There are hundreds of bacterial(细菌的)species in our stomach. Bacterial diversity is a good thing, a general contributor to and marker of good health. But what does a healthy stomach look like? Studies indicate that the composition varies by many factors.

One of the most important, it turns out, is who you currently live with. Researchers have come to the conclusion: Diet and heritability(遗传力) are known to affect the microbiome(微生物组), but social relationships shape it most—especially when it comes to marriage. The Dutch Project, which studied microbes in 8, 208 individuals belonging to three generations, finds that the heritability of microbes is only 1. 9 percent. They noticed much greater similarity among the unrelated individuals sharing a household than among relatives who do not share households, including twins whose living situations differ in adulthood.

The researchers found that nearly 50 percent of microbial types were significantly affected by cohabitation. In general, the microbiomes of all types of cohabitors (including parents and children) were more similar than those of participants living separately no matter their relatedness. Married couples who report having a close, loving relationship have the most similarity. Evidence of microbial sharing, especially of rare species, shows exchanges through interactions. And that puts highlight on acts of close relationship—including kissing. Scientists have known for decades that social relationships, especially marriage, powerfully affect health. Not only are the microbiomes of cohabiting couples more similar to each other; they also are more similarly diverse. There is a greater richness of species than in unmarried, noncohabiting individuals.

Despite the dominating influence of a close, cohabiting relationship, the microbiome can be different in diet, especially one rich in plant fiber. It can also be influenced by behavior, such as farming and gardening and exercise. Moreover, it’s adaptable to environment—green space and pollutants around you. Living in a rural environment brings increases in bacteria linked to health, and decreases in bacteria that are harmful. Living with pets also has a positive effect on the microbiome, while exposure to air pollution, especially car exhaust, and passive exposure to cigarette smoke have negative effects.

It can also be affected by direct addition of specific species of bacteria, delivered in consumable probiotics(口服益生菌). There are probiotics now marketed for digestive health, others aimed at immune health, and still others for boosting mood. Now that it’s clear that social relations play the largest role in the makeup of the microbiome, can probiotics for singles be far behind?

The start-up that attracted the largest investment in the history of cybersecurity, of more than half a billion dollars, has a simple goal: a passwordless future.

Despite the spread of password management software that can generate and remember complicated strings of random characters, some of the most common passwords are still “12345”, “password” and “iloveyou”. As a result, more than 80 percent of hacks involve these kinds of passwords; and passwords remain the most sought-after data by hackers, above other personal or sensitive information.

In many cases, individuals are tricked into handing over password details by phishing emails and other social engineering techniques. Hackers have sought to break into apps and steal entire password databases as well. Passwords are also under attack from new technology, such as automated programs that can rapidly try to guess them, or can try stolen passwords on multiple online accounts.

Since the need to replace the easily forgotten and highly hackable strings of letters and numbers that we use to access everyday life has become even more urgent, the race to replace the password is under way, with biometric-based (基于生物识别的) security emerging as one of the most sought-after solutions. According to Tieo, a union of more than 250 companies, which promotes a standard system of passwordless authentication (身份验证), the vast majority of consumer services will offer passwordless login systems in the next couple of years. “If done correctly and safely, biometrics are really helping us move to a passwordless future in a rapid manner,” said Andrew Jenkinson, CEO of Tieo.

But there are still risks associated with the use of biometric authentication. Unlike passwords, biometrics cannot be changed. This means such data must be closely guarded for privacy purposes and to prevent spoofing—hackers trying to trick cameras or sensors with photos, or masks of their victim. “Biometric authentication and passwordless authentication has its own attack surface,” said Paul Smith, director of security research at CyberPek. His team revealed that it had found a design problem which would allow potential attackers to bypass facial recognition login by injecting a spoofed photo of a user’s face into the process.

The biggest obstacle standing in the way of the start-ups hoping to kill the password is how to change years of habit. Eric Brown, founder of TAK Cyber, a cyber research and advisory company, argued that while sensitive applications may rapidly shift from passwords, other websites have less motivation to update their systems. “You’ll never get rid of them,” he said. “We’re never going to get to the post-password era.”