The Week 22Feb2020

NEWS 19

Fossilsunearthedinadesertregion of

Venezuelahave shednew lighton one

of the biggest-everturtles: the car-sized

Stupendemys geographicus.First described

by palaeo ntologists in the1970s,the turtle

livedbetween12 mill ion and sevenmillion

years agoinwhat, at thetime, was avast

swamplandpopulatedbymanyother

oversizedanimals,including11-metre-long

crocodiles and700kg rats. With itsthree

metre-longshell and estimatedbody mass

of 1,145kg,Stupendemysis th ought to have

been 100 time sheavierthan itsclosest li ving

descendent, the Amazon riverturtle.

The newlydisc overed fossils reveal that

Stupendemysmales hadfront-facinghorns onitsshell –anadaptatio nnever

previously seen in side-necked turtles(so namedbecauseinstea dofretractingtheir

necks, they tuck them sidewaysbeneaththe fron toftheir shells).Itisthought they

used thesebothtofightother males and to defend themselvesagainstpredators.

“Bite marksand punctured bones indic ateinter actionswith large caimans thatalso

inhabitedthenorthernNeotropics,”theresearcherswrote in ScienceAdva nces.

Health &Science

22 February 2020 THE WEEK

Girlsarehittingpubertyyounger
Aroundtheworld,girlsarestarting
pubertyaboutayearearlierthantheydid
fourdecadesago,anewstudyhasfound.
Theonsetofmenstruation(menarche)has
traditionallybeenseenasthemarkerfor
femalepuberty,buttheauthorsofthe
latestresearchsaythisisproblematic:
firstlybecausemenstruationcanbeginlater
thanothersignsofpuberty,andsecondly
becausepeoplemaynotrememberexactly
howoldtheywerewhentheyhadtheir
firstperiod.Sofortheiranalysis,the
Danishteamtookastheirmarkerthe
developmentofglandularbreasttissue
(thelarche).Havingexamineddatafrom
30 studiesforwhichgirlshadtheirbreast
tissueexpertlyassessed,theyworkedout
thatsince 1977 ,girlshave,onaverage,
beenreachingthismilestoneaboutthree
monthsearlierwitheverypassingdecade.
(Therewereregionalvariations,however,
withgirlsinAfricareachingpubertylater
thanthose inEuropeand theUS.) The
studydidn’t setoutto explainwhypuberty
iscreepingforward,buttheauthors
suggestthat sinceahigher body mass
indexhasbeenlinkedtotheearlier
developmentof glandularbreasttissue,
the“ongoing globalobesity epidemic”
couldbeapartialexplanationforthe
observedchange inpubertalage.

The wonders ofatable cloth
Ifyouwanttoimpressyourfriends with
your culinaryskills,dustoffyour table
cloth.InaGermanstudy,dinersgave
highermarksto abowloftomatosoup
whenit wasservedon asimplewhite
and greycheckedcloth;theyalsosat at
thetableforlonger,and polishedoffmore
ofit.Dimming thelighting,however,had
littleimpact:itjustmadethesoup taste
saltier.Thestudyisthelatest inthe field

of“gastrophysics”–assessinghow

perceptions oftasteare affectedbythe

environment.In2015,forinstance,

OxfordUniversityresearchersfound that

people enjoytheirfoodmorewhenthey

eatitwith heavycutlery. People have also

beenfound torate cheapwine more highly

when they aretoldthatitis expensive.

Anew way to diagnose cancer?

Scientistshave discoveredthatthegenetic

mutationsthatgiverisetocancercan

occurdecadesbefore symptomsappear,

raisingthepossibility ofdevelopingan

entirelynew way ofdiagnosingthe disease,

muchearlier. Forthe study,an

internationalteam sequencedthe genomes

of nearly 2 ,700tumours.Thisenabled

themto modelthetypical “lifehistory”of

each cancer,and tospotwhen thecrucial

“driver” mutations startedto occur.They

foundthattherewasconsiderable

variationbetween differentforms:with

ovariancancer,the drivermutationsbegan

up to35 yearsbeforethediseasewas

diagnosed(suggestingtell-talesignscould

havebeenthereasearlyaschildhood);

withkidney,bladderandskincancers,

the mutationsoccurredalmost20years

beforediagnosis;butwithliver and

cervicalcancer,it waslessthanfive years.

“Unlockingthesepatternsmeansit should

now bepossibletodevelop newdiagnostic

tests that pick upsignsofcancermuch

earlier,”saidco-authorDrPeterVanLoo,

oftheFrancisCrickInstitute inLondon.

West Africa’s “ghost” people

UCLA scientistshave found evidenceofa

mys terious“ghost population”ofancient

humans,wholived inAfricahalf amillion

years ago.Theevidencehasnotcomein

theformofafossil–but inpiecesof their

DNA foundin people fromWest Africa

today. “Wedon’t haveaclear identity for

thisarchaicgroup,”saidcomputational

biologist Prof SriramSankararaman.

“That’swhy weuse theterm‘ghost’.”This

populationprobablysplitfromthelineage

thatledtoHomosapiens,Denisovansand

Neanderthalsasmuch as1.2million years

ago,he said.TheancestorsofDenisova ns

movedeast, andthose ofNeanderthals

migratedwest–butit seemsthemystery

populationstayed inAfrica,whereHomo

sapiensevolved.The “introgression”

betweentheghosts and the ancestorsof

modernWest Africanscould have occurred

within thepast 125,000 years,aroundthe

sametime asDenisovansandNeanderthals

werematingwithhumansinAsia and

Europerespectively. Accordingtothe

study,modern WestAfricansderive

between 2 %and 1 9%oftheirgenetic

ancestryfromthisarchaic population, just

as allnon-Africanshaveinherited DNA

fromNeanderthalsand/orDenisovans.

Instantly tastier

Antarctica has logged its highest ever

recorded temperature–areading of

20 °Ctaken on Seymour Island, off the

Antarctic Peninsula. The reading was a

single one, not part ofalong-term data

set; but it was made justafew days after

arecord 18.3°Cwas logged on the tip

of the Antarctic Peninsula, at the

Esperanza Base. The “finger” that sticks

out from the northwest of the continent,

the peninsula is one of the fastest-

warming places on Earth, having heated

by almost 3°Cover the past 50 years.

Temperatures there do fluctuate, owing

to complex weather patterns in the area;

however, the trend is upwards–which

is alarming, given the possible impact

on Antarctica’s ice sheets. “We tend to

think of Antarctica as remote and

beautiful, home to iconic wildlife,” John

King, of the British Antarctic Survey, told

The Times. But “90% of the ice locked

up in the world is in these ice sheets”.

AbalmydayinAntarctica

Stupendemysgeographicus

What the scientists are saying...

The turtle that was as bigasacar