There are now eight recognized species of great apes, including humans, that are not extinct. Humans, three species of orangutans from Indonesia, two species of gorillas in Africa, and the chimpanzee/bonobo clade in Africa. Humans share the chimpanzee/bonobo clade vis-a-vis orangutans and gorillas, and are a sister clade to both chimpanzees and bonobos rather than being derived from one or the other of those species.
Six extant species of non-human great apes are currently recognized: Sumatran and Bornean orangutans, eastern and western gorillas, and chimpanzees and bonobos. However, large gaps remain in our knowledge of fine-scale variation in hominoid morphology, behavior, and genetics, and aspects of great ape taxonomy remain in flux. This is particularly true for orangutans (genus: Pongo), the only Asian great apes and phylogenetically our most distant relatives among extant hominids. Designation of Bornean and Sumatran orangutans, P. pygmaeus (Linnaeus 1760) and P. abelii (Lesson 1827), as distinct species occurred in 2001. Here, we show that an isolated population from Batang Toru, at the southernmost range limit of extant Sumatran orangutans south of Lake Toba, is distinct from other northern Sumatran and Bornean populations. By comparing cranio-mandibular and dental characters of an orangutan killed in a human-animal conflict to those of 33 adult male orangutans of a similar developmental stage, we found consistent differences between the Batang Toru individual and other extant Ponginae. Our analyses of 37 orangutan genomes provided a second line of evidence. Model-based approaches revealed that the deepest split in the evolutionary history of extant orangutans occurred ∼3.38 mya between the Batang Toru population and those to the north of Lake Toba, whereas both currently recognized species separated much later, about 674 kya. Our combined analyses support a new classification of orangutans into three extant species. The new species, Pongo tapanuliensis, encompasses the Batang Toru population, of which fewer than 800 individuals survive.
From Alexander Nater, et al., "Morphometric, Behavioral, and Genomic Evidence for a New Orangutan Species", Current Biology (2017).
Meanwhile, a 9.7 million year old great ape tooth has reportedly been found in Germany, outside the range of any previously known great ape population.