BBC Focus - 09.2019

EXISTENTIAL FEAR OF THE MONTH...

I’M MORE BACTERIA THAN HUMAN

Therearemorebacterialcellsinyourbody

thanhumancells,buttheratioisn’tas

extremeasoncethought.A 2016studyat

theWeizmannInstituteofScienceinIsrael

foundthatourtotalcellcountis 56percent

bacteria(comparedwithearlierestimatesof

90 percent).Andbecausebacteriaaremuch

smaller,theirtotalmassis onlyabout

200g.Sobyweight,wearemorethan

99.7percenthuman.

Evenso,weshouldn’tunderestimatethe

contributionbacteriamaketoourbody,nor

feelthreatenedbyit.Mostofour‘human’

cellscontainstructurescalledmitochondria,

whichwerelyontoconvertglucoseinto

compounds we can use for energy. These

mitochondriaprobablybeganasfree-living

bacteriabeforetheyembarkedona

symbioticrelationshipwithus.Theonly

reasonthatwedon’tincludetheminour

tallyofbacteriais thattheyneverleavethe

confinesofhumancellmembranes,though

theyare,inmanyrespects,independent

organismswiththeirownDNA.

Likeallmulticellularanimals,wecan’t

easilypointtoindividualcomponentsand

say“Thisis partofme,andthisis not”.Your

bodyis likea city– it hasa collective

identitythatgoesbeyonditsindividual

inhabitants.Thepigeonsandsquirrelsthat

callLondonhomearejustasmucha part of

it as the humans who live there.LV

Thenumberofabnormal‘teeth’

removedfromthemouthofa seven-

year-oldboyinIndia.Theteeth,

whichwerefoundinsidea growthin

thelowerjaw,rangedinsizefrom

0.1mmto3mm,andeachhad

enamel, a crown and a small root.

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GETTY IMAGES X3, SCIENCE PHOTO LIBRARY ILLUSTRATION: DAN BRIGHT

JUNOSANDFORD(AGED5),HACKNEY

DO GIRAFFES

MAKE A NOISE?

Althoughnotthemosttalkativeofanimals,

giraesareknowntosnortorhisswhen

threatened,andfemalegiraesbellowto

theiryoung.Butwerecentlydiscoveredthat

theymakeothernoises,too.In2015,

researchersanalysedrecordingsofgiraes

fromzoosinBerlin,CopenhagenandVienna,

andfoundthattheymakelow-frequency

hummingnoisesatnight.It’sthoughtthat

theseotherworldlysoundsarea formof

‘contactcall’betweenindividualswhohave

beenseparatedfromtheirherd,helpingthem

tofindeachotherinthedark.Rather

charmingly,anothertheorysuggeststhatthe

hummingis actually giraes snoring or

sleep-talking!CC