The heartbeat of the city

Human activity is organised around daily and weekly cycles, which should, in turn, dominate all types of social interactions, such as transactions, communications, gatherings and so on. Yet, despite their strategic importance for policing and security, cyclical weekly patterns in crime and road incidents have been unexplored at the city and neighbourhood level. Here we construct a novel method to capture the weekly trace, or “heartbeat” of events and use geotagged data capturing the time and location of more than 200,000 violent crimes and nearly one million crashes in Mexico City. On aggregate, our findings show that the heartbeats of crime and crashes follow a similar pattern. We observe valleys during the night and peaks in the evening, where the intensity during a peak is 7.5 times the intensity of valleys in terms of crime and 12.3 times in terms of road accidents. Although distinct types of events, crimes and crashes reach their respective intensity peak on Friday night and valley on Tuesday morning, the result of a hyper-synchronised society. Next, heartbeats are computed for city neighbourhood ‘tiles’, a division of space within the city based on the distance to Metro and other public transport stations. We find that heartbeats are spatially heterogeneous with some diffusion, so that nearby tiles have similar heartbeats. Tiles are then clustered based on the shape of their heartbeat, e.g., tiles within groups suffer peaks and valleys of crime or crashes at similar times during the week. The clusters found are similar to those based on economic activities. This enables us to anticipate temporal traces of crime and crashes based on local amenities.

‘Tuesday Morning’, the schoolboy and Mann

The rediscovery of human remains, correspondence and other unpublished excavation archival material in the Glasgow Museums collection of Ludovic McLellan Mann prompted the reappraisal of a short archaeological investigation undertaken in April 1931 at Holm Park, near Ballantrae, Ayrshire, by a schoolboy, Eric French and his biology teacher, William Hoyland. This article offers a re-evaluation of their fieldwork which exposed two inhumation burials, named ‘Tuesday Morning’ and ‘Tuesday Afternoon’. Eight dog whelk shells remain from an overlying diffuse shell midden spread that may reflect the remnants of a dye-processing site. The skeletons and marine shells went on temporary display at Bryanston School, Dorset. The area south of Ballantrae is well known for prehistoric flint scatter sites and the finds presented the intriguing possibility that the burials might be Mesolithic in age, the excavators believing they might even be Palaeolithic. A collection of flint cores, initially associated with the archive, now appears unrelated to this excavation for it was found with a note written by a local lithic collector, William Edgar. New osteological analysis confirmed the presence of at least two adult individuals, and one bone sample returned an early medieval radiocarbon date. This evidence contributes to national understandings of early historic burial practices in unenclosed cemeteries during the transition from Iron Age pagan to Christian burial rites, important given the paucity of 1st millennium evidence in south-west Scotland. It also offers insight into an earlier account of multiple inhumation burials, found in the general vicinity in 1879, although aspects of the precise location and relationship between the two discoveries is currently unresolved. Mann’s correspondence with French’s father, a prominent Glasgow industrialist, and with Hoyland reveals the character of archaeological social networks in western Scotland during the 1930s which have been a neglected aspect of research to date. Canmore ID 60957 Canmore ID 60935 Canmore ID 275902