Well

Although the 'trichotonomy problem' has been the subject of much debate, both a review of soft tissue anatomy (1) and recent genetic evidence (2,3) have shown that chimpanzees are almost certainly the closest relatives of humans. It is though that gorillas splt only a short time before the homo pan divergence which made the phylogeny difficult to resolve.(1) Sally Gibbs, Mark Collard, and Bernard Wood. Soft-tissue characters in higher primate phylogenetics. 11130—11132 PNAS September 26, 2000 vol. 97 no. 20(2) R. Wimmer, S. Kirsch, G. A. Rappold, and W. Schempp. Direct evidence for the Homo-Pan clade. Chromosome.Res. 10 (1):55-61, 2002.(3) S. L. Page and M. Goodman. Catarrhine Phylogeny: Noncoding DNA Evidence for a Diphyletic Origin of the Mangabeys and for a Human—Chimpanzee Clade. Molecular Phylogenetics and Evolution Vol. 18, No. 1, January, pp. 14—25, 2001.