Ceva consultant
All around the world, politicians are struggling to achieve a balance between protecting their citizens’ health and enabling them to interact with each other in social and business settings. To help them decide on the relative merits of savings lives and safeguarding health systems through limiting social contact and opening up the economy to protect jobs and livelihoods, politicians are guided to vary extents by expert scientific and medical advice.
A recent review by Valéria Romano and colleagues from France and Japan, published in the journal Trends in Ecology & Evolution[1], provides a refreshing, new perspective. It considers how social animals – from ants to apes – handle the trade-off between socialising, such as sharing information about a good food source or mutual grooming, and avoiding the spread of infectious diseases between group members.
The authors point out that Shakespeare was aware of this trade-off several hundred years ago. In Henry IV, part 2, written in the late 1590s, he wrote: “It is certain that either wise bearing or ignorant carriage is caught, as men take diseases, one of another: therefore, let men take heed of their company.”
But they go on to explain that the natural world has vastly more experience in this field than humankind:
Our modern understanding of pathogen spread and its mitigation has a history of less than two centuries, whereas evolution has used hundreds of millions of years to hone solutions to this crucial challenge in nature.
The review explains that a wide range of defences have evolved to prevent or respond to infection with pathogens amongst social animals. In addition to immunological responses, some animals also exhibit behaviours including hygiene and self-medication, but they suggest social avoidance measures are probably the most important.
These range from infected individuals self-isolating, perhaps because the disease causes lethargy which naturally limits their ability to interact, to uninfected individuals recognising and avoiding infected group members, and even enforcement of isolation with infected individuals driven from the group.
Examples are cited for a wide range of species:
A small species of fish from Trinidad was observed to avoid individuals infected with a parasite.
Exposed to pathogens while foraging self-isolate while healthy ants decrease the time they spend with the rest of the colony.
A type of baboon, avoided grooming affected body parts of troop members infected with parasites.
Focusing on the role of individuals, as they navigate their social worlds and contribute to the various flows within their respective networks, highlights that effective epidemic control strategies depend on the collective sums of their behavior. We have shown that solutions do exist in social animals, and that, as in humans, other species can adapt their contact rates, their communication modalities, and their network structure to limit pathogen spread.
Just like the 1918 influenza pandemic, pending the introduction of an effective vaccine, the main tool being used to control the current pandemic is social distancing. This paper provides a timely reminder that the same strategy has been used in diverse species in nature from long before humans evolved.
1 Trends in Ecology & Evolution, October 2020, Vol. 35, No. 10 https://www.cell.com/action/showPdf?pii=S0169-5347%2820%2930184-1
