What general effect did the ice ages have on human migration?

The ice ages had a significant impact on human migration patterns predominantly because they led to the creation of land bridges. During these periods, the Earth's climate cooled, causing large amounts of water to be trapped as ice in glaciers. This resulted in lower sea levels, which exposed previously submerged land, such as the Bering land bridge connecting Asia to North America.

This land bridge provided a route for early humans to migrate into new territories. As groups of humans followed herds of animals across these land bridges, they expanded their range and migrated to areas that were previously inaccessible. This allowed for the spread of humans into diverse environments, leading to various adaptations over time.

The other options describe effects that might not be directly linked to the ice ages in relation to human migration. Increased ocean levels are generally associated with warming periods rather than ice ages, while decreased biodiversity and isolation of populations can occur as a result of migration patterns, but these are more secondary effects rather than direct results of the ice age conditions that created land bridges.