For a long time, researchers have tried to nail down just what shapes us—or what, at least

, shapes us most. And over the years, they've had a lot of finding moments. First it was our parents, particularly our mothers. Then it was our genes. Next it was our peers, who show up last but hold great sway. And all those ideas were good ones—but only as far as they went.

The fact is once investigators had exposed all the data from those theories, they still came away with as many questions as answers. Somewhere, there was a sort of temperamental dark matter exerting an invisible gravitational pull of its own. More and more, scientists are concluding that this un explained force is our siblings.

From the time they are born, our brothers and sisters are our collaborators and coconspirators, our role models and cautionary tales. They are our scolds, protectors, goads, tormentors, playmates, counselors, sources of envy, objects of pride. They teach us how to resolve conflicts and how not to; how to conduct friendships and when to walk away from them. Sisters teach brothers about the mysteries of girls; brothers teach sisters about the puzzle of boys. Our spouses arrive comparatively late in our lives; our parents eventually leave us. Our siblings may be the only people we'll ever know who truly qualify as partners for life. "Siblings," says family sociologist Katherine Conger, "are with us for the whole journey."

Within the scientific community, siblings have not been wholly ignored, but research has been limited mostly to discussions of birth order. Older sibs were said to be strivers; younger ones rebels; middle kids the lost souls. The stereotypes were broad, if not entirely untrue, and there the discussion mostly ended.

But all that's changing. At research centers in the U.S., Canada, Europe and elsewhere, investigators are launching a wealth of new studies into the sibling dynamic, looking at ways brothers and sisters steer one another into—or away from—risky behavior; how they form. a protective buffer against family upheaval; how they educate one another about the opposite sex; how all siblings compete for family recognition and come to terms over such impossibly charged issues as parental favoritism.

From that research, scientists are gaining intriguing insights into the people we become as adults. Does the manager who runs a congenial office call on the peacemaking skills learned in the family playroom？ Do husbands and wives benefit from the inter-gender negotiations they waged when their most important partners were their sisters and brothers？ All that is under investigation. "Sib lings have just been off the radar screen until now," says Conger. But today serious work is revealing exactly how our brothers and sisters influence us.

What can be inferred from the last sentence of paragraph 1？

A．Previous findings revealed what shapes us.

B．Previous findings were accurate and trustworthy.

C．Previous findings contributed in a limited way.

D．Previous findings went too far in explanation.