Evolution of the Asian Elephant
Evolution of the Asian Elephant
he direct ancestors of Asian and African elephants
appeared about five million years ago in Africa. They evolved
from an animal, about the size of a large pig, named Moeritherium,
which lived near Fayyum, in Egypt, about 50 million years ago.
Moeritherium had no trunk, but its descendants evolved
into more than 30 species of trunked animals, all long extinct.
Some of them were much larger than today's elephants and they
lived in north and south America as well as in Africa and Asia.
The Asian elephant evolved from a form in Africa called Primelephas.
The family grew to more than 20 species, including mammoths, which
spread into Eurasia and the Americas. Mammoths are closely related
to living elephants, especially to the Asian elephant. One of
the best known is the woolly mammoth, which was about the same
height as the average Asian elephant - 3m at the shoulder. It
is widely depicted in Stone Age cave paintings dating back 20,000
years, and deepfrozen carcasses have been uncovered in Siberia,
complete with woolly hair and stomach contents.
The Asian elephant, Elephas maximus, is not only a separate
species from its African cousin Loxodonta africana, but
is placed in a different genus. It is smaller, although large
males still weigh up to 5,000kg and may reach more than 3.5m in
height. It is easily distinguished because its ears are much smaller
and its back slightly rounded or flat, unlike the concave saddleback
of the African species. Asian elephants have a single "finger"
on the upper tip of the trunk, while African elephants have a
second on the lower tip; and twin mounds on the forehead instead
of the African's single dome.
The elephant's trunk and tusks
The Asian elephant is surrounded by legend, with its spectacular
trunk the central theme. The trunk combines nose and upper lip
and enables an elephant to breathe, locate scents, drink, and
to seize and manipulate objects with extreme sensitivity. It is
used both for gentle caresses and admonitory slaps at its young.
It is not used as a weapon: a charging elephant will fold its
trunk back, using its forehead as a battering ram, its forefeet
to kick or trample, and its tusks to stab.
Unlike the African elephant, only male Asian elephants have tusks.
The females have small "tushes", which seldom protrude
beyond the lip. Some male Asian elephants do not grow tusks, but
these tuskless males, known in India as makhnas, are often
bigger than their tusked fellows.
Tusks are actually giant incisor teeth, which grow throughout
the elephant's life. The longest recorded pair, which are held
in Bangkok, are of 3m and 2.74m each. A shorter tusk from India,
and held in the British Museum, was heavier, weighing 146kg. The
relentless poaching for ivory in recent times has meant that tusks
approaching this size are no longer found.
Unlike humans and other animals, elephants have a "queue"
of six molars in each side of each jaw, which move forward as
each successive tooth wears out. With the loss of the sixth molar,
when an elephant reaches its sixties, it is doomed because it
can no longer feed.
The elephant's brain is larger than that of any other mammal at
birth (35% of the adult brain weight), accounting for its learning
ability, although smaller than the human brain in relation to
the elephant's size.
Smell is the most highly developed sense in elephants. They can
pick up surrounding scents on the breeze, and they constantly
feel and smell each other with their trunks. In this way males
pick up the pheremones which identify oestrus females ready to
mate. Eyesight is limited, but hearing is acute.
Although known for their loud trumpeting, it was discovered recently
that elephants also communicate with subsonic rumbles which can
travel up to five kilometres. This discovery solved the mystery
of the coordination observed in members of herds feeding at a
distance and out of sight of each other.
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