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This week, science explains the chemical love-connection we share with our dogs, and how some of the most isolated populations of people in the world are different on the inside.

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Sources:
http://www.sciencemag.org/lookup/doi/10.1126/science.1261022
http://www.sciencemag.org/lookup/doi/10.1126/science.aab1200
http://www.eurekalert.org/jrnls/sciadvances/pdf.php?date=2015-04&file=clemente150417.pdf
http://www.eurekalert.org/emb_releases/2015-04/cp-wlm040915.php
http://www.cell.com/cell-reports/abstract/S2211-1247(15)00340-X
http://www.eurekalert.org/jrnls/cell/pages/pdf/cellreports/CELREP1688_proof.pdf
http://www.eurekalert.org/emb_releases/2015-04/nlmc-umd041315.php
It’s high time we here at SciShow dispel this myth that YouTube is all about cat videos.    The fact is we like dogs as well.   We’ve talked a lot about the science of canines -- like their health, their behavior, and how they evolved alongside humans to become our companions and helpmates and friends.   But this week scientists said they may have pinpointed why humans tend to have deep, emotional bonds with dogs more than any other kind of animal.   It turns out that the hormonal response we have to our dogs is the same chemical connection we have with our own babies!   So, yeah! Those people who dress their dogs up in cozy sweaters, and talk to them in complete sentences, and basically treat them like they’re offspring?   That may not just be a matter of being like “a dog person” -- it may also be a result of oxytocin.   Oxytocin is a hormone released by the pituitary gland, and it’s probably the most important chemical in your body when it comes to relationships.    The secretion of oxytocin has been associated with the feelings of comfort and security; it also fuels intimate behaviors -- especially sex -- but its strongest influence probably has to do with parenting.    Oxytocin is what stimulates contractions during childbirth, produces breast milk during nursing, and both women and men are bubbling over with it when they care for their newborns.   So oxytocin does a lot of different things.   And according to a team of Japanese researchers, people also get amped up on oxytocin when they’re with their dogs.   But instead of being triggered by things like feeding or nurturing, the team found that people and dogs both release oxytocin when they make eye contact with each other.   In one experiment, the researchers put dogs in a room with their owners and watched them interact for half an hour.    They then measured oxytocin levels in the urine of both the dogs and the people, and they found that -- regardless of how much the people interacted with their dogs in other ways, like talking to them or petting them -- the dog-human pairs that had the most eye contact also had the highest levels of oxytocin.   In a second experiment, the scientists gave the dogs a dose of oxytocin and then put them in a room with their human friends, along with some strangers.    The female dogs that had been treated spent much more time maintaining visual contact with their people. And after half an hour of being stared at with adorable puppy eyes, the owners of the treated dogs had higher levels of the hormone, too.   Now, the researchers point out that none of this happens with wild canines -- even wolves raised in captivity don’t show this intimate, hormonal response to the people who raised them.   So this research suggests that humans and dogs have found a way to create a feel-good feedback loop, reinforcing our mutual bonds by driving each other’s levels of love hormone.   A little bit weird? Sure. #cute? Definitely.   There was also some unusual news this week about what’s probably humanity’s second best friend... our gut bacteria!   We’re fond of pointing out here at SciShow that there are more microorganisms in and on you than there are cells in your body.   So you are basically your own ecosystem -- it’s called the human microbiome -- and just like any other exotic habitat, we don’t know all that much about it.    Like, do the bacteria living in your gut change with your particular lifestyle choice? Or are they all the same for everyone?   To find out, two teams of scientists studied some of the most remote populations of people on Earth, to see what’s living inside of them.    In one study, published in the journal Cell, Australian biologists collected gut samples from 40 people living in two villages in rural Papua New Guinea, each village representing a different ethnic group.   Both groups turned out to have radically different bacteria than the average person in the U.S. -- with Papua New Guineans hosting at least 50 different kinds of microbes that Americans lack.   Plus, the microbiomes of both groups of villagers were pretty much the same, whereas the Americans showed more variation from person to person.    And similar results showed up in an even more isolated population:   In this week’s issue of the journal Science Advances, researchers say they studied members of a group known as the Yanomami, who live in the Venezuelan Amazon. This particular group lived in isolation from the modern world until they were first contacted by outsiders in 2008.   When physicians met these Yanomami the following year, they collected samples from 34 of the villagers, and they, too, turned out to be walking around with a totally different gut party going on inside them.   Their gut biota turned out to be 66 percent more diverse than samples from the US, Africa, and more industrialized parts of Venezuela.   They also had microbes that conferred some advantages, like bacteria that are known to inhibit the development of kidney stones.   In the end, both studies conclude that industrialized society may have made great strides in public health -- what with our hand sanitizers, antibiotics, and wastewater treatment. But we’ve also lost some of our natural, microbial diversity.   So in all likelihood, we have far fewer types of invisible companions than our ancestors did.   But … at least now we have our dogs.   And thank you for watching SciShow News! If you want to keep getting smarter with us, you can go to youtube.com/scishow, and subscribe.