While tusks are a defining feature of the species, not all elephants grow them due to a combination of natural biological factors and external pressures. Elephant tusks are actually highly specialized, elongated incisor teeth that project far beyond the mouth of the animal. The absence of tusks stems from inherent genetic variation present in elephant populations, which has been dramatically amplified by human activity.
The Biological Nature of Tusks
Elephant tusks are not horns but are considered living tissue, developing from the upper jaw’s second incisor teeth, which begin to emerge around the age of two or three years. They grow continuously throughout an elephant’s life, reaching lengths of up to 10 feet in some African elephants. The bulk of the tusk is composed of dentine, a hard, dense material that makes up the ivory, while a thin cap of enamel covers the tip when the elephant is young, though this typically wears away with age.
Inside the tusk is a deep pulp cavity containing nerves and blood vessels, making the structure sensitive to damage. Tusks serve multiple purposes in the wild, including digging water holes and unearthing minerals and salts from the soil. They also aid in foraging by stripping bark from trees and lifting heavy objects, while functioning as weapons for defense and displays of dominance.
Standard Tusk Distribution Across Species and Sexes
The presence and size of tusks vary significantly between the two main types of elephants: African and Asian. In African elephants, both sexes typically develop visible, external tusks, though the tusks of mature males are generally thicker and longer than those of females.
The pattern is markedly different among Asian elephants, where tusks are primarily a characteristic of males. Only a small percentage of female Asian elephants grow short, vestigial tusks known as “tushes,” or they are entirely tuskless. Furthermore, a substantial number of male Asian elephants, called “makhnas,” also naturally lack tusks, demonstrating that tusklessness is a long-established, normal variation within that species.
Natural Tusklessness: The Role of Genetics
Tusklessness occurs naturally in all elephant populations, but in African elephants, it is a rare, inherited trait that has been the subject of recent genetic study. Researchers have linked the condition in African savanna elephants to a dominant genetic change located on the X chromosome. This X-linked nature explains why tusklessness is observed almost exclusively in females.
The genetic change is hypothesized to be a male-lethal trait, meaning that male elephant fetuses who inherit the gene are likely to spontaneously abort. Studies point to the involvement of genes like AMELX, which is associated with tooth development and enamel formation, and which, when mutated, causes similar dental defects in humans. This strong selection against tusked males maintains the trait predominantly in the female population.
Human Influence: Poaching and Accelerated Evolution
While genetics provides the foundation for tusklessness, illegal ivory poaching has acted as a powerful selective force, dramatically accelerating the frequency of the trait. Poachers historically target elephants with the largest tusks for the ivory trade, effectively removing tusked elephants and their genes from the breeding population. In this scenario, tuskless elephants possess a distinct survival advantage because they are not the target of hunters, allowing them to live longer and pass their tuskless genes to the next generation.
This phenomenon is a clear example of rapid, human-induced evolution, often referred to as artificial selection. A striking example occurred in Mozambique’s Gorongosa National Park, where intense poaching during the civil war (1977–1992) caused the elephant population to plummet by 90%. Before the conflict, approximately 18.5% of female elephants were tuskless, but immediately afterward, that number soared to over 50%.
The elevated percentage of tuskless females has persisted in subsequent generations, with about 33% of females born since the war also lacking tusks, confirming the heritability of the trait. Statistical modeling showed that tuskless females in Gorongosa were five times more likely to survive the poaching period than their tusked counterparts. This effect is also visible in other heavily poached areas, such as South Africa’s Addo Elephant National Park, where nearly 98% of the female population was reported as tuskless in the early 2000s.