The Modern day African Elephant (Loxodonta africana) and the Asian Elephant (Elephas Maximus) belong to the Proboscidean family: Elepahntae. There were 350 species in this order however, over time the majority of these has become extinct. The only two survivors are the African and Asian Elephants.
The Proboscideans were a species that inhabited every continent except Australia and Antarctica. They were able to survive and adapt to so many different environments and habitats.
This affected the species when radical changes came to their habitat and their large size proved a hindrance to their adaptive abilities. The evolution of Proboscidea is longer limb bones, Larger skulls and teeth and as they gave grown bigger so have their tusks.
Longer trunks have been an adaptation due to their heads being far away from the ground, this is so they don't have to bend over and eat leaving them less vulnerable to predators. Nature has favoured longer trunks.
The mammoth became extinct 5000 years ago, fossil records show that the hunting man was a factor as well as global warming
From biochemical and morphological evidence, manatees, dugongs and hyraxes are the closest living relatives to the modern day elephants