In the early hours of yesterday morning, Essex police were called to a parked lorry container. Inside were the bodies of 39 people, one of them a teenager. Their identities and nationalities were initially unknown, but we have since learned that they are Chinese nationals. The driver, a young man from Northern Ireland, has been arrested.

Normally, faced with such a body count and the appearance of mass murder, politicians and commentators would be circumspect, perhaps uttering routine expressions of horror and pledging their support to a police investigation. But they would not have already worked out who was to blame. Still less would they announce their theories in the House of Commons. During Prime Minister’s Questions on the day of the discovery, the Thurrock MP, Jackie Doyle-Price, said: ‘To put 39 people into a locked metal container shows a contempt for human life that is evil. The best thing we can do in memory of those victims is to find the perpetrators and bring them to justice.’ Boris Johnson was quick to respond: ‘All such traders in human beings should be hunted down and brought to justice.’

Anthony Steen, a former Tory MP and the chair of the Human Trafficking Foundation, was more expansive in his speculations on BBC Radio 5, suggesting to Rachel Burden that the people were probably fleeing persecution in their countries of origin, and that those countries may well have been Afghanistan, Syria and Iran. That assumption, though mistaken, was not an unreasonable one. Steen seemed to be about to broach the broader questions of exclusion, to explain why people would pay smugglers tens of thousands of pounds rather than, say, hopping on a flight to Heathrow from Tehran, but at that point Burden closed things down: ‘A whole other debate,’ she said. A pity.

We may never know the stories of the people who asphyxiated in that container, just as we don’t know who thousands of the drowned in the Mediterranean are, or the names of the numberless dead whose desiccated corpses lie in the Arizona desert. But we do know that some of them were escaping the kind of persecution that would entitle them to sanctuary elsewhere under the 1951 Refugee Convention, and that others, their lives made intolerable by crime, or their opportunities curtailed by environmental degradation or malfunctioning economies, felt they had no choice but to seek a better life.

That things are going so badly for people that they have to leave friends and family should be a reason for human sympathy whatever the cause, but tracing those causes often leads straight back to those of us who live in the countries they are heading for, the decisions of our politicians and our ways of life. These explanations will not form part of the investigations by the Essex police. The countries mentioned by Steen are marked by our interventions, sometimes directly, sometimes through sanctions, sometimes through actions in the wider region such as the 2003 Iraq invasion. The environmental changes that are pushing many people to move are caused by greenhouse gases that they did not emit. The rich world’s appetite for narcotics, and the decisions of our leaders to fight a ‘war’ against them, lie behind the criminal violence that drives people from Central America and elsewhere.

China, where the victims found in Essex appear to have come from, is both a valued trading partner for the West and, for some minorities, a tyranny; a land of stunning wealth for some, of poverty and marginalisation for others. It is also a country with a global diaspora, but historic patterns of migration and family relationships have been blocked by the hardening of the world’s borders.

Those hard borders mean than people now have to pay smugglers to take them by dangerous methods and routes. The countries they are heading for, which never cease to trumpet how welcoming they are to ‘genuine’ refugees, are absolutely determined to prevent people who might claim asylum from arriving. A variety of measures, documented by David Scott Fitzgerald in Refuge Beyond Reach: How Rich Democracies Repel Asylum Seekers, now make it impossible for people with the wrong passport or the wrong profile to get on a plane from Tehran, Addis Ababa or Shanghai. They won’t be allowed to buy a ticket; airlines and shipping companies will stop them boarding without a visa, and no wealthy country will grant one. Countries along the way, often brutal dictatorships, are bribed to prevent the undesirable from crossing. Keep them there, out of sight: anywhere but here.

Johnson’s revulsion at ‘traders in human beings’ suggests an uncharacteristic aversion to entrepreneurship. But the rhetorical attempt to appeal to our sense that lives should not be bought and sold masks the fact that states also criminalise people who assist migrants and refugees out of solidarity and concern: the Sea Watch captains Carola Rackete and Pia Klemp were arrested by Italy for rescuing people in the Mediterranean; Scott Warren was prosecuted for providing aid in the Arizona desert; Cédric Herrou, a French farmer, was brought to trial for giving shelter to Africans freezing in the Alps. What our politicians and pundits object to is not the making of money from human suffering, or dead bodies, so long as the bodies are somewhere else. When they turn up in Essex, dead people are an embarrassment and the perpetrators must be found.