The Economist - USA (2022-01-22)

72 Science & technology The Economist January 22nd 2022

onesduringyouth.Repairsneed notbe

perfect—just successful enough to keep

theshowontheroad.Anti­cancermecha­

nismsneedtobetip­topforthefirstde­

cadesoflife,butcangetslackerwithtime.

Ascantheimmunesystem.Thoughthey

will,nodoubt,buildoutwardfromtheir

starting point, Altos’s researchers will

surelyhavetoincorporatemoreaspectsof

molecularbiologythanthosetheyarebe­

ginningwith,inordertocoverthesebases.

The counterargument, put by Dr

Klausnerandhiscolleagues,isthatreset­

tingtheclockisa naturalprocess.Ithap­

penseverygeneration.The reproductive

cellswhichcreatethesenewgenerations

geta freshstarteachtime.Theyreallydo

returntofactorysettings.Andiftheclock

canberesetforthosecells,whynotothers?

WhetherDrMilner,MrNelsenandtheoth­

erswhohavebackedthefirmseea return

ontheirinvestmentwilldepend,aboveall,

ontheanswertothatquestion.Butitwill

befascinatingtoseeit asked.n

Childpsychology

Drools of

attraction

T

hecomplexitiesofhumanrelations

are difficult enough for adults to navi­

gate—and  they  have  at  least  some  idea  of

the rules. Children have yet to learn those

rules. Infants are, nonetheless, able quick­

ly  to  identify  close  relationships  between

other people, and thus to build up a map of

the social world around them. How they do

this has perplexed sociologists, anthropol­

ogists  and  developmental  psychologists

for  decades.  In  a  paper  just  published  in

Science,  Ashley  Thomas  of  the  Massachu­

setts  Institute  of  Technology  proposes  a

partial answer: slobber.

To avoid the sexual connotations of the

word “intimacy”, Dr Thomas and her team

refer to the “thickness” of interactions be­

tween  infants  and  adults—borrowing  the

term from Avishai Margalit, a philosopher.

Thick relationships involve strong attach­

ments,  obligations  and  mutual  respon­

siveness. One set of cues for thick relation­

ships relates to things that involve sharing

saliva:  kissing,  for  example,  or  the  com­

mon use of an eating or drinking utensil. 

To test whether children interpret sali­

va­sharing  as  indicating  a  thick  relation­

ship, the researchers recruited two groups

of several dozen youngsters. One was a set

of  babies  aged  between  eight  and  ten

months. The other was a group of toddlers

aged  between  16  and  18  months.  To  avoid

the hazards of covid­19, all tests were con­

ducted over a video link. 

Each child was shown a clip of an adult

interacting  with  a  puppet,  followed  by  a

clip  of  that  puppet  in  distress  while  the

same adult, and also a stranger, looked on.

When  the  interaction  in  the  first  clip  ap­

peared  to  involve  the  sharing  of  saliva—

with puppet and adult portrayed as taking

consecutive  bites  from  an  orange—both

sets of children looked mainly at that same

adult in the second clip, and not the strang­

er, a reaction interpreted as a belief that the

adult  in  question  would  offer  comfort  to

the  puppet.  When  the  interaction  in  the

first  clip  was  friendly  but  less  thick,  such

as  passing  a  ball  back  and  forth,  the  chil­

dren had equal expectations of both adults

when  shown  the  second  clip.  Saliva  shar­

ing seems, then, indicative of closeness.

That conclusion was reinforced by sub­

sequently replacing the puppet with a dif­

ferent  one  and  repeating  the  second  test.

In this case the children showed no consis­

tent expectation about which adult would

intervene to relieve the puppet’s distress. It

thus seems to have been the act of sharing

an orange with a specific puppet that trig­

gered  an  expectation  of  future  behaviour,

rather than any inherent characteristics of

the adults involved.

Conducting  her  experiment  by  video

enabled  Dr  Thomas  to  cast  her  search  for

trial  participants  beyond  Massachusetts.

She  nevertheless  decided,  in  this  first  in­

stance,  to  confine  things  to  the  United

States.  Future  runs,  she  hopes,  will  reach

beyond that country’s borders. 

The  ethnographic  literature  suggests

saliva­sharing  is  a  widespread  phenome­

non. It also makes sense as a signal of inti­

macy, for its disease­spreading potential is

obvious and engaging in it therefore indi­

cates a high degree of trust between partic­

ipants. But seeing how practice variesfrom

place to place (if, indeed, it does),might il­

luminate some intriguing details.n

Babies learn about people by looking

at who shares saliva

Thick as thieves

Tropicaldiseases

Resistance

is useless

A

n arms race between  pharmacolo­

gists  and  malaria  parasites  has  been

going on since the mid­19th century, when

widespread use of quinine began. Few bet­

ter  illustrations  of  natural  selection  exist

than the repeated emergence of resistance

to such drugs. Even artemisinin, the most

recent addition to the arsenal, has already

provoked an evolutionary pushback. 

At  the  moment,  working  out  which

drugs, if any, a particular case of malaria is

resistant  to  means  sending  a  sample  to  a

laboratory  for  a  pcrtest.  But  malaria  is

most  often  a  problem  in  poor  countries,

where such laboratories are scarce, and so

is  money  to  pay  for  tests  and  to  maintain

the  machines  needed  to  conduct  them.  A

better  way  for  doctors  and  paramedics  in

the  field  to  be  able  to  tell,  for  a  particular

patient, which drugs the infection is resis­

tant  to  would  thus  be  welcome.  And  that

may  soon  be  possible,  thanks  to  work  by

Ron Dzikowski and Eylon Yavin of the He­

brew  University  in  Jerusalem.  As  they

write  in  acsSensors,  they  have  come  up

with  a  trick  which  they  think  could  be

turned into a cheap and deployable detec­

tor for drug resistance.

The term “malaria” covers several simi­

lar  illnesses  caused  by  single­celled  para­

sites of the genus Plasmodium. The deadli­

est,  Plasmodium falciparum,  kills  around

600,000  people  a  year,  80%  of  them  chil­

dren under five. Dr Dzikowski and Dr Yavin

therefore focused their attention on this. 

They knew from research by others that

many of the drug­resistant traits in P. falci-

A field test for drug-resistant malarial

parasites will help save lives

Little bleeder