74 Science & technology The EconomistJuly 13th 2019
2 herteamhavenow done so, using tech-
niques unavailable to the original finders.
One fossil is a reasonably complete,
though fragmented, skull. Radioisotope
dating shows it is 170,000 years old. Com-
puter reconstruction reveals it to be an ex-
ample of Homo neanderthalensis, Neander-
thal man, a species widespread in Europe
until 40,000 years ago, when Homo sapiens
took over. The other fossil, the back half of
a cranium (pictured, attached to some
rock) turned out to be Homo sapiens. It is
210,000 years old, and thus the third-oldest
known example of modern humanity.
That is interesting. But what has excited
attention is that it is also the oldest Homo
sapiensspecimen found outside Africa—
the continent where, according to all the
available evidence, the species originated.
How Homo sapiensspread from Africa to
dominate the world is a story that once
looked simple, but is getting rapidly more
complex. Genetic data suggest most people
alive today who are not African or of recent
African descent can trace their ancestry to
one or a few “out of Africa” migrations that
began about 60,000 years ago into Asia,
and thence spread to Australia, Europe and
the Americas. More detailed analysis,
though, shows that on the way through
these places some of those ancestral hu-
mans interbred with other human species,
now extinct, including Neanderthals.
Fossils also show that Homo sapienswas
present in the Middle East well before
60,000 years ago. Not, however, as long ago
as the inhabitant of Apidima whose re-
mains Dr Harvati has now analysed. Why,
having reached Greece, Homo sapiensdid
not continue to spread into the rest of Eu-
rope and thus take it over 170,000 years ear-
lier than happened in reality is a mystery—
perhaps one on which future fossil discov-
eries will shed a little light. 7Mystery manCorrectionIn“Thefutureofflight”(Technology
Quarterly,June1st)wewrotethatWrightElectric,
anaircraftfirminCalifornia,isbackedbyLarry
Page.MrPageisindeedbackingsomeCalifornian
electric-aircraftcompanies,butWrightisnotamong
them.Sorry.I
n 1969 acruise ship called msLindblad Ex-
plorer, the first vessel purpose-built for
such a trip, and carrying 90 passengers, ar-
rived in Antarctic waters. Since then, Ant-
arctic tourism has increased dramatically.
Nowadays, well over 35,000 visitors a sea-
son make landfall in the austral summer.
Most of these landings take place on the
Antarctic peninsula and its adjacent is-
lands, with the intention of visiting colo-
nies of gentoo penguins.
That worries many conservationists,
who fear such quantities of people may be
disturbing the penguins, to the birds’ detri-
ment. However, a study just published in
Polar Biologyby Maureen Lynch of Stony
Brook University, in New York, brings good
news for penguins, tourists and tour-oper-
ators alike—for, as far as Dr Lynch can de-
termine, the tourists’ visits are not stress-
ing the birds at all.
The conventional way of deciding
whether visits by tourists are stressful to
the animals so visited is to recruit a bunch
of phdstudents to observe those animals
and make copious behavioural observa-
tions when tourists are and are not present,
in order that the two may be compared.This is arduous and expensive, for even
phdstudents, lowly as they are, need to be
housed and fed. An alternative is to sample
the animals’ blood and analyse it for stress
hormones such as corticosterone. The pro-
blem with this is that catching animals to
measure their hormone levels is, of itself,
stressful.
There is, however, a third way, which is
to look for stress hormones in animals’
droppings. Dr Lynch knew from previous
work by her collaborators at the University
of Houston that corticosterone and its me-
tabolites show up in penguin guano. More-
over, the data showing this hinted that cor-
ticosterone concentrations in guano went
up shortly after animals were approached
by human beings, and then returned to
normal later. With that in mind, she decid-
ed to compare guano from penguin colo-
nies visited by lots of tourists with those
farther off the beaten track.
She and her colleagues therefore visited
the Antarctic peninsula during the tourism
seasons of 2017-18 and 2018-19. Once there
they collected 108 guano samples from 19
gentoo penguin colonies and returned
them to the laboratory for analysis. A few of
the sites sampled (like Bryde Island and
Moot Point) are hard to get to and never see
tourists. Others see between 5,000 and
15,000 visitors a season. One (Neko Har-
bour) sees more than 20,000.
As the researchers expected, all the
samples contained corticosterone and its
associated metabolites. Contrary to their
expectations, however, there were no sig-
nificant differences between samples from
different sites, regardless of the number of
visitors those sites played host to. It seems,
then, either that penguins do not worry
about human visitors in the first place, or
that they quickly get used to them, which is
good news all round. What is more, Dr
Lynch’s method provides an easy way to
monitor the situation. If it does transpire
that, as tourist numbers grow, they cross a
threshold where they become oppressive
to the birds, it will be possible to advise
tour operators of the fact and ask them to
put their charges ashore to look at less-vis-
ited colonies. 7Contrary to the fears of some, penguins and people do mixConservation and tourismWhat? Me worry?
Ignore them. They’ll go away eventually...