A fossil cranium from Kenya tells the story of an extinct elephant species
William Sanders, The Conversation
November 22, 2021
Some 4.5 million years ago, during the early Pliocene epoch, Kenya’s Lake
Turkana looked very different than it does today. Grasslands and open
woodlands were spreading in cooler, drier climates. Competition for C4
grasses – the kind that grow in seasonal, tropical environments and were
well adapted for these new, cooler, drier conditions – was increasing
between mammals like horses, hippos, rhinos, antelopes, pigs and elephants.
Some of the oldest bipedal human ancestors, Australopithecus anamensis,
inhabited the same landscapes.
Flash forward to 2013. Apolo Longaye, a member of the Koobi Fora Research
Project, was prospecting the barren landscape for fossils at a site known
as Area 14, northeast of Lake Turkana near Ileret, Kenya. Longaye spotted a
single fossil elephant molar beginning to emerge from the ground. Project
leaders Meave Leakey and Louise Leakey decided to excavate the molar. They
discovered an entire cranium to which the molar belonged.
What followed was a remarkable collaborative effort by researchers in Kenya
and the US to recover, prepare, conserve, and study the cranium and its
The results of the study, which I led, reveal the cranium to be truly
extraordinary. It belonged to an adult male that was still growing at the
time of its death. It is much larger than the biggest crania of living
African elephants, correlating with a body size of about 3.7 metres from
the ground to the top of the shoulder and weight of about about 8000 kgs.
Its degree of preservation makes it the only nearly complete cranium of an
elephant to have been found in an interval from their origin at about 8
million years to about 3.5 million years ago.
The anatomy of the teeth in the cranium and its bones show that it belongs
to Loxodonta adaurora, an extinct cousin of the living African savanna and
forest elephants. It is also called the “dawn African elephant.”
This is an important finding because, by studying its teeth, we were able
to understand how this species physically shaped the landscape it occupied.
It also gives us new insight into an ancient species whose modern cousins
remain a part of our lives - for now, given that they are on the verge of
Recovery and Study
The first step in recovering the immense fossil elephant cranium – it
weighs more than 1800kgs – involved excavating it. It was then treated with
chemical preservative in the field, and secured inside a plaster-and-burlap
cradle on a metal frame. After this it was removed from the local sediments
and hoisted onto the back of a truck, aided by many of the project’s team
It was taken to the Turkana Basin Institute’s Ileret research facility for
permanent storage. There, it underwent initial preparation and further
chemical consolidation. This made the fossil accessible for study.
Meanwhile, geologists from the Universities of Utah and Rutgers studied the
rock sequence in Area 14. They wanted to establish the age of the fossil
and the geological context it was recovered from. They also wanted to
determine the conditions under which the elephant cranium had become
fossilised. Their investigations revealed that the rocks from which the
cranium was extracted were sandstones and conglomerates that had
accumulated in an ancient river. Bones have a better chance of becoming
fossils if they are quickly covered by sediments in lakes or rivers. There
work established that the cranium is as old as 4.5 million years.
Once this work was done, I undertook comparative research on the cranium.
This was designed to identify and properly describe it for publication. I
have studied the evolution and palaeoecology of African and Arabian
elephants and their closest relatives for almost 40 years, involving
fieldwork and investigations of fossil collections in museums from Cairo to
Apolo Longaye, who discovered the cranium, applies a chemical hardener to
it. Courtesy of Louise Leakey, Turkana Basin Institute and National
The cranium was measured in the Ileret facility using animal body calipers.
It is almost 1400 mm long and over 900 mm wide. It was also scanned in
Kenya to make 3D images, which allowed me to look at the cranium in its
entirety at the same time, remotely.
Built for the Task
We did more than just identify the elephant species and locate it in
geographical time. By studying its molars and cranium, the team was also
able to understand the animal’s chewing habits. It possessed abundant
adaptations for resisting the grit of eating close to the ground and for an
energy-efficient form of horizontal-shearing when chewing.
We found that the teeth of Loxodonta adaurora are higher-crowned and more
abundantly covered with protective cementum (in human teeth this hard
substance covers the roots; in elephants it extends up over the crown of
molars) than the molars of earlier elephants. The details of the new
cranium also show that it is unexpectedly modern in shape: tall and
compressed from front-to-back, an expedient arrangement to align the
chewing muscles perfectly to apply their force for grazing.
The advantages of having anatomy synchronised with feeding behaviour go a
long way to explaining why Loxodonta adaurora was the dominant elephant
known in eastern Africa at that time, particularly in the region around
what is now Lake Turkana: it was perfectly built for the landscape of the
Other species benefited from living in habitats opened up by elephant
feeding and movement activities. Elephants opened up closed woodlands and
forests to transform them into grasslands and open woodland, wooded
savannas and brushland.
In these conditions, an “ape” that adopted walking on two legs became
energy efficient to travel between patches of fruit trees and other
resources. Nascent bipedality in early hominins was perfect for these
conditions; without these conditions, bipedality would have conferred no
particular advantage and humans may not have continued to evolve into the
tool-making bipeds we are today.
It seems tragic that the current relatives of this Pliocene behemoth, and
with them the lineage that once created conditions for the early success of
our own evolution, now also face extinction – not because of natural
competition but due to avoidable human land encroachment, poaching, and the
environmental impacts of human-driven climate change.
William Sanders, Chief Vertebrate Preparator and Associate Research
Scientist in the Museum of Paleontology and Department of Anthropology,
University of Michigan