growth. Inbothspe- in patternsoffacial highlight differences and humanskulls of adultchimpanzee Front andsideviews - - - -

courtesy of Daniel lieberman Human adul - graduate could go all day eating everything through dayastraw.” go could everything eating graduate all becauseeating ithasto chewraw, tough while food, - under an day half its spends Achimpanzee it. cooking itand processing we by foodand make iteven quality in higher high-quality really We’re food. animals eat low-quality animals that eat big-bodied energetically. creatures are “bizarre Forexample, mostbig-bodied is the most interesting of these, he says,Energy because humans habitat, speech. change, and open climate t Jonathan ’89ismanaging editor of Shaw this magazine. right?” speculating, some fun saysberman alaugh, with “You’ve got to have energy.” Pausing ofthoughts, histrain in Lie- new ways new and ways to get energy to use alot ofhuman evolutionI think was about ogy, of reproductive and ofcooking, shifts— technol- ofprojectile gathering, hunting and of ofbipedalism, origins “The he stresses. don’t even grow heads Our shift. energy an cessed foodsignals pro foreating fact thatteeth our aredesigned for the hasramifications body.whole ergy The sues: the fact that the- uses brain somuchen ofthe ofthe tis- costs thesee in head terms in thatman believes. issomething you “Ithink you energy,” about think tion unless - Lieber fat—are fat compared to primates. other body has10to 15percent cal hunter-gatherer - “Evenspecies. the thin amongst us—a typi Notsurprisingly,ance. we therefore, areafat - endur and forreproduction stored energy of ties, he continues, humans needreservoirs am—but amarathon.” my never dogcould run but pathetic atspeed:“My I than dogisfaster says. Most humans aregood at endurance, fiverun to 10 miles, let alone a marathon,” he willingly few animalsthat will arevery “There ning, aredistinctive another human feature: Now, we have can single year.” them every have three years. them every hunter-gatherers years.zee motherHuman six has babies every “A apeisasfecund. great no other - chimpan that constantly,” And out. points Lieberman The hasto brain expensive. have “incredibly supply atany moment— energy essential ofthe body’s 25percent ofthe bloodand cent Homo brain draws sapiens as much as 15 per The reproduction. and function brain in agant to locomotion,extrav regard in thrifty diture: “You simply can’t human evolu understand To capaci- power these extraordinary - run Energetic abilities, asendurance such - expen Humans arealsounusual energy in

properly because of cooking,” properly because ofcooking,”

H arvard M agazine 29 erectus Homo - - - -