A ladybird larva is on the prowl on a witch hazel plant. The youngster is a voracious predator and it’s hunting for aphids. It seems to have found a bountiful feast – a swollen structure called a gall that houses an entire aphid colony. With so many meals in one place, the colony seems easy prey, but it has staunch defenders.
As the ladybird approaches, aphids pour out of the gall and grab the predator by their jaws and legs. It’s a suicide defence. The aphids secrete massive amounts of waxy liquid from their bodies, which quickly solidifies and glues the ladybird to the plant. Unable to walk or bite, the ladybird dies and the aphids go with it. In the video below, you can see what happens when one of these aphids is prodded with a needle.
There is more to these suicidal protectors that meets the eye. Keigo Uematsu and University of Tokyo found that all of them are ‘menopausal’. They are the parents of the other aphids in the gall but their reproductive days are long behind them. With no further opportunities to raise the next generation, their final role is to defend their offspring, with their lives if necessary.
Imagine that a massive hole appeared in a wall of your house, and you’d decided to fix it yourself. You head over to a DIY store and load up on plaster, tools and paint and look forward to many hard and tedious hours of work. If that seems like a chore, you might get some perspective by considering the plight of the gall aphid Nipponaphis monzeni. When holes appear in their homes, some unlucky individuals are tasked with repairing the damage using their own bodily fluids. They sacrifice themselves for the sake of some DIY.
Some species of aphids are heading towards the incredibly cooperative lifestyles of social insects like ants, bees and termites. They live in large hollow growths called galls, that sprout from the very plants whose sap they suck. The galls provide them with protection from predators, shelter from the elements and constant food. They are a precious resource indeed, and every colony of social aphids have a special caste of sterile individuals whose job it is to defend the gall and attack intruders. These are the soldiers.
But in a few species, such as N.monzeni, soldiers have a truly bizarre part-time job- they are suicide-plasterers. When their homes are breached, the soldiers leach their own bodily fluids onto the wounded area, mix it with their legs and plaster it over the hole. The liquids soon harden and within an hour, the gap has been plugged at the cost of the soldiers’ lives.
The aphids’ gall-repairing antics are remarkably similar to what happens when animals develop cuts and wounds. The fluid around the area clots and hardens to form a scab. This provides a temporary seal, that gives the surrounding cells enough time to grow, divide and restore the broken tissues. The exact same thing happens to the gall – the only difference is that its clots and scabs are provided not by the plant, but by the aphids it houses.
The trauma of child abuse can last a lifetime, leading to a higher risk of anxiety, depression and suicide further down the line. This link seems obvious, but a group of Canadian scientists have found that it has a genetic basis.
By studying the brains of suicide victims, Patrick McGowan from the Douglas Mental Health University Institute, found that child abuse modifies a gene called NR3C1 that affects a person’s ability to deal with stress. The changes it wrought were “epigenetic”, meaning that the gene’s DNA sequence wasn’t altered but it’s structure was modified to make it less active. These types of changes are very long-lasting, which strongly suggests that the trauma of child abuse could be permanently inscribed onto a person’s genes.
Child abuse, from neglect to physical abuse, affects the workings of an important group of organs called the “hypothalamic-pituitary-adrenal axis” or HPA. This trinity consists of the hypothalamus, a funnel-shaped part of the brain; the pituitary gland, which sits beneath it; and the adrenal glands, which sit above the kidneys. All three organs secrete hormones. Through these chemicals, the HPA axis controls our reactions to stressful situations, triggering a number of physiological changes that prime our bodies for action.
The NR3C1 gene is part of this system. It produces a protein called the glucocorticoid receptor, which sticks to cortisol, the so-called “stress hormone”. Cortisol is produced by the adrenal glands in response to stress, and when it latches on to its receptor, it triggers a chain reaction that deactivates the HPA axis. In this way, our body automatically limits its own response to stressful situations.
Without enough glucocorticoid receptors, this self-control goes awry, which means that the HPA is active in normal situations, as well as stressful ones. No surprise then, that some scientists have found a link between low levels of this receptor and schizophrenia, mood disorders and suicide. So, childhood trauma alters the way the body reacts to stress, which affects a person’s risk of suicide or mental disorders later in life. Now, McGowan’s group have revealed part of the genetic (well, epigenetic) basis behind this link.
When it comes to discussing suicide bombers, the controversial topic of religion is never far behind. Scholars and pundits have proposed several theories to explain why people would sacrifice their lives to take those of others, and conjectures about religious views seem easy to defend. After all, anthropologist Scott Atran estimated that since 2000, 70% of suicide attacks have been carried out by religious groups, and Islamic ones in particular.
But for all the speculation, very few people have examined the supposed link between religion and suicide attacks with an objective scientific eye. Enter Jeremy Ginges from the New School for Social Research in New York. He has used four related studies to show that there is indeed a link between religion and support for suicide attacks, but it’s a complicated one.
Ginges studied a wide variety of religious people from various cultures and faiths – from Palestinian Muslims to Israeli Jews, and from British Protestants to Indian Hindus. Across the board, Ginges found that a person’s stance on martyrdom had little to do with their religious devotion or to any particular religious belief. Instead, it was the collective side of religion that affected their stance – those who frequently took part in religious rituals and services, were most likely to support martyrdom.
Various commentators have suggested that religious devotion makes it easier for people to buy into the ethos of suicide attacks because some religious beliefs denigrate those of other faiths, promise rewards in the afterlife or glorify the notion of martyrdom. According to Ginges, the advocates of this idea, Richard Dawkins among them, tend to bias their attention towards the more violent aspects of religious traditions or texts, in a fairly simplistic way.
An alternative idea says that the social side of religion is the more powerful influence. During religious rituals such as church or mosque services, large groups of people move or speak as one, invoking a powerful sense of shared identity. By strengthening bonds within a group, these rituals can augment a person’s loyalty to that community, often to the exclusion of those outside it. Suicide attacks, which sacrifice a person’s life for the sake of the collective cause, could be viewed as the extreme dark side of this cliquey behaviour.
Ginges, together with Ian Hansen and Ara Norenzayan, carried out four studies to distinguish between these two theories and they’ve consistently found support for the latter, across a variety of religions.