Forty years of human wonder

We all have birthdays. Certain birthdays, such as 21, 30, 40, 50, 60, 80, 90, 100 are special and are celebrated with festivities. But earlier week, a woman's fortieth birthday was celebrated world over. For that, she is not a political leader, popular sportsperson, or a famous musician. Her birth was a phenomenon. Who is she? and what is the significance of her birth?