A recent paper by Dunbar: https://link.springer.com/article/10.3758/s13423-016-1122-6
Altruism in Chimps: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1896184/
Some of Pat Randolph-Quinney's work: https://scholar.google.co.za/citations?user=kAIFg44AAAAJ&hl=en
Dunbar, R. & Aiella, L. 1993. Neocortex Size, Group Size, and the Evolution of Language. Current Anthropology, 34:2, 184-193.
Gardner, A. 1989. Teaching Sign Language to Chimpanzees. Albany: State University of New York Press.
Wild Chimp gestural communication: https://research-repository.st-andrews.ac.uk/bitstream/handle/10023/4445/2011_HobaiterByrne_gesture_repertoire.pdf?sequence=1