An article published recently in the scientific journal Nature is shedding new light on an important, but so far little has been appreciated, aspect of human evolution. In this article, Professors Dennis Bramble, and Daniel Lieberman suggest that the ability to run was a decisive factor in the development of our species. According to the two scientists, humans possess a number of anatomical (人体结构的) features that make them surprisingly good runners. “We are very confident that strong selection for running, which came at the expense of the historical ability to live in trees — was helpful in the origin of the modern human body form,” says Bramble, a biology professor at the University of Utah.

Traditional thinking up to now has been that the upright body form of modern humans has come about as a result of the ability to walk, and that running is simply a by-product of walking. Furthermore, humans have usually been regarded as poor runners compared to such animals as dogs, horses or antelopes. However, this is only true if we consider fast running over short distances. Even Olympic athlete can hardly run as fast as a horse can gallop, and can only keep up a top speed for fifteen seconds or so. Horses and antelopes, on the other hand, can run at top speed for several minutes, clearly outperforming us in this respect. But when it comes to long-distance running, humans do astonishingly well. They can maintain a steady pace for miles, and their overall speed compares favorably with that of horses or dogs.

Bramble and Lieberman examined twenty-six anatomical features found in humans. One of the most interesting of these is the nuchal ligament (颈背的韧带). When we run, it is this ligament that prevents our head from pitching back and forth or from side to side. Therefore, we are able to run with steady heads held high. The nuchal ligament is not found in any other surviving primates (灵长类动物), although the fossil (化石) record shows that Homo erectus, an early human species that walked upright, much as we do, also had one. Then there are our Achilles tendons (跟腱) at the backs of our legs, which have nothing to do with walking. When we run, these tendons behave like springs, helping to push us forward. Furthermore, we have low, wide shoulders, virtually disconnected from our skulls (the bony part of the head), another anatomical adaptation which allows us to run more efficiently.

But what evolutionary advantage is gained from being good long-distance runners? One assumption is that this ability may have permitted early humans to obtain food more effectively. “What these features and fossil facts appear to be telling us is that running evolved in order for our direct ancestors to compete with other carnivores (animals that eat meat) for access to the protein needed to grow the big brains that we enjoy today.” says Lieberman.

It’s often said that we human beings can dream in a foreign language. Could dreaming in a foreign language improve our memory? Does dreaming in a foreign language mean we are making progress in learning that language?

Before we look at multilingual (多语言) dreams, first we need to look at sleep. The connection between sleep and language can be applied to how we learn any language, including our native language. Even adults still learn about one new word every two days in their first language. But, if we are going to remember that new word better, what matters is that we need to connect it with what we have learned. And in order to do that, we “need to have some sleep”, says Gareth Gaskell, a professor at the University of York.

It’s during sleep that the integration (整合) of old and new knowledge happens. At might, one part of our brain — the hippocampus — takes whatever new information it receives during the day and passes it on to other parts of the brain to be stored. The role that dreams play in this night-time learning process is still being studied, but “it’s entirely possible that during multilingual dreams, the brain is trying to connect the two languages”, says Marc, a researcher at a university in Bern, Switzerland.

So having multilingual dreams could mean that our brain is trying to remember a new word or phrase. However, it could also have an emotional (情感) significance. Danuta, a professor of psycholinguistics at the University of Silesia in Poland, suggests that multilingual dreams can express “fears or wishes” around learning a foreign language, including the wish to be a local speaker or to be accepted within a certain community.

We clearly still have a lot to learn about multilingual dreams, but one thing seems certain: if you’re trying to learn a new language, you can sleep on it.

Over a million children have developed some form of intellectual （智力） disability over the past two decades after being exposed to chemicals including flame retardants, pesticides, lead, and mercury, a study has revealed.

The study focused on the four chemicals, which can be crossed from a mother to her unborn baby through the placenta（胎盘）and cause neurodevelopmental damage. The researchers looked at data from past studies, including blood samples taken from women of childbearing age and 5-year-olds.

Over the period, flame retardants, resulted in 738,860 cases of intellectual disability and an estimated 162 million lost IQ （智商）points, followed by lead at 330,684 cases, pesticides at 111,830, and mercury at 8,860. In recent years, pesticides and flame retardants have overtaken lead and mercury as the chemicals responsible for the biggest loss of IQ among children.

The researchers believe this is due to regulations cutting down the use of these chemicals. For instance, lead has been banned from gasoline, paint and drinking water systems in the U.S. and plants are not allowed to pump out mercury.

The researchers acknowledged limitations to their study, including that the exposure-response relationships might not relate to all populations. Positively, they found a huge drop in the estimated loss of IQ points among children.

Lead researcher Abigail Gaylord, commented: "Our findings suggest that our efforts to reduce exposure to heavy metals are paying off, but that harmful exposures in general continue to represent a terrible risk to people's physical, mental, and economic health. "Unfortunately, the minimal policies in place to remove pesticides and flame retardants are clearly not enough," she said.

She also added. Frequently opening windows to let persistent chemicals found in furniture   electronics, and carpeting escape, and eating certified organic produce can educe exposure to these harmful things"