They are mum’s first gift to her newborn baby on the day of its zeroeth birthday – bacteria, fresh from her vagina. Vaginal bacteria are among the trillions of microscopic hitchhikers that share our bodies with us. Collectively known as the ‘microbiota’, these passengers outnumber our own cells by ten to one. Children partly inherit their microbiota from their mothers. During birth, they pass from the largely bacteria-free conditions of the womb through the microbe-laden vagina into the equally bacterial outside world.
Being slathered in vaginal microbes might not seem like much of a treat from our adult perspective, but to a newborn, it’s a key event. The microbiota are important partners, influencing our physiology and our risk of disease. Now, Maria Dominguez-Bello from the University of Puerto Rico found that the way we enter the world determines the identities of our first bacterial colonisers. Babies delivered by Caesarean section end up with a very different portfolio to those who are born naturally.
Discriminating against people who do not speak your language is a big problem. A new study suggests that the preferences that lead to these problems are hard-wired at a very young age. Even five-month-old infants, who can’t speak themselves, have preferences for native speakers and native accents.
The human talent for language is one of our crowning evolutionary achievements, allowing us to easily and accurately communicate with our fellows. But as the Biblical story of the Tower of Babel relates, linguistic differences can serve to drive us apart and act as massive barriers between different social groups.
These barriers can give rise to linguistic discrimination, a far more insidious problem that it seems at first. Language-based prejudices have led to horrific acts of human abuse, and even civil wars. Genocide often finds itself paired with linguicide, since a race can be killed off more thoroughly if their language follows them.
Even today, people in a linguistic minority can find themselves denied access to healthcare, or at a disadvantage when looking for jobs. The issue cuts to the heart of several ongoing debates, from the role of second languages in education to whether immigrants must become fluent in the tongue of their host country.
It should therefore be unsurprising to learn that we have strong preferences for our own language and for those who speak it. But Katherine Kinzler and colleagues from Harvard University, have found that we develop these preferences from an incredibly young age, before we can speak ourselves, and well before we can even hope to understand the social issues at stake.
Popularity is a fickle thing. Styles, products, social movements and people can be bathing in the spotlight one day and languishing in obscurity the next. And according to a new study, things that catch on most quickly are also abandoned most easily – the faster the rise to prominence, the steeper the fall from grace.
Many researchers have looked into the reasons behind the success of cultural tastes, but Jonah Berger and Gael Le Mens were more interested in the factors that drive them to extinction. To examine that, they looked at the changing popularities of first names in France and the USA over the last 100 years. They found that names that suddenly became popular lost their appeal just as quickly, while those that became more steadily used had more sticking power.
Charlene, for example, became slowly more popular from the turn of the 20th century, peaked in 1950 and declined slowly after. Tricia and Kristi experienced faster rises in the 50s and 60s and fell equally sharply in the 70s and 80s. At their peaks, all three names accounted for around one in every 500 female births in the US, but Charlene had a much larger impact over time because of the slower pace of its change.
It seems that parents are (quite rightly) concerned that fad names will eventually be short-lived. As Berger and Le Mens say, “They may avoid such items to avoid doing something that may later be seen as a flash in the pan.” Of course, that very concern ensures that fast-rising items do become short-lived fads in a very self-fulfilling way.
Our health isn’t just affected by the things we do after we’re born – the conditions we face inside our mother’s womb can have a lasting impact on our wellbeing, much later in life. This message comes from a growing number of studies that compare a mother’s behaviour during pregnancy to the subsequent health of her child.
But all of these studies have a problem. Mothers also pass on half of their genes to their children, and it’s very difficult to say which aspects of the child’s health are affected by conditions in the womb, and which are influenced by mum’s genetic legacy.
Take the case of smoking. Doing it while pregnant is bad news for the foetus, and studies have suggested that children whose mothers smoke during pregnancy are more likely to be born prematurely, be born lighter, have poorer lung function, and be more likely to die suddenly before their first birthday. More controversially, they may even show higher levels of behavioural problems including autistic disorders and antisocial tendencies.
Biologically, these results make sense, but many of these risks can be inherited too. For example, genetic factors can strongly influence both a person’s susceptibility to nicotine addiction and their propensity for violent behaviour. A mother’s genes could also affect the birth weight of her child.
To untangle these influences, the ideal experiment would involve randomly implanting foetuses either in the wombs of their own mothers, or those of unrelated women. That’s possible in animals but deliberately doing so in humans would be both unethical and impractical. Nonetheless, Frances Rice from Cardiff University realised that this experiment was actually well underway.
Since the advent of in vitro fertilisation (IVF) technology in the late 1970s, many mothers have nourished babies in their womb, who weren’t genetically related to them. Here was an ideal chance to study the effects of conditions in the womb, without any confusion caused by shared genes.