The monkeys that crossed the ocean

A study, in which Daniele Silvestro and Nicolas Salamin from SIB’s Computational Phylogenetics Group at the University of Lausanne participated, shows that the first monkeys to reach South America by sea weighed barely 400 grams.

Killikaike Homunculus frontal
Two extinct monkey skulls from Patagonia (about 20 million years old). The scientific names of the monkeys are Killikaike blakei (left) and Homunculus patagonicus (right). © Marcelo Tejedo

The first monkeys to reach South America from Africa were much smaller than previously thought, according to a study from scientists in Switzerland, Sweden and Argentina. The researchers propose that monkeys rafted across the Atlantic Ocean more than 40 million years ago and weighed just about 400 grams – the mere size of a squirrel. It took them an additional 20 million years to reach the variation of sizes and life forms similar to what we see today, with some species weighting as much as 12 kg.

The spread of monkeys across South America was facilitated by a global warming around 16-14 million years ago. By that time, New World monkeys occurred as far south as Patagonia, the southernmost geographic range across all primates except humans. Global cooling, eventually leading to the onset of ice ages, drove them to extinction in Patagonia from where they disappeared 14 to 10 Ma ago.

“I have been collecting primate fossils for 25 years across several areas of South America and now after combining together all these data, we discovered that New World Monkeys followed the expansion and contraction of tropical forests. This happened over millions of years and followed climate oscillations” says paleontologist Marcelo Tejedor who co-led the study.

The findings presented in this study are based on the analysis of DNA data from modern species as well as a novel method to integrate morphological and geographic data from living and fossil species.

Reference
Silvestro D et al. Early arrival and climatically-linked geographic expansion of New World monkeys from tiny African ancestors, Systematic Biology, syy046,
https://doi.org/10.1093/sysbio/syy046

Read the news in French on the University of Lausanne’s website

Learn more about Nicolas Salamin’s Computational Phylogenetics Group