BBC Focus - 09.2019

Q&A

Expertsbelievethattheancestorsofmodernhumansbeganwalkinguprightatleast3.6

millionyearsago.Yetthereasonwemoveourarmsoutofsyncwithourlegshasonlyrecently

beensolved.Foryears,theanswerwasthoughttobesimplybalance.Researchpublishedin

2010 bya teamledbyDrSjoerdBruijnattheFreeUniversity,Netherlandsconfirmedthis– but

witha twist.Swingingourarmsdoesn’tmakeusmuchmorestablewhenwalkingnormally

• butit doeshelprestoreourbalanceif wesuddenlyloseourfootingwhilewalkingover
  unevenground.Earlierthisyear,Bruijnandcolleaguesalsofoundanotherbenefit:swinging
  ourarmswhilewalkingis moreenergyeicientthankeepingthemstill.Whileit takesenergy
  tomoveourarms,thisis morethancompensated for by the reduced energy needed by the
  rest of the body to propel itself forward.RM

THEODOREBARKAS,ATHENS

WHY DO WE SWING OUR ARMS WHEN WE WALK?

JANETLANE-

CLAYPON

HIDDEN

FIGES

Thescienceofepidemiologyhassaved
thelivesofmillionsbyhelpingtoreveal
thecausesofgoodandbadhealth.Using
so-calledcohortstudies,researchers
havemadesomecrucialdiscoveries,
showingthedeadlylinkbetween
smokingandcancer,forexample,andthe
benefitsofexerciseformentalhealth.Yet
thescientistwhopioneeredthistypeof
studywasforcedtoabandonresearch
anddiedinobscurity– chie￿y because
shewasa woman.
BorninLincolnshirein1877,Janet
Lane-Clayponwasa brilliantmedical
studentwhobecamefascinatedby
epidemiology.In1912,shepublisheda
pioneeringstudyoftwogroups–
‘cohorts’– ofbabies,fedbreastmilkand
cow’smilkrespectively.Using
sophisticatedtechniques,shenotonly
discoveredthelinkbetween
breastfeedingandbe￿ergrowth,butalso
ruledoutotherpotentialexplanations,
suchasfamilyincome.
Lane-Clayponthendeveloped
so-calledcase-controlstudies,wherea
groupofpeoplewitha diseaseare
comparedtoa broadlysimilargroupfree
ofthedisease.Thisallowedherto
identifyriskfactorsforbreastcancerthat
arestillrecognisedasimportanttoday.
Butin 1929 shemarrieda civilservantand
wasforcedtoquitundero￿icial
regulations.Whileotherstookupher
brilliantwork,Lane-Clayponherself
remainsunknowneven to those using her
techniques.RM

JESSROCHEFORT

WHAT WOULD HAPPEN IFALL THE SALT IN

THEOCEANS SUDDENLY DISAPPEARED?

A litreofseawatercontainsaround35gofdissolvedsalt,sodesalinatingtheentireoceanwould

involveremoving 45 millionbilliontonnesofsalt.Thesuddenreductioninweightpressingon

theseabedwouldprobablytriggerearthquakesandvolcanoesaroundtheglobe.Because

freshwateris lessdense,theArcticicecapwouldsinkanextra10cmintothewater,creatingthe

largesttidalwavetheplanethaseverseenalongnorthernEurope,RussiaandCanada.A few

hourslater,virtuallyallmarinelifewoulddieastheircellsswelledandrupturedduetoosmosis

(watermoleculesmovetowardsareasofhighersaltconcentration).Theywouldsinktothe

oceanoor,buttheirbodieswouldn’tdecompose,becauseallmarinebacteriawouldbedead

too.MarinealgaeareresponsibleforatleasthalfofEarth’soxygenproduction,sotherewould

bemassextinctionsonlandaswell.Eventually,theoceanswouldresalinatebecauseminerals

arecontinuallydissolvedfrom the land by rivers and carried to the sea, but this would take tens

of thousands of years.LV