Topic: Biology

Scientists found tiny fossils of Purgatorius in Colorado. This helps us understand how primates evolved and spread across North America.

Scientists have discovered tiny fossils of Purgatorius, the earliest known relative of all primates, including humans. These fossils were found in a southern part of North America than ever before. The discovery is giving us fresh insight into how primates first evolved and spread across the continent.

Purgatorius was a small mammal about the size of a shrew. It appears in the fossil record shortly after the dinosaurs went extinct around 65.9 million years ago. This species is widely considered the oldest archaic primate.

The origins and early geographic history of primates have long sparked debate among researchers. The discovery of these fossils helps fill the gap in understanding the geography and evolution of our earliest primate relatives.

Fossilized ankle bones show that Purgatorius likely lived in trees. Researchers once suspected its absence south of Montana might be linked to widespread forest destruction caused by the asteroid impact 66 million years ago. However, this new discovery suggests that archaic primates originated in the north and then spread southward, diversifying soon after the mass extinction at the end of the Cretaceous Period.

To search more thoroughly for these tiny fossils, researchers used an intensive screen washing process to sift through sediment. This effort was supported by a nearly $3 million collaborative grant from the National Science Foundation. Students and volunteers painstakingly washed and sorted through large amounts of sediment. Their work uncovered numerous fossils of fish, crocodilians, and turtles and eventually several tiny Purgatorius teeth small enough to sit on the tip of a baby's finger.

The discovery also suggests that the apparent absence of early primate relatives in more southern parts of the Western Interior may have been influenced by sampling bias. For nearly 150 years, paleontologists in this region have relied largely on surface collecting methods, which tend to yield larger fossils visible to the naked eye while tiny specimens remain hidden.

Why It Matters

This discovery helps us understand how life recovered after the mass extinction that ended the age of dinosaurs. It also shows how scientists can learn more about our ancestors by studying tiny fossils.

Key Facts

• Purgatorius was a small mammal about the size of a shrew.
• The fossils were found in Colorado's Denver Basin at the Corral Bluffs study area.
• The discovery helps fill the gap in understanding the geography and evolution of our earliest primate relatives.
• Fossilized ankle bones show that Purgatorius likely lived in trees.
• The National Science Foundation supported the research with a nearly $3 million collaborative grant.

Key Terms

Purgatorius

A small mammal about the size of a shrew, considered the oldest archaic primate.

Implications

This discovery helps us understand how life recovered after the mass extinction that ended the age of dinosaurs. It also shows how scientists can learn more about our ancestors by studying tiny fossils.