A groundbreaking study has revealed that early primates evolved in cold climates, not in the tropical jungles long believed to be their birthplace. Instead of warm, lush forests, these ancestors of monkeys, apes, and humans likely adapted to seasonal environments with freezing winters and hot summers in what is now North America.
The findings, published Tuesday in the journal PNAS, challenge a long-standing theory in evolutionary biology. For decades, scientists assumed primates emerged in tropical regions, but new evidence shows their origins lie in much harsher, colder conditions around 66 million years ago.
Researchers at the University of Reading reached this conclusion after combining fossil records with advanced statistical models to reconstruct ancient habitats.
They found that the earliest primates thrived in areas that experienced dramatic seasonal changes—overturning the so-called “tropical forest hypothesis” that has shaped scientific thinking for generations.
New research challenges long-held evolutionary theory
Lead author Dr. Jorge Avaria-Llautureo said the idea that primates began in tropical climates had gone unchallenged for years, but their research offers a different story. He explained that instead of evolving in jungles, these animals likely adapted to cold, northern landscapes marked by extreme weather shifts.
Understanding how ancient species responded to changing environments could also provide valuable insight into how modern primates—and even humans—might cope with today’s rapidly shifting climate, Avaria-Llautureo added.
The study also highlights how movement across different habitats played a critical role in primate survival and evolution. Primates that were able to travel far when their local climate became unstable had a better chance of surviving and producing offspring that evolved into new species.
The research indicates that individuals who relocated to entirely new and stable environments migrated an average distance of approximately 561 kilometers (349 miles).
In contrast, primates that remained in unstable but familiar regions moved only about 137 kilometers (85 miles).
Mobility and climate change helped shape new species
Another surprising theory from the team suggests that early primates may have survived extreme winters by hibernating, similar to modern bears.
Some living species still use this tactic today. For example, dwarf lemurs in Madagascar dig into the ground and enter a deep sleep during colder months, sheltering beneath roots and layers of leaves to stay warm and conserve energy.
The study concludes that early primates didn’t enter tropical rainforests until much later in their evolutionary journey. They moved step by step—from cold regions to milder zones, then into dry landscapes, and eventually into the hot, humid forests where many now live.
These shifts, often driven by sudden changes in temperature or rainfall, forced primates to adapt or relocate, helping spark the development of new species.
By showing that early primates evolved in cold climates, the study rewrites a key chapter in the story of human and animal evolution.
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