According to this paper, a hidden Markov model of the divergence between humans and chimps finds “a very recent speciation time of human-chimp (4.1 ± 0.4 million years)”. This would put the last common ancestor with Pan after a previously
reported date of between 4.98 and 7.02 million years. (TimeTree reports the weighted average for the time of nuclear divergence to be 5.56 million years). The age of 4.1 million years would apparently put the split during the time of such taxa as Australopithecus anamensis, A. afarensis and Kenyanthropus platyops. It will be interesting to see how this affects our current understanding of hominid evolution.
Ref: Hobolth A, Christensen OF, Mailund T, Schierup MH (2007) Genomic Relationships and Speciation Times of Human, Chimpanzee, and Gorilla Inferred from a Coalescent Hidden Markov Model. PLoS Genet 3(2): e7 doi:10.1371/journal.pgen.0030007