The rapid evolution of the family Elephantidae throughout time has been extensively researched in the past decades and has resulted in many new discoveries and lineages between the genuses of Elephantidae. Throughout evolution, a majority of the species of Elephantidae have become extinct, leaving only Loxodonta africana, Loxodonta cyclotis, and Elephas maximus. The number of these species, however, has dwindled significantly in the past years due to the high number of deaths of elephants due to poaching. The continuation of poaching has a possibility of a new evolutionary event within the elephants, elephants without tusks.
Ancestors of the extant Loxodonta africana and Elephas maximus
The family of Elephantidae shows a high rate of evolution, early stages of which were confined to Africa, while later stages occurred in Eurasia (Kalmykov & Mashchenko, 2006). Numerous studies have been conducted to understand the phylogeny of Elephantidae, and many of the researches have concluded different answers. Maglio, Beden, and Todd each concluded their research with phylogenetic trees that contrasted with each other.
According to Maglio (1972), the lineages of Loxodonta, Elephas, and Mammuthus all evolved from the ancestor Primelephas gomphotheroides. Loxodonta first evolved from the Primelephas in the Pliocene time period, leaving an Elephas-Mammuthus lineage. Soon after the separation of the Elephas lineage and Mammuthus lineage took place during the Pliocene time period. Very little evolution has occurred within the Loxodonta genus in the past two and a half million years, since the only ancestor of the living Loxodonta africana is Loxodonta adaurora. The Elephas lineage however has numerous events of evolution within the genus. According to Maglio’s phylogenetic tree, Elephas ekorenisis is the ancestor of all species in the Elephas genus. From E. ekorenis evolved two new species about 4 million years ago (mya), E. recki and E. hysudricus. Living E. maximus evolved from E. hysudricus approximately 1.8 mya, and from E. recki evolved three more Elephas species: E. falconeri, E. namadicus, and E. iolensis; all of which are extinct.
In a different study performed by Beden (1979), the evolution of Elephantidae occurred differently than what Maglio suggests. Beden suggests that the common ancestor of all elephants is the Stegotetrabelodon, not the Primelephas as Maglio suggests. Beden’s phylogenetic analysis of Elephantidae shows that two clades evolved from the Stegotetrabelodon approximately 5.5 mya: a Loxodonta clade and a Primelephas clade. Within the Loxodonta clade, Loxodonta sheideri is the ancestor of all later Loxodonta species, which would evolve into two species, L. adaurora and L. exoptata, around 4.9 mya. From L. exoptata evolved L. atlantica angammensis about 2.2 mya, then L. atlantica atlantica around 0.8 mya, then to the living L. africana around 0.2 mya. Within the Primelephas clade, Beden supports that Mammuthus and Elephas evolved...