Evolution of the immune system and modern lifestyle have left us vulnerable to coronavirus – iNews

As we shelter behind closed doors, the Sars-CoV-2 virus causing Covid-19 has spread like no other disease before. In just a few months, from its identification in December 2019, more than a third of humanity was living under some form of lockdown. It is, to use the clich of 2020, unprecedented.

The Covid-19 pandemic has undeniably and dramatically exposed many weaknesses in human society. But it has also revealed that, despite the enormous advances we have made in medical science and technology, humans are just as vulnerable as any other organism to a novel disease. We are equipped with a very effective immune system that keeps us all alive, but that system has to learn to identify new invaders, and to react appropriately. Our naive immune system renders us all vulnerable to Covid-19, and in some people the overreaction of the immune system in response to the virus, a cytokine storm, can be fatal.

Our immune system, in all its complexity, is an evolved feature. It is an adaptation that, through natural selection, has been shaped and refined to combat disease. But there are subtler aspects of our evolutionary heritage at play during this pandemic. In the modern world of our own creation some of these aspects, so central to our global dominance as a species, can also conspire against us.

Evolution has equipped humans with large and complex brains capable of abstract thought, innovation, language and qualities we term intelligence. The evolved structure of our brain and the thought processes it allows also help us to be social, living and working collectively. Together, these features have allowed humans to achieve truly incredible things. At the same time, some of these features have rendered us horribly and uniquely vulnerable topandemics.

Social behaviour was essential during our evolutionary past, when our ancestors were far more likely to be the hunted than the hunter. Grouping for defence, and using the power of groups to keep safe and extend our diet, went hand-in-hand with evolutionary changes, and larger social units became possible. This accelerated greatly when we latched onto the idea of agriculture. Released to some extent from a foraging existence, human societies expanded, our skulls, dentition and metabolism evolved, technological advances flowed and ever larger settlements became possible. The supercity of the modern world is the culmination of this simultaneous expansion and concentration of humanity. Technology, arising from our unparalleled ability for innovation allows for such control over our environment that sometimes tens of millions of people are able to live a high-rise, high-density lifestyle, literally on top of each other. But high-density urban living provides the perfect conditions for a disease to spread.

The modern lifestyle hugely increases the number of people we have contact with, both socially and when we are crammed together in offices, streets and train carriages. Our social behaviour is now a threat, our conversations a liability. The primary defensive strategy in the face of Covid-19 is to actively and continually oppose our evolutionary heritage and, rather than group together for defence, we must defend ourselves by isolation.

Social distancing is affecting most parts of our daily lives at a local level, but we have also distanced globally. Our large and innovative brains dreamed of flight long before we invented the jet engine and shrank the world. The problem is that our ability to fly is also shared by any diseases we carry with us.

Gathering together people from far and wide for long periods in cramped airports and flying them all over the world is a wonderful dispersal mechanism for a virus like Sars-Cov-2. It is evolution that gave us all the innovative power of our brain, and it is our brain that has allowed us to create a globalised, interconnected world. If viruses had hands they would be have been rubbing them together in anticipatory glee when the Wright brothers took to the air.

Our cerebral evolutionary legacy laid the track for this pandemic but evolved aspects of our bodies arent always helping either. We have a wonderful ability to lay down fatty reserves, and for many of us the modern world is a landscape of caloric potency and opportunity.

Obesity is a major health risk any way you look at it, but it is also emerging as a risk factor for complications arising from Covid-19. The simple evolutionary story of obesity, often repeated, is that we are famine-adapted creatures living in a world of feast. The thrifty gene hypothesis as it is known is a seductive and popular idea, not least because of the implication that getting fat is somehow not our fault.

But it has proved difficult to support. Thrifty genes have been identified, in South Pacific islanders for example, but globally the evidence suggests that obesity cannot be put down to a Boy Scout metabolism, always prepared for famine.

Another evolutionary explanation is that, a few million years ago, the predation risk to our ancestors decreased. Evolved upper limits to fat storage were no longer so restrained by having to run away and they changed upwards not by natural selection but by a process called genetic drift (the drifty gene hypothesis). Whether we are thrifty or drifty, echoes of the mismatch between our evolutionary past and the calorie-filled modern world we have created are being heard.

Beneath our thin veneer of civilisation, far away from the dazzle and glare of our achievements, humans are vulnerable animals. Covid-19 has changed that. It has found itself the perfect host, a species with a powerful evolutionary double-hit of highly social behaviour and an innovative brain, leading to dense urban living and global travel.

The very nature of the modern world, building as it does on our evolutionary heritage, is our weakness in this pandemic. But just as our brain power helped us to get into this, it will also be our way out.

Unfit for Purpose: When Human Evolution Collides with the Modern World by Adam Hart (Bloomsbury Sigma, 16.99) is out now