Some 23,000 years ago, during the coldest part of the last ice age, people walked across the muddy margins of an ancient lake in what is now White Sands national park, New Mexico.
The footprints they left behind have transformed our understanding of when people first reached the Americas. When we reported dates for the White Sands footprints in 2021, our findings were met with controversy. They placed people in North America thousands of years earlier than other widely accepted sites.
