CORVALLIS, OREGON — A massive wall of ice may have stopped the first people entering the Americas doing so via the land bridge that connected it with Asia, according to a study in the Proceedings of the National Academy of Sciences, which instead suggested they likely arrived via boats along the Pacific coast.


Previous research has suggested an ice-free corridor between the ice sheets that covered North America at the time may have allowed for travel from Beringia, the landmass that connected Asia with North America, down to the Great Plains.


However, analysis of geological samples from six locations found that the ice-free corridor did not fully open until about 13,800 years ago, whereas, according to Live Science, previous studies have discovered stone artifacts in central Mexico that were at least 26,500 years old, which would mean these earliest immigrants’ path would’ve been blocked by ice sheets.


These sheets may have been between 1,500 and 3,000 feet, or 455 to 910 meters high, according to the new study, which makes them taller than any building on Earth.