Volume 651

The cover shows an artist’s impression of a human and their canine companion near a settlement in Ice Age Switzerland. Dogs have been companions for humans for millennia. They were the first animal to be domesticated, and remains with possible dog morphology have been dated to at least 14,000 years ago. But the exact origins and nature of early dogs remain a mystery. Two papers in this week’s issue go some way to resolving this problem. In one, Anders Bergström, Pontus Skoglund and colleagues analyse the genomes of some 200 ancient dog and wolf remains, while in the other, William Marsh, Lachie Scarsbrook, Laurent Frantz and colleagues report the genome sequences of two dogs dating back to 14,000–16,000 years ago — the earliest dogs to be sequenced. Together, the papers show that dogs were widely distributed across western Eurasia long before the introduction of agriculture. They also find evidence that the genetic diversification of dogs started much earlier than had previously been thought.

The cover shows the moth Idalus iragorri, one of many insect species found at low to medium elevations in the eastern Andes. More than 70% of all insect species are found in the tropics, but the potential effects of global warming on these key components of the ecosystem are not well understood. In this week’s issue, Kim Holzmann and colleagues aim to resolve this with an analysis of around 2,300 insect species from Africa and South America. They found that insects at high elevations were better able to adapt to higher temperatures, but at lower levels they were not. Overall, the team found that insects in the tropics have a limited capacity to cope with global warming — half the lowland insects that were studied are at risk of dying as a result of projected higher temperatures.

Superluminous supernovae are at least ten times brighter than their regular counterparts, but astronomers have remained in the dark about what exactly powers these phenomena. In this week’s issue, Joseph Farah and colleagues confirm that magnetars — highly magnetized neutron stars formed by a supernova — are a driving force of these explosions. The researchers analysed light emitted by a superluminous supernova more than a billion light years from Earth. Using a new model of the supernova, they determined that a rapidly rotating magnetar is at the centre of the explosion, and that the massive amounts of energy deposited into the supernova ejecta is the cause of the superluminous glow. A disk of accreting matter spins around the magnetar (as pictured on the cover) and this disk ‘wobbles’ owing to an effect predicted by Einstein’s general theory of relativity. This results in the amount of energy being deposited fluctuating, accounting for the unique rise and fall in the supernova’s brightness observed from Earth.

Bony fish account for some 98% of all vertebrate species, but the early stages of their evolution are not well understood. The core issue is the fragmented fossil record for specimens that date back earlier than the start of the Devonian Period some 419 million years ago. Across two papers in this week’s issue, Min Zhu and colleagues help to plug that gap. In the first paper, the researchers reveal the near-complete skeleton of a small bony fish dating to the early Silurian (around 436 million years ago), making it the oldest known bony fish. Named Eosteus chongqingensis, this 3-centimetre fish displays features that place it close to the earliest stages of bony fish evolution. In the second paper, the researchers reveal fossil material from the fish Megamastax amblyodus, the largest pre-Devonian vertebrate currently known. Dated to around 423 million years ago, these latest remains add an entire skull with teeth and jaws to the picture, offering fresh insight into the origin of bony fish characteristics. Both Eosteus (middle) and Megamastax are pictured in the artist’s digital model on the cover.