The hypotheses in both target articles rely implicitly on much the same logic. For a “social-bonding” device to make sense, there must be an underlying reason why an otherwise-arbitrary behaviour sustains alliances – namely, credible signals of one's value to partners. To illustrate our points, we draw on the parallels with supposed bonding behaviours in nonhuman animals.

Attempts to understand the fundamental forces shaping conflict between attacking and defending groups can be hampered by a narrow focus on humans and reductionist, oversimplified modelling. Further progress depends on recognising the striking parallels in between-group conflict across the animal kingdom, harnessing the power of experimental tests in nonhuman species and modelling the eco-evolutionary feedbacks that drive attack and defence.

Tracheo-oesophageal prostheses are commonly inserted in patients following total laryngectomy to improve the quality of the voice. Unfortunately the device eventually fails and requires replacement. A valve change, although well tolerated by patients, necessitates an out-patient visit and delay in its replacement can lead to problems of pneumonia or dehydration. In this short paper we describe a simple temporary solution for a leaking valve and recommend its use in patients who are delayed in returning to the unit for example when on holiday.