Final answer:
Neandertals, or Homo neandertalensis, were stocky and robust with a distinctive physical build adapted to cold climates. They lived approximately 400,000 to 30,000 years ago and interbred with modern humans.
Step-by-step explanation:
The Neandertals (Homo neandertalensis) were an extinct species of archaic humans that lived in Europe and Asia between about 400,000 and 30,000 years ago. They evolved from Homo erectus and were distinctly adapted to the cold climates of these regions. Contrary to the stereotypical depiction of Neandertals as brutish cavemen, they were intelligent and capable of using complex tools, controlling fire, and they had social practices such as burying their dead. From the information provided, it is clear that Neandertals were stocky and robust, with a barrel-chested physique, not tall and thin or walking on four legs, and certainly not genetically abnormal modern humans. These physical characteristics, including a flat skull with a rounded back and a pronounced brow ridge, along with their massive musculature and jaws, suggest they were powerfully built for survival in their environment. It is also noteworthy that Neandertals interbred with anatomically modern humans, contributing to the genetic diversity of contemporary human populations.