64 MILLION YEARS AGO

A study of 500 metre-deep core samples from sediments along New Jersey's coastline by a team of scientists led by Professor Kenneth Miller suggest sea levels rose and fell frequently by tens of metres soon after the asteroid hit the planet. Such fluctuations were only possible if the Earth was not free of ice at this time. So it seems something was making the planet very cold and very hot in a short period of time to ensure ice remained in the polar regions but could melt sufficiently in vast quantities to raise the sea level, but not enough time to see all the ice melt. Perhaps the combination of intense cold of the mini-Ice Age had persisted in the winter time and the global warming conditions kicked in during the summer time allowed for this great variability in ocean levels. The team made this interesting discovery after studying the type of sediment, the fossils it contained, and changes in the amount of isotopes in different elements within different layers of the sediment core. (1)

62 MILLION YEARS AGO

The air is fairly clean of dust and soot from the last asteroid impact. World climate has stabilised and oceans levels have not fluctuated, making it easier for some animals to return to the coast to rely on food from the oceans.

At the same time, there came into existence one of the earliest known members of the primate lineage. Known as Purgatorius and belonging to a group called plesiadapiforms, these small mammals made full use of the open environment free of oversized and terrible reptilian predators. About the size of a modern mouse based on analysis of fossilized teeth, jaws, and a few ankle bones dated to this time frame, Purgatorius originated mainly from Montana and Saskatchewan in regions that were covered in dense, humid forests during the early Paleocene. These forests were recovering and rapidly expanding after the mass extinction event, creating a rich environment full of insects, fruits, and new plant growth. The structure of its ankle bones shows that Purgatorius was arboreal, meaning it spent most of its time in the trees rather than on the ground. And as a nimble tree‑dweller, it likely moved through branches in search of food and avoided predators on the forest floor. Its lifestyle probably resembled that of modern tree‑shrews or small primates — active, quick, and opportunistic.

Studies of its teeth show that Purgatorius had a generalized, omnivorous diet. Its molars were shaped for grinding and crushing, suggesting it ate a mix of fruits, seeds, and insects. This flexible diet would have helped it survive in a changing post‑dinosaur world and take advantage of the new plant life spreading through Paleocene forests.

With no older fossilized mammal found to this period, Purgatorius sits right at the base of the primate family tree, which means humans are likely to be the descendants of this species. By occupying arboreal niches and eating a varied diet, it helped set the stage for the later evolution of true primates, including lemurs, monkeys, apes, and eventually humans. Furthermore, its appearance so soon after the dinosaur extinction shows how quickly mammals diversified once the dominant reptiles were gone.