People who do not take up anything spiritual remain 27 years old even if they live to be 100.

Rudolf Steiner: "After this, the human race got younger and younger. By the beginning of the fifth post-Atlantean age, in the fifteenth century, humanity was only able to develop up to the age of 28, with no further development after this, and today we have reached a point where people only reach the age of 27, if this is left to nature. In the past, human beings naturally remained capable of development into a ripe old age. Today people must conclude such development as comes of its own accord and is tied to the physical body by the age of 27, unless they take up a spiritual impulse in their inner life and push on from within. People who do not take up anything spiritual remain 27 years old even if they live to be 100. It means they have the characteristics of 27-year-olds. And with people refusing to look for inner spiritual impulses, we now have a culture and a social life that is 27 years of age. We do not grow beyond the age of 27 in our outer social life. This age now rules humanity. If we go on like this, humanity will go down to 26, 25, and 24 years, then in the sixth post-Atlantean age to the twenty-first, and later to the fourteenth year."