Gorillas have plenty of subcutaneous fat, where Zihlman et al report 13% and 16% in two female gorilla from a paper in 2000^[1], and total body fat up to 44% (Zihlman and McFarland, 2000).

The water-adaptations in Australopithecus afarensis and Australopithecus anamnesis before that include a thick layer of subcutaneous fat, which contrasts to the chimpanzee lineage that has very little total body fat and almost no subcutaneous fat.

So, a shared trait in humans and gorillas, is that both store fat, and also large amounts of subcutaneous fat.

Introgression of genes for storing fat from gorillae to the human lineage, 6–4 million years ago

The gorilla lineage may be a result of the Ethopian plateau forming, from compression of the contintental crust at the Afar tripple junction, which later by extension formed the Afar rift as well as the east african rift. At high elevations above the frost line, there is less fruit, and it is also colder, and so a lot of body fat, as well as adaptations to forage stems and leaves, are natural to that environment.

The Danakil micro-continent broke away from Ethiopia around 6 million years ago, and it is plausible that there were gorilla ancestors, since the island would have been quite large, 500 km from north to south. When isolated, island gorillas would then have mated with Ardipithecus, which led to the Paranthropus lineage where P. deyiremeda^[2] is the earliest Paranthropus in the fossil record.

References

1. Zihlman, A. L., & McFarland, R. K. (2000). Body mass in lowland gorillas: a quantitative analysis. American Journal of Physical Anthropology, 113(1), 61–78.

2. New species from Ethiopia further expands Middle Pliocene hominin diversity (2015)