The history of human migration can be tracked by analysing mitochondrial DNA - Edexcel - GCSE Biology - Question 5 - 2016 - Paper 1

During the Ice Age, conditions became harsher, which forced human populations to migrate in search of warmer climates and more accessible food sources.

1. There was an increased or forced migration as humans sought to move further away from cold regions.
2. Sea levels dropped significantly due to massive amounts of water being locked up in ice, which created land bridges that facilitated migration.
3. Frozen seas and ice sheets made some areas impassable, while others became accessible, leading to shorter sea crossings and new routes for human movement.