Humans adapt to changes in the environment by genetic change, developmental adjustments, acclimatization, and cultural or technological advances. Of these, the fourth is almost uniquely human and has been the key to the species' success worldwide.
Genetic change in humans is slow, but it is known to occur. In Europe, during the last ice age, a variety of humans called Neanderthals developed a number of cold-weather adaptations that presumably helped them survive in the frigid climate. Among these were a stocky frame, large noses for efficient heat exchange and thick, robust bones that permitted the attachment of large muscles.
Developmental adjustments are faster than genetic evolution, as they play out on a generational scale. After World War II, for example, the common diet of Japanese people changed to include more animal protein. While this had no effect on Japanese adults, their children and grandchildren grew faster during childhood to an average of 7 inches taller.
Acclimatization is even faster than developmental adjustments and can work within a single individual's lifetime. An example of this is the body's ability to add and shed fat in response to a changing diet.
Cultural and technological changes are among the most complex adaptations humans use. Clothes, fire and radio communications are all technologies humans have developed as insulation against the demands of the natural world.