How the elephant got its trunk

"In the High and Far-Off Times the Elephant, O
Best Beloved, had no trunk. He had only a
blackish, bulgy nose, as big as a boot, that he
could wriggle about from side to side..." Rudyard Kipling

The elephant got its trunk, the story goes,
because one small elephant child was so curious
as to what a hungry crocodile ate for dinner that
he got too close to it. The crocodile then bit and
pulled its bulgy nose and stretched it out.
From then on, the elephant child was able to
stuff large bundles of grass into its mouth with
ease.
The truth, of course, is likely to be different to
Rudyard Kipling's elephant child story.
And now researchers have sought to understand
exactly what that is; and establish why elephants
and giraffes have such long trunks and tongues.
The answer lies with the amount of food they
need to eat, a new study suggests. It's published
in the journal Acta Zoologica .
A team modelled how the tongues and trunks of
18 species of herbivore related to the amount of
food they took in while grazing.
The soft body parts – the lips tongues and
trunks - are the key to their survival
The elephant's trunk, they found, was vital for it
to eat enough food in relation to the size of its
mouth. So too was the giraffe's tongue. They
also helped the herbivores eat softer, more
nutritious plants such as leaves.
The team used a modelling process called
allometric scaling, a well-known biological "law"
which states that the size of an animal is in
proportion to how much it eats.
"We observed that they ate much more than you
would predict on the basis of their mouth volume
and skull dimensions," explains one of the
study's co-authors, Fred de Boer of Wageningen
University in the Netherlands.
"Basically the soft body parts - the lips tongues
and trunks - are the key to their survival,
otherwise they could not take in sufficient food,"
adds de Boer.
How much they can bite in one go (bite volume)
is therefore a direct result of these elongated soft
mouth parts. Smaller herbivores such as an
antelope do not need a large tongue to eat
enough food.
Not only are these structures key to the survival
of today's elephants and giraffes, the team further
proposes that they evolved as a direct adaptation
to the quality of edible plants in their
environment.
It may also explain why some larger herbivores
went extinct, says de Boer. During times of
sudden climate change, when food became
scarcer or less nutritious, other species may
have lacked suitable tongues or trunks to eat
enough food to survive.
However, as soft tissue is not preserved in the
fossil record, other researchers maintain there's
more to how tongues and trunks developed.
Palaeontologist William Sanders from
the University of Michigan, US, is not convinced
that this new analysis answers other aspects of
herbivore development which could have played
equally important roles in tongue and trunk
evolution.
The size of an animal's teeth, how it replaces
them in its mouth, and how an animal's guts
work, would all influence how it eats, and have
an impact on the evolution of trunks or tongues.
"Skulls, faces and mouths are formed of
interrelated anatomical complexes, and that
evolution of one part of these complexes will
almost always have an effect on the others," he
says.
About eight million years ago, elephant ancestors
relied heavily on grazing from the ground but
they had two sets of elongated tusks which
prevented them from eating with only their
mouths.
The elephant trunk, he says, evolved to such a
length to accommodate its large tusks.
So in one aspect of his story Kipling was not so
far off after all. The elephant child certainly could
eat more with its elongated trunk as can all
other elephants alive today.