As women age, they tend to replace their husbands—with their daughters. A new study finds that when women hit their 40s, their closest confidant shifts from their spouse to a woman about 25 years younger—presumably a daughter. Researchers analyzed almost 2 billion cell phone calls and 489 million texts to come to their conclusions, identifying the first and second "best friends" of each participant based on who he or she called and texted most often, the Los Angeles Times reports. During early adulthood, No. 1 for both men and women tended to be a same-aged member of the opposite sex, most likely a significant other.
But by their 40s, women tended to shift attention to daughters, as the male moved to the No. 2 position. Meanwhile, women remained in the No. 1 position for men, with either a presumed daughter or son—no preference was shown—occupying the No. 2 slot. Researchers say evolution could explain the findings: Women tend to help with grandchildren in order to ensure their genes survive, while men are able to reproduce later in life than women and thus may have more of an interest in keeping a female in the top spot.