The Aepycerotinae appears to be one of the most ancient branches of the Aegodontia, having diverged from other bovids in the Miocene. The result is that the Aepycerotinae have had a long independent history, which makes determining their affiliation with the other subfamilies very difficult (they are allied here with the Hippotraginae-Alcelaphinae-Caprinae clade, but not all authors agree with this). The Aepycerotinae first appear in the fossil record 6.5 million years ago; the impala has not changed considerably since then (some authors consider the Miocene impala to be the same species as the modern impala, Aepyceros melampus).

The continued success of this species (and subfamily) is due to its generalist habits. Impala are not specialized for one mode of food acquisition; they will graze when grasses are fresh and growing, but will readily browse on foliage, and even feed on withered leaves during the dry season. This adaptability in feeding strategies allows the impala is able to live at high densities in a range of habitats.

Only males bear the strongly ridged horns; they are lyrate in form, long, and relatively thin. There are no preorbital glands; however, males have a high concentration of sebaceous glands on the forehead. Unique among the Bovidae, impala possess metatarsal glands (on the fetlocks, just above the hooves on the hind legs), which are strikingly marked with a tuft of black hair.