Neandertals are, like any living species, the result of a long period of evolution.
Since the emergence of Homo ergaster, about 2 million years ago, the human body has reached proportions that are suitable for walking for a long period and time: with longer legs and a much taller stature than before.
Human populations became more mobile and roamed new territories, some of which were made accessible by the decline in sea levels during the ice ages.
This human dispersion has produced regional differences through genetic drift, mutation and natural selection: Neandertals emerged in Europe approximately 300,000 years ago.
These populations have not stopped moving and, sometimes, their paths have crossed and they have exchanged their genetic heritage, as was the case in the Middle East between Neandertals and late anatomically modern humans from Africa.