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The sages: Zarathustra (left), Buddha, Confucius and Plato (right) were lone cultural innovators whose teachings eventually touched the entire globe, argued Jaspers.Credit: Getty/Alamy

The largest ever cross-cultural survey of historical and archaeological data casts doubt on the ‘Axial Age’ — a supposed time around the middle of the first millennium BC when humanity passed through a psychological watershed and became modern. Out went divine rulers and human sacrifice, in came social justice and the rule of law in what is now Greece, Israel–Palestine, Iran, India and China. An analysis of a huge global history database called Seshat found that humanity’s culture shift happened over a jumble of locations and times and not as a simultaneous shift. Critics say that the work — published as a non-peer-reviewed book — debunks a strict interpretation of the Axial Age idea that few still adhere to.

Nature | 6 min read

The Center for International Forestry Research (CIFOR) has withdrawn a report that suggested fires burnt more than 1.6 million hectares of land in the country during 2019, 40% more than the government's own calculations for the same period. The Indonesian government and local scientists had criticized the CIFOR analysis, saying that it relied on satellite data that hadn’t been confirmed with ground observations.

Nature | 3 min read

Researchers have embedded the instructions for making a 3D-printed bunny inside the object, using DNA to store the data. It’s a fun example of how DNA — capable of encoding huge amounts of data and robust enough to last for centuries — can be used to create materials with embedded memory. Scientists were able to replicate the bunny using the DNA instructions incorporated in its plastic, four times over.

New Scientist | 3 min read

Reference: Nature Biotechnology paper

Features & opinion

Epidemiologists have long been frustrated by observations that link environmental exposures and health. Mendelian randomization offers a simple way to detangle correlation from causation by relying on gene variants that mimic environmental factors. Do selenium supplements protect against prostate cancer, for example? Find men who are genetically predisposed to have high selenium levels and see whether they get less prostate cancer than others. The problem is, critics argue, that not all Mendelian randomization studies are sound.

Nature | 11 min read

For synthetic chemist Thomas Poulsen and his daughter Filucca, a playful chemical structure will forever be connected with her cancer diagnosis. Their moving story — which introduces Filucca as the youngest ever author in Nature Chemistry — is a reminder of the contributions of synthetic chemistry to medicine and the importance of play in scientific creativity.

Nature Chemistry | 7 min read

Twitter has become a place for scientists and academic physicians discuss research, raise their profiles and communicate across fields. Some institutions are even starting to consider social-media activity in hiring and promotion decisions. “You don’t hear much anymore that you’re wasting your time on Twitter and should be writing a paper,” says emergency physician Esther Choo.

Nature Medicine | 8 min read

Image of the week

Gerhard Wurm, Tobias Steinpilz, Jens Teiser and Felix Jungmann

Static electricity might play a part in helping the seeds of planets stick together. Scientists filled a box with tiny glass beads and used a catapult to shoot it to the top of a 120-metre-tower. Then they watched as the beads fell, in a simulation of microgravity. The beads gained electrical charge from static electricity and stuck together in clumps up to several centimetres across (there they are in the time-lapse image above). The finding offers a solution to the mystery of how the dust particles in protoplanetary disks adhere when they’re too small for gravity to bind them together. (New Scientist, 2 min read)

Reference: Nature Physics paper (Gerhard Wurm, Tobias Steinpilz, Jens Teiser and Felix Jungmann)