Anacondas became massive 12 million years ago — and it worked so well, they haven't changed size since

A long blackish snake coiled upon itself on the grass.

Anacondas have been giant for millions of years, a new study finds.

The enormous snakes' average body size has remained constant since they first appeared in the fossil record about 12.4 million years ago, during the Middle Miocene (16 million to 11.6 million years ago), researchers revealed in a new study published Monday (Dec. 1) in the Journal of Vertebrate Paleontology.