What the scientists are saying…
Girls are hitting puberty younger
Around the world, girls are starting puberty about a year earlier than they did four decades ago, a new study has found. The onset of menstruation (menarche) has traditionally been seen as the marker for female puberty, but the authors of the latest research say this is problematic: firstly because menstruation can begin later than other signs of puberty, and secondly because people may not remember exactly how old they were when they had their first period. So for their analysis, the Danish team took as their marker the development of glandular breast tissue (thelarche). Having examined data from 30 studies for which girls had their breast tissue expertly assessed, they worked out that since 1977, girls have, on average, been reaching this milestone about three months earlier with every passing decade. (There were regional variations, however, with girls in Africa reaching puberty later than those in Europe and the US.) The study didn’t set out to explain why puberty is creeping forward, but the authors suggest that since a higher body mass index has been linked to the earlier development of glandular breast tissue, the “ongoing global obesity epidemic” could be a partial explanation for the observed change in pubertal age.
The wonders of a table cloth
If you want to impress your friends with your culinary skills, dust off your table cloth. In a German study, diners gave higher marks to a bowl of tomato soup when it was served on a simple white and grey checked cloth; they also sat at the table for longer, and polished off more of it. Dimming the lighting, however, had little impact: it just made the soup taste saltier. The study is the latest in the field of “gastrophysics” – assessing how perceptions of taste are affected by the environment. In 2015, for instance, Oxford University researchers found that people enjoy their food more when they eat it with heavy cutlery. People have also been found to rate cheap wine more highly when they are told that it is expensive.
A new way to diagnose cancer?
Scientists have discovered that the genetic mutations that give rise to cancer can occur decades before symptoms appear, raising the possibility of developing an entirely new way of diagnosing the disease, much earlier. For the study, an international team sequenced the genomes of nearly 2,700 tumours. This enabled them to model the typical “life history” of each cancer, and to spot when the crucial “driver” mutations started to occur. They found that there was considerable variation between different forms: with ovarian cancer, the driver mutations began up to 35 years before the disease was diagnosed (suggesting tell-tale signs could have been there as early as childhood); with kidney, bladder and skin cancers, the mutations occurred almost 20 years before diagnosis; but with liver and cervical cancer, it was less than five years. “Unlocking these patterns means it should now be possible to develop new diagnostic tests that pick up signs of cancer much earlier,” said co-author Dr Peter Van Loo, of the Francis Crick Institute in London.
West Africa’s “ghost” people
UCLA scientists have found evidence of a mysterious “ghost population” of ancient humans, who lived in Africa half a million years ago. The evidence has not come in the form of a fossil – but in pieces of their DNA found in people from West Africa today. “We don’t have a clear identity for this archaic group,” said computational biologist Prof Sriram Sankararaman. “That’s why we use the term ‘ghost’.” This population probably split from the lineage that led to Homo sapiens, Denisovans and Neanderthals as much as 1.2 million years ago, he said. The ancestors of Denisovans moved east, and those of Neanderthals migrated west – but it seems the mystery population stayed in Africa, where Homo
sapiens evolved. The “introgression” between the ghosts and the ancestors of modern West Africans could have occurred within the past 125,000 years, around the same time as Denisovans and Neanderthals were mating with humans in Asia and Europe respectively. According to the study, modern West Africans derive between 2% and 19% of their genetic ancestry from this archaic population, just as all non-Africans have inherited DNA from Neanderthals and/or Denisovans.