Updated: Oct 19, 2019
Introduction: The African Elephant
The African elephant (Loxodonta africana) is the largest land mammal alive today. They have elongated appendages known as a trunk with two finger-like tips and, for the average mature bull, can grow to over three metres, weighing 5000 kilograms (Estes, 1991).
With these unique characteristics, one has to question how this creature came about. Have environment, natural phenomena and human presence played a part and what does the future hold for these huge animals? This report will discuss both the natural adaptation and evolution of the African elephant, showing us how it has become the animal we know today.
Taxonomy of elephant species
The taxonomic order in which elephants are members of is called Proboscidea. This order along with the family Elephantidae (mammals with tusks and trunks) hold all the extinct and living species of what we colloquially call elephants (Vaughan et al, 2011).
Elephants are divided into two species: Loxodonta and Elephas. Loxodonta africana is the mammal we know as the African Elephant which differs from its cousin (the Asian elephant, Elephas maximus) in many ways. They differ in anatomy from height and weight to dentition and behaviour (shown in table 1 below) (Fowler and Mikota, 2006).
Proboscideans first appeared in the mid-Eocene (about 45 million years ago) and the family Elephantidae in the late Miocene (about 6 million years ago). These were mostly large creatures, characterised primarily with their long trunks together with tusks (Estes, 2006). Table 2 below shows variation of species that evolved throughout these eras.
Loxodonta as a species evolved in Africa about four million years ago and this is where it remained. It has not changed much by the means of evolution in this time. Any adaptations of the African Elephant’s anatomy from fossil records around this time are subtle changes to its teeth and skeleton (Haynes, 1991).
Evolutionary Drives and Processes
The main evolutionary adaptations to the proboscidean anatomy occur in the animals teeth and other parts of the head. This has a lot to do with the distribution of the elephant ancestors and what part of the world they lived in (Haynes, 1991).
The distribution of proboscidean fossils is vast and are found nearly all over the world. This means ancient elephants each lived in a huge variety of habitats and environments. The two species alive today are the only successful representations of over 100 proboscidean species (see figure 3 below for examples). It was the ice age that wiped out the majority of large proboscideans and only those who had ventured to the subtropical landscapes of Africa and Asia continues to survive and evolve (Sukumar, 2003).
Figure 3; A range of proboscidean species which failed to survive the last ice age or survive evolutionarily. Taken from The living elephants (Sukumar, 2003).
There are a few studies which have been of interest in relation to modern adaptations in Loxodonta africana, in more recent history. There is genetic evidence suggesting that a sub-species of African elephant should in fact be classed as a separate species of Elephantidae. It showed that the 58% of genes that separate L.africana (African savannah elephants) and Elephus maximus actually differ from Loxodonta africana cyclosis (African forest elephants). Along with habitat and morphological differences, the forest elephant is now recognised as Loxodonta cyclosis, a different species (Roca et al, 2001).
We can see from Table 2 that the general size of the body, ears, trun
k and tusks increases the closer we get to the present era. It would appear that through the process of natural selection, the elephants with longer trunks get more food, are more likely to survive and therefore pass on these long-trunk genes to their offspring. This would be the same for longer tusks and fighting for the right to mate, bigger ears for losing heat quicker and bigger body size to avoid being killed by predators.
We have also found that natural phenomena such at the last ice age managed to wipe out Elephantidae species which allowed only the two we know of today to survive, but also that more recent history has given us adaptations which can separate a sub-species from Loxodonta vastly. This can give us an idea of why we have our modern elephants and why they have their unique characteristics.
Estes, Richard Despard, (1991). The behaviour guide to African mammals: including hoofed mammals, carnivores and primates. University of California Press, London, England.
Fowler, Murray E., and Mikota, Susan K., (2006). Biology, medicine and surgery of elephants. Blackwell Publishing Ltd, Oxford, United Kingdom.
Haynes, Gary, (1991). Mammoths, mastodonts and elephants: biology, behaviour, and the fossil record. Cambridge University Press, Cambridge, United Kingdom.
Roca, Alfred L., Georgiadis, Nicolas, Peacon-Slattery, Jill and O’Brien, Stephen J., (2001). Genetic evidence for Two Species of Elephant in Africa. Science magazine, 24 August 2001.
Sukumar, Raman, (2003). The Living Elephants: evolutionary ecology, behaviour and conservation. Oxford University Press, Oxford, England.
Vaughan, Terry A., Ryan, James M., and Czaplewski, Nicholas J., (2011). Mammaolgy. Fifth edition. Jones and Bartlett Publishers International, London, England.