58 THE SCIENTIST | the-scientist.com
F
or the past 150 years, scientists and
laypeople alike have accepted a
“savanna” scenario of human evolution.
The theory, primarily based on fossil evidence,
suggests that because our ancestral ape family
members were living in the trees of East
African forests, and because we humans live
on terra firma, our primate ancestors simply
came down from the trees onto the grass-
lands and stood upright to see farther over
the vegetation, increasing their efficiency
as hunter-gatherers. In the late 19th cen-
tury, anthropologists only had a few Nean-
derthal fossils to study, and science had very
little knowledge of genetics and evolutionary
changes. So this savanna theory of human
evolution became ingrained in anthropologi-
cal dogma and has remained the established
explanation of early hominin evolution fol-
lowing the genetic split from our primate
cousins 6 million to 7 million years ago.
But in 1960, a different twist on human
evolution emerged. That year, marine biolo-
gist Sir Alister Hardy wrote an article in New
Scientist suggesting a possible aquatic phase
in our evolution, noting Homo sapiens’s
differences from other primates and simi-
larities to other aquatic and semi-aquatic
mammals. In 1967, zoologist Desmond
Morris published The Naked Ape, which
explored different theories about why mod-
ern humans lost their fur. Morris men-
tioned Hardy’s “aquatic ape” hypothesis
as an “ingenious” theory that sufficiently
explained “why we are so nimble in the
water today and why our closest living rela-
tives, the chimpanzees, are so helpless and
quickly drown.”
Morris concluded, however, that “despite
its most appealing indirect evidence, the
aquatic theory lacks solid support.” Even if
eventually the aquatic ape hypothesis turns
out to be true, he continued, it need not com-
pletely rewrite the story of human evolution,but rather add to our species’ evolutionary
arc a “salutary christening ceremony.”
In 1992, I published a paper describing a
curious ear condition colloquially known as
“surfer’s ear,” which I and other ear, nose, and
throat doctors frequently see in clinics. Exostoses
are small bones that grow in the outer ear
canal, but only in humans who swim and dive
on a regular, almost daily basis. In modern
humans, there is undisputed evidence of aural
exostoses in people who swim and dive, with
the size and extent being directly dependent
on the frequency and length of exposure to
water, as well as its temperature.
I predicted that if these exostoses were
found in early hominin skulls, it would provide
vital fossil evidence for frequent swimming
and diving by our ancestors. Researchers
have now found these features in 1 million–
to 2 million–year-old hominin skulls. In a
recent study on nearly two dozen Neander-
thal skulls, about 47 percent had exostoses.
There are many other references to contem-
porary, historical, and archaeological coastal
and river communities with a significantly
increased incidence of aural exostoses. In my
latest book, The Waterside Ape, I propose
that the presence of exostoses in the skulls of
ancient human ancestors is a prime support
for an aquatic phase of our evolution, which
may explain our unique human phenotype.
OtherHomo sapiens–specific features
that may be tied to a semi-aquatic stage of
human evolution include erect posture, loss
of body hair, deposition of subcutaneous fat,
a completely different heat-regulation system
from other primates, and kidneys that func-
tion much like those of aquatic mammals.
This combination of characteristics, which
do not exist in any other terrestrial mammal,
would have gradually arisen over several mil-
lion years. The finding of the bipedal hominin
named “Lucy,” dating to 3.5 million years
ago, suggested that walking on two legs wasthe initial major evolutionary adaptation
to a semi-aquatic habitat. By the time the
Neanderthals appeared some 400,000 to
300,000 years ago, their semi-aquatic life-
style—swimming, diving, and perhaps hunt-
ing for food on land and in the water—may
have been firmly part of day-to-day life.
In my opinion, the accumulated fossil,
anatomical, and physiological evidence
about early hominin evolution points to
our human ancestors learning to survive
as semi-aquatic creatures in a changing
East African environment. After tran-
sitioning to bipedalism, ancient homi-
nins had both forelimbs free from aiding
in walking, which may have allowed for
increasing manual dexterity and skills.
Perhaps a marine diet with lipoproteins
that are essential for brain development
fueled the unique intellectual advances
and ecological dominance ofHomo sapiens.gPeter Rhys-Evans works in private practice
as an otolaryngologist in London at sev-
eral hospitals including the Harley Street
Clinic. He is the founder and chairman of
Oracle Cancer Trust, the largest head and
neck cancer charity in the UK. Read an
excerpt from The Waterside Ape at the-sci-
entist.com. Follow Rhys-Evans on Twitter
@TheWatersideApe.CRC Press, July 2019READING FRAMESA new book revives a controversial hypothesis that proponents
say may shake up scientists’ view of human evolution.BY PETER RHYS-EVANSHumanity’s Watery Beginnings