Anacondas became massive 12 million years ago and their size never changed

Anacondas Became Massive 12 Million Years Ago and Their Size Never Changed (Representational Image: Canva)

A quiet river at dusk can feel ancient. It carries hints of creatures that lived long before us. A new study now shows one such survivor, the anaconda, has stayed giant for millions of years.

Anacondas have kept massive sizes for ages, researchers say. The new findings appear in the Journal of Vertebrate Paleontology on 1 Dec. The study shows ancient anacondas lived during warm Miocene wetlands. They grew large in lush habitats across ancient South America. Researchers say these huge snakes lived around 12.4 million years ago. Fossils suggest their size hardly changed across long periods.

Scientists from Cambridge led the detailed fossil work. They measured 183 fossil vertebrae from old anacondas in Venezuela. These bones came from at least 32 different anaconda individuals. The team used ancestral state tools to check old body sizes. They compared ancient traits with close modern snake relatives. Their model placed early anacondas at around 17 feet long. This length appears close to modern anaconda sizes today.

The team hoped to find even bigger ancient snakes. Warm Miocene climates made many animals very large. Giant crocodiles and huge turtles lived widely during that time. Many of these species later vanished as the world cooled. Study co-author Andrés Alfonso-Rojas said these giants died out as wetlands shrank. But anacondas stayed large despite these massive habitat shifts. He called them “super-resilient” in a released statement.

Modern anacondas still reach impressive lengths in Amazon regions. They average around 13 to 16 feet in length today. Some rare individuals can grow to nearly 23 feet long. Yet scientists wondered if ancient ones grew past that measure. The study found no sign of a snake longer than modern giants. The results surprised the researchers, who were expecting lengths near 26 feet. Fossils offered no proof of any larger ancient anaconda.

Researchers say climate alone may not explain their size. Warm Miocene climates helped early anacondas grow large quickly. But later cooling did not push them to shrink. Their ranges changed, yet their size stayed similar. This suggests size pressure came from other long-term factors.

Food competition seemed unlikely to shape their size, researchers note. Early anacondas faced low competition for prey in ancient wetlands. But they stayed large even when new predators entered South America. These predators spread during Pliocene and Pleistocene shifts. The snakes did not shrink as new rivals filled those ecosystems. The study says prey access alone did not decide their size patterns.

Scientists now say anacondas may hold clues to long-term resilience. Their stable size hints at deep ecological strength. Their history shows how some species endure harsh changes. The study adds new insight into one of Earth’s great predators.