Gorillas are physically the largest of the living great apes and have recently been divided into two species: western gorilla (Gorilla gorilla) and eastern gorilla (Gorilla beringei) as represented by their separate geographical locations in Africa. These species have currently been split into 4 subspecies. Adult male gorillas weigh 135-180kg and average 1.8m tall with an arm span up to 2.6m; females are smaller and often half this weight. They have thick hair covering most of their body; the color varies according to species/subspecies. Like chimpanzees, they are knuckle-walkers but can walk on two legs whilst carrying food or to defend themselves. Gorillas live in a range of habitats from montane (mountain gorillas) to lowland forests (lowland gorillas). Their diet is largely foliage, fruit and sometimes insects. Social groups are led by an adult male or silverback and multiple females and their offspring. They are highly intelligent with the capacity for emotion and building strong family bonds. Average lifespan is 35-40 years, but 55 years has been recorded in captivity.

About 60% of human genes are projected onto the gorilla genome in the current build from Ensembl. Small frame-shifts are adjusted for, larger ones are more problematic. The gorilla genome has 2,8Gb with 20,962 protein-coding genes and 35,727 predicted transcripts.