The mother-child bond has long been known, but new research by a University of Notre Dame Anthropologist shows that dads who sleep near their children change too, through a drop in testosterone.
There have already been numerous studies that show a man's testosterone drops when he marries and drops even more when he has children, suggesting this might make men more responsive to their child's needs.
While most of video in the on-air version of our story is from Notre Dame studies regarding co-sleeping in the United States, Anthropologist, Dr. Lee Gettler did his research in the Philippines.
Co-sleeping in the Philippines is the norm, with 92 % of father's sleeping with their kids.
And Cultural differences, including smaller homes and sleeping on mats made it a perfect location for Dr. Gettler's research.
So in a culture where co-sleeping is the norm, Dr. Gettler made a unique discovery, saying, "We found that men who slept near their kids had lower testosterone than men who didn't."
Sampling more than 360 fathers and measuring a fathers testosterone through saliva samples, Gettler was able to prove that a father's physiology changes through co-sleeping.
He explains, "The hypothesis that we tested is, does fatherhood and care giving relate to lower testosterone and we found that it did. Our interpretation of this from an evolutionary angle is that this is a good thing. It shows that mothers are not the only ones who are kind of biologically responsive to becoming parents and potentially attuned to the needs of their children."
If you're a man, you're probably wondering if a drop in testosterone should worry you. Dr. Gettler says no. "There's some evidence that it might be related to aggressive or competitive behavior so it kind of depends on what men's definition of masculinity is, but the range of testosterone that we're seeing shouldn't impact say a man's ability to have additional children, it's not going to impact their sperm count."
So how does Gettler's research in the Philippines translate to the dads in the U.S., where co-sleeping is not the norm?
Gettler responds, "I think there's a lot of interesting issues about the sleep environment in the U.S. and what fathers do on a day to day basis that suggest it could be the same here, but we really need to test it to be sure."
Through co-sleeping, a man's physiology changes, something long thought exclusive to motherhood. Gettler says, "This research is really showing that women are not the only ones who are biologically responsive to parenthood."
Gettler adds, while co-sleeping has been controversial in the U.S. because of SIDS, or Sudden Infant Death Syndrome, it is different in the Philippines because of the sleep surface and no need for heavy blankets.
But he says the American Academy of Pediatrics does recommend a child sleep in the same room as their parents, in a crib near the bed, for the first six months of life.
Click on the link below if you would like to read Dr. Gettler's study, which was published in the September 5th issue of the Journal, Plos One.
There is also a link to learn more about Dr. Gettler.