Science News
Headlines

. Early humans left Africa and reached Asia earlier than thought
. New mathematical geometric shape discovered
. A search for proof that the Maya tracked comets
. Procrastination may hurt your health
. Researchers have mapped every nerve cell in the larval fruit fly brain 
. Hand dryers can infect clean hands with bathroom germs
For more details on some of these topics, read on.

. Early human left Africa and reached Asia earlier than thought
Fossils and other evidence have proved that humans originated in Africa.  But we still do not know when exactly our earliest ancestors left Africa and how they spread around the world.
Recently two fossils were found in a cave in northern Laos (in South east Asia). The two Laos fossils — a fragment of a leg bone and part of the front of a skull — were found in Tam Pa Ling cave. The archaeological site was discovered in 2009 when another partial skull was unearthed.
In addition to the latest finds, two jawbones, a rib and a phalanx have also been discovered at the site, and the physical features of the remains all suggested they belonged to early modern humans.
Dating fossils from the site proved tricky. They were too old for radiocarbon dating, which can only date remains that are less than 46,000 years old.  Also, the human fossils found at the site are protected by Laotian heritage laws that prevent any kind of destructive analysis. Instead, the team involved in the study used two different techniques to estimate the fossils’ age.
All sediments and soils contain small amounts of radioactive elements such as potassium, uranium, thorium, and rubidium. These slowly decay over time by emitting radiation. This radiation they produce is absorbed by mineral grains in sediments such as quartz and potassium feldspar. The radiation causes electric charge to accumumate in these underground sediments in what are called "electron traps". The amount of charge trapped depends on the amount of radiation at the location. When these sediments are taken out and exposed to either light or heat, they exhibit luminescence (they glow) as the trapped energy is released. The amount of energy released indicates how long it has been buried, that is, the age of the layer.  The scientists used this technique and another technique called electron-spin-resonance dating to find the age of these fossil remains.
The two fossils were estimated to be 68,000 to 86,000 years old, with the leg bone fragment being the older find. DNA analysis of present-day human populations indicates that early modern humans left Africa around 50,000 to 60,000 years ago. It is believed that these early humans left Africa, followed the coastlines and islands of southeast Asia to reach Australia. But these fossils indicate that there were early human settlers in Laos much earlier. It also challenges the belief that these migrations took place along the coast, as Laos is not only inland (see map) but also mountainous and forested.
At a nearby site, known as Cobra Cave, a tooth believed to belong to a Denisovan, an elusive early human, has been found. However, that tooth is 70,000 years older than the earliest Tam Pa Ling remains, so there’s no evidence the two species of human mixed or coexisted at the site.
The team expects to unearth more human fossils from the region.  Sites like Tam Pà Ling where there is a continuous, undisturbed stratigraphy (layers of sediment) that holds multiple fossils over a long period of time will teach us a lot about past migrations and how early modern humans and other hominins changed over time.

. New mathematical geometric shape discovered
A tessellation or tiling is the covering of a surface, using one or more geometric shapes, called tiles, with no overlaps and no gaps. For instance, you may have rectangular tiles on the floor in your room. All the tiles are the same shape and you can lay them side by side to cover the entire floor without any gaps. Even if the surface becomes infinitely bigger you can still tile it completely. If you look at a small portion of the surface, it looks like any other portion of the surface since the tiles are identical and the pattern repeats. Square, rectangular, triangular and even hexagonal shapes can be used for such tiling.

Most tessellations that have been found are symmetric geometric shapes that repeat. For many years, mathematicians have been searching for a geometric shape that can cover a surface without gaps, but forming a pattern that doesn't repeat. In fact, it was not even clear that such a shape exists.
Recently, in March this year, D. Smith, J.S. Myers, C.S. Kaplan and C. Goodman-Strauss found a 13-sided tile that can do this. It looks like a hat or T-shirt and a small part of the pattern is shown in the figure. Such a tile is called an einstein. If you cannot see the hat or T-shirt, look at the coloured picture with coloured T-shirts and grey hats!
The name “einstein” doesn’t refer to the famous physicist, Albert Einstein. In German, ein Stein means “one stone.” That refers to using a single tile shape to cover the surface.  The tiles fit neatly together and can cover an infinite plane. But they are aperiodic. That means the hat can’t form a pattern that repeats.  David Smith identified the hat. He does math as a hobby, not as his job.  He describes himself as an “imaginative tinkerer of shapes.” He was part of a team of researchers that reported the hat in a recent paper.
The hat is a polygon shape with straight edges and looks surprisingly simple.  Mathematicians previously knew of tilings that couldn’t repeat. But all used two shapes or more. “It was natural to wonder, could there be a single tile that does this?” 
The hat einstein made a pattern that involved using both the tile and its mirror image. If you look for a while, you will realise that the "hat" and the "T-shirt" are mirror reflections of each other. 
Recently, yet another tile was found. It also makes a pattern that never repeats, but the surface can be tiled with just this shape, without using its reflection (see figure). This shape, called a spectre, covers an infinite plane with some of them a light green connected to a dark green scattered amongst white spectres.  Although certain clustered arrangements of the tiles can reappear, the entire pattern doesn’t repeat indefinitely, as a chess-board pattern does, for example. These discoveries have led to a new understanding of geometric shapes and their properties.

. A search for proof that the Maya tracked comets
The Mayan civilisation existed in central America and modern day Mexico. The first Maya cities developed around 750 BC, and flourished till about 300 years ago. It is known by its ancient temples and glyphs. Its Maya script is the most sophisticated and highly developed writing system of those times. It is also famous for its art, architecture (beautiful temples), mathematics, its calendar, and its astronomical system.
The Maya were famous for their astronomy in particular. They noted observations of celestial bodies, including the movements of the Sun, Moon, Venus, and the stars. Apart from its use in astrology, it was also used to help decide when to plant crops and harvest them.
They also recorded eclipses of the Sun and Moon; these were compared with events in the past, and they used this to predict that similar events would occur in the future as well. They had made such a systematic study that they even had tables of eclipses and a sophisticated calendar system.  In fact, their astronomical knowledge was more accurate at that time than comparable knowledge in Europe.
One interesting fact was the measurement of the length of the cycle of Venus. You know that the moon has phases: it goes from full moon to new moon back to full moon in about 29.5 days. If you observe carefully, Venus also has phases, just like our Moon – full, half, quarter, etc. The complete cycle, however, new to full and back, takes 584 days.  The Maya measured this 584-day Venus cycle with an error of just two hours! All this with observations by the naked eye! If you observe 5 cycles of Venus, that equals 5x584=2920 days. But 8 Earth years also equals the same: 8x365=2920! The Maya noticed and recorded this as well. 
But a question that has puzzled historians for a long time was whether the Mayans recorded comets and supernovas. Comparing dates of known historic novas and comets with Mayan dates, a researcher found no acceptable correlation. Nevertheless, it is believed that the Mayas probably did record such events and that a record will eventually be found.
Recent research shows that several early codexes (ancient manuscripts) and stones may have recorded hieroglyphs that together mean “comet.” But wars with Spanish invaders destroyed many of the originals, and only copies which were made well after the Maya empire’s collapse are now available. However, these records clearly depict comets.
In 2017, an analysis of Maya records and astronomical data hinted that the Maya indirectly marked at least one comet by predicting when meteor showers would dazzle the sky. Between the years 250 and 909 CE, six royal coronations happened within days of the annual Eta Aquariid meteor shower, which occurs when Earth passes through the tail of Halley’s comet. The picture shows several pages of what is called the Dresden codex. It is believed to be the oldest surviving book written in the Americas, dating to the 11th or 12th century and is written in Maya hieroglyphics. It may even be older by about a century. The codex was rediscovered in the city of Dresden, Germany, hence the book's present name. The codex is 78 pages long and contains information relating to astronomical and astrological tables, religious references, seasons of the earth, and illness and medicine. It also includes information about conjunctions of planets and moons. Given their long and scientific civilisation, it is very likely that the Mayas did know about the paths of comets and hopefully one day such records will be found.

. Procrastination may hurt your health
Procrastination is “putting off to later what you know you should be doing now” — even if you’ll be worse off, says Piers Steel. He’s a psychologist at the University of Calgary in Canada.
In a study that studied thousands of university students, scientists linked procrastination to a wide range of poor outcomes. They included depression, anxiety and even disabling arm pain.  The study is one of the largest yet to tackle procrastination’s ties to health. The new study could raise awareness of the physical health consequences of procrastination.” This study was observational. That means scientists measured the outcomes but didn’t test the impacts of any specific factor.  
Whether procrastination harms health can seem like a chicken-and-egg question. Does procrastinating lead to health problems? Or do certain health problems make people more likely to put things off? These can be hard to tell apart, Johansson says. (Plus, it may be a bit of both.) And controlled experiments on procrastination aren’t easy to do. You can’t just tell a study participant to start procrastinating and wait to see if their health changes, he explains.
Many past studies have used self-reported surveys from a single point in time. But just one snapshot of someone makes it tricky to untangle cause and effect. The new study, though, followed about 2,500 students over nine months. That was enough time to track whether procrastinators later developed health issues.
About one in every five adults is thought to be a chronic procrastinator. Everyone might put off a task now and then. But chronic dawdlers make it their lifestyle.  On average, dawdlers tended to fare worse over time than did peers who were more prompt. For instance, the dawdlers were slightly more stressed, anxious, depressed and sleep-deprived. They had a greater risk of developing both physical and psychological problems later on.
Stress may be at least partly to blame. And ill effects of chronic dawdling could build up over time, Sirois says. Procrastination alone may not cause disease, she notes. It could be, however, “one extra factor that can tip the scales.” 
No, procrastinators are not lazy.  Many procrastinators may think they perform better under pressure. But Ferrari has reported the opposite. They actually worked more slowly and made more errors than non-procrastinators, his data show. (Some people with ADHD or similar conditions, however, report finding some procrastination helpful for focusing on tasks.) And when deadlines are less fixed? Procrastinators tend to let their work slide.
For years, researchers have focused on the personalities of people who put things off. Findings vary, but some scientists suggest procrastinators may be impulsive. They may be worriers and have trouble regulating their emotions. One thing procrastinators are not, Ferrari emphasizes, is lazy. They’re actually “very busy doing other things than what they’re supposed to be doing,” he says.
When people put off a tough task, they feel good — in the moment.  Procrastinating is a way to sidestep the negative emotions linked to the task. We’re hardwired to avoid anything painful or difficult. When you procrastinate, you get immediate relief. Stress can strain people’s ability to cope. That makes it even more appealing to put off hard things. But the relief it provides is only temporary.  Rozental says most research today suggests procrastination is a pattern of behavior. And if it’s a behavior, he adds, that means it’s something you can change, whether you’re impulsive or not.  
So how can people seek out ways to stop dawdling? Researchers have tried a whole range of treatments — and it’s not clear which works best.  Hard-core procrastinators may benefit from what’s called cognitive behavioral therapy. This involves managing thoughts and emotions and trying to change behavior. But not many studies have examined such treatments. More work in this area would help.

Sources:
https://edition.cnn.com, https://www.sciencenews.org,
https://www.snexplores.org