Final answer:
Neandertals and anatomically modern Homo sapiens were sympatric in Europe for around 2,600 to 5,400 years. The overlap began roughly 50,000 years ago when Homo sapiens entered Europe and ended when Neandertals disappeared approximately 40,000 years ago. Their coexistence and partial interbreeding are evidenced by Neanderthal DNA in modern humans.
Step-by-step explanation:
Neandertals and anatomically modern Homo sapiens were sympatric in Europe for approximately 2,600 to 5,400 years. Evidence indicates that Neandertals lived in Europe and western Asia from around 200,000 to 30,000 years ago. The arrival of Homo sapiens sapiens, around 50,000 years ago, marked the beginning of their coexistence. This period overlapped during a time of significant climatic changes and migration patterns. Both species interacted, as suggested by the presence of Neanderthal DNA in modern humans, which ranges from 1 to 4 percent in European and Middle Eastern populations. The exact reasons for the disappearance of Neandertals around 40,000 years ago are still debated, but theories include climate change, disease, competition with anatomically modern humans, and low genetic diversity in Neandertal populations.
In addition to the environmental and competitive pressures, the Neanderthal genome revealed a lack of diversity and signs of inbreeding, which could have contributed to their decline when facing the adaptable and technologically advanced Homo sapiens.