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Evolutionary history

About 40 million years ago, the Simiiformes infraorder split into the parvorders Platyrrhini (New World monkeys) and Catarrhini (apes and Old World monkeys) somewhere on the African continent. Platyrrhini are currently conjectured to have dispersed to South America on a raft of vegetation across the Atlantic Ocean during the Eocene epoch, possibly via several intermediate now submerged islands. Several other groups of animals made the same journey across the Atlantic, notably including caviomorph rodents. At the time the New World monkeys dispersed to South America, the Isthmus of Panama had not yet formed, so ocean currents, unlike today, favoured westward dispersal, the climate was quite different, and the width of the Atlantic Ocean was less than the present 2,800 km (1,700 mi) width by about a third (possibly 1,000 km (600 mi) less, based on the current estimate of the Atlantic mid-ocean ridge formation processes spreading rate of 25 millimetres per year (1 in/year)).

The non-platyrrhini Ucayalipithecus of Amazonian Peru who might have rafted across the Atlantic between ~35–32 million years ago, are nested within the extinct Parapithecoidea from the Eocene of Afro-Arabia, suggesting that there were at least two separate dispersal events of primates to South America, Parvimico and Perupithecus from Peru appear to be at the base of the Platyrrhini, as are Szalatavus, Lagonimico, and Canaanimico.

Possible evidence for a third transatlantic dispersal event comes from a fossil molar belonging to Ashaninkacebus simpsoni, which has strong affinities with stem anthropoid primates of South Asian origin, the Eosimiidae.

The chromosomal content of the ancestor species appears to have been 2n = 54. In extant species, the 2n value varies from 16 in the titi monkey to 62 in the woolly monkey.

A Bayesian estimate of the most recent common ancestor of the extant species has a 95% credible interval of 27 million years ago - 31 million years ago.