Volume 658

Hiding from sight or using camouflage are excellent ways to try to avoid being caught while remaining still, but everything has to move at some point and evading predators while in motion is a trickier proposition. It has long been suggested that markings, such as a zebra’s stripes, can help to confuse would-be predators, but clear evidence for this is surprisingly lacking. In this week’s issue, Jolyon Troscianko and colleagues attempt to address this problem courtesy of butterflies. The team wanted to see if wing markings worked in combination with flight dynamics to help butterflies avoid being eaten by birds when in flight. The researchers approached the issue from multiple angles: first they filmed butterflies during take-off to capture their shape and wingbeat, finding that when combined with wing patterns, their apparent movement shifted backwards and sideways rather than forwards. They then did a phylogenetic analysis, which revealed this kind of effect is widespread among butterfly species. To verify this effect was a result of selection, they created a computer model for the evolution of wing patterns and found that it resulted in wing patterns similar to European butterfly species. Finally, they tested their ideas by having people try to catch virtual butterflies. As a result, the team affirmed that the combination of wing pattern and flight dynamics created an illusion of backwards motion that made it harder to apprehend the insects.

Some of the fundamental differences between humans and other apes lie in their skeletons. Evolutionary changes that shaped the human skeleton opened the way to key adaptations, such as walking upright on two legs and larger craniums that could accommodate bigger brains. But the genetic changes that gave rise to the human form are largely unknown. In this week’s issue, David Gokhman, Fumitaka Inoue and colleagues work to change that by mapping the gene-regulatory changes that helped drive the evolution of the human skeleton. Using cells found in cartilage called chondrocytes, the researchers generated a genome-wide atlas of human-specific changes in gene regulation and the genetic sequence variants that drive them. The researchers also shed light on the cost of the bipedal human skeleton: they found a marked suppression of glycosaminoglycan biosynthesis in humans, which could help to explain why humans are so susceptible to degenerative skeletal diseases.

Studying how the human brain develops and functions is challenging, not least because access to living human brain tissue is understandably limited. Human brain organoids, models generated from stem cells, have proved valuable in this respect by providing a way to study living neural cells. But these models still have limitations: they are typically not integrated with other brain structures and offer limited insight into circuit-level or behavioural consequences. In this week’s issue, Sergiu P. Pașca and colleagues present an experimental model designed to overcome some of these limitations. The researchers developed a genetic strategy to generate mice lacking most of the cerebral cortex and hippocampus, creating space into which they grafted a human cortical organoid, generating what they call a ‘xenocortical mouse’. The grafted organoids grew extensively, differentiated into a diverse range of human neural cell types and organized into neural circuits that integrated with the host brain. The researchers were also able to use the model to assess aspects of behaviour and examine the effects of neurological injury. The team suggests that this model could aid the study of human neurodevelopment, neurological and psychiatric disorders, and potentially therapeutic interventions. The work was conducted under extensive ethical oversight, and the team emphasizes the importance of developing appropriate guidance as the field considers the scientific, medical, social and ethical implications of such models.

The cover captures an aerial gathering of Natal long-fingered bats (Miniopterus natalensis). Bats are extraordinary creatures — they are the only mammal capable of powered flight, have remarkable disease resistance, use echolocation for navigation, hibernate and have longer than expected healthspans. But our knowledge of bat evolution and their remarkable adaptations is far from complete. In this week’s issue, Emma Teeling, Michael Hiller, Liliana Davalos, Sonja Vernes, David Ray and their Bat1K consortium colleagues present genomes for 103 bat species, representing all 21 bat families. Using these data, the researchers were able to redraw the bat phylogenetic tree, resolving some contested relationships among species as well as identifying the factors that originally caused the confusion. The team was also able to combine the genomic data with fossil data to probe the question of how long ago and where bats originated, estimating that they arose about 60 million to 65 million years ago in Europe.