Discovered: How mothers become one with their offspring; why elderly people are easier to scam; the past warms the bones; the hidden truth inside ancient rainfall.

Mother and child bonds lingers, down to the cell Even after babies exit the womb, their cells stick around in mothers' brains. Microchimerism—the presence of someone's cells inside the body of someone else—has been demonstrated before, but a new study shows that a surprising 60 percent of mothers have cells from their children lingering in their brains and bloodstream. This finding will interest researchers seeking to understand the correlation between multiple pregnancies and brain diseases like Alzheimer's, which have been observed in many mothers. So far it's unclear what effect baby cells have on mothers. [Scientific American]

Old people have less brain activity in the anterior insula, so they get scammed more. Schemers who target senior citizens already knew this intuitively, and now science confirms that old people are typically easier to fraud. That's the case because as our brains age, our anterior insulas become less active. Neuroscientists have found that whenever we see someone who looks like they're up to no good, this region lights up. And according to new research from Shelley Taylor of the University of California, Los Angeles, diminished anterior insula activity could be instrumental in making the elderly more vulnerable to scams. But what old people lose in wariness thanks to this phenomenon, they make up for in positive outlook: "Older people are good at regulating their emotions, seeing things in a positive light, and not overreacting to everyday problems," says Taylor. [Science Now]

Rain that fell billions of years ago reveals ancient atmospheric conditions. Raindrops may seem like fleeting things, but the marks left by precipitation from 2.7 billion years ago are giving NASA's Sanjoy Som a better understanding of the Earth's early atmosphere. His palaeobarometry method could help those interested in ancient meteorology find out what things were like when the Earth spun faster, with the Moon in closer orbit and the sun much weaker. "The rationale here is that if the air back then was thicker, the raindrops would fall slower, and the craters in the ash would be smaller," says Som, explaining his methods. "And conversely, if the air was thinner, the drops would fall faster and the craters would be larger." [BBC News]

If you need to warm up, just think about your childhood. The etymology of the word nostalgia is Greek, derived from the words for "homecoming" and "pain." But new research suggests that nostalgia isn't painful at all—that it actually makes those longing for the past feel warmer. University of Southampton researchers studied nostalgic thoughts in a group of college students, finding that they reflected on bygone days more in chilly temperatures and that these thoughts gave them a sensation of warmness.  [The Atlantic]