At Gizmodo, Margherita Bassi reports on new insights into how Neanderthals crossed Asia speedily:

Our prehistoric cousins likely first reached Asia around 190,000 to 130,000 years ago, with another substantial migration to Central and Eastern Eurasia likely between 120,000 and 60,000 years ago. But how did they get there?

“Neanderthals Spread Across Asia With Surprising Speed—and Now We Know How,” June 14, 2025

An agent-based computer study in PLOS One suggests that they followed river systems:

Since there isn’t enough archaeological evidence to reconstruct their migration paths, a team of anthropologists has turned to computer models. Their simulations mapped out possible routes Neanderthals could have followed to reach Asia, and suggest that by traveling during warmer periods and following river valleys, they could have traversed approximately 2,000 miles (3,250 kilometers) in less than 2,000 years.

“Our findings show that, despite obstacles like mountains and large rivers, Neanderthals could have crossed northern Eurasia surprisingly quickly,” Emily Coco, co-author of a study published yesterday in the journal PLOS One, said in a New York University statement. “These findings provide important insights into the paths of ancient migrations that cannot currently be studied from the archaeological record and reveal how computer simulations can help uncover new clues about ancient migrations that shaped human history.” Coco began the study as a doctoral student at New York University and is now a postdoctoral researcher at the University of Algarve. “Now We Know How”

Of course, if they followed river systems, they were assured of sources of food and water along the way.

From the open-access study:

Here, we apply agent-based least-cost path simulations for the first time to Neanderthals, showing that they most likely took a northern route through the Urals and southern Siberia under all climate scenarios. Agents leaving either the southern or the northern Caucasus Mountains reach the Altai in less than 2000 years during two time windows when the climate was mild, in MIS 5e (the Last Interglacial) and in MIS 3. The latter coincides with the dated presence of Neanderthals at Chagyrskaya and Okladnikov Caves in the Altai.

Coco E, Iovita R (2025) Agent-based simulations reveal the possibility of multiple rapid northern routes for the second Neanderthal dispersal from Western to Eastern Eurasia. PLoS One 20(6): e0325693. https://doi.org/10.1371/journal.pone.0325693