The ten plagues from a scientific angle

When we are injured and bleed, some of us may feel intense fear, sometimes physical weakness, and even faint in extreme cases, even if they are very minor injuries, where blood loss does not endanger us, or just a few drops in a blood test. The phenomenon is called “while bleeding” and about 4-3 percent of the population suffers from it.

Unlike other phobias, the reaction in a blood clot occurs in two stages: First, an anxiety response is typical as in many other anxieties. Next comes a second reaction of a sudden drop in heart rate and blood pressure characterized by dizziness and even a tendency to faint. This is due to the activation of the vagus nerve (stray nerve) typical of resting states.

It is not clear what the cause of the phenomenon is but there are several hypotheses. One hypothesis holds that this is an evolutionary instinct, as part of the “fight or flight” survival response that is characteristic of situations of danger and is sometimes also characterized by freezing in place as a kind of pretending to be dead. If we are bleeding there is probably something that caused it and it still endangers us so it makes sense in such a reaction. Another hypothesis is actually related to the prevention of blood loss. If we are bleeding, we want to lower our blood pressure to reduce blood flow from the wound and “gain time” until the clotting mechanism closes it.

In 1935, researchers in Australia made a serious mistake. Their intention was good: the sugar cane plantations in the north of the continent suffered badly from the damage of a local beetle, and they thought they had a perfect solution to the problem. In Puerto Rico, which suffered from a similar problem, reed toads (Rhinella marina) were released from America to prey on the beetles – and it seemed to work. Therefore, researchers also brought the toad to the state of Queensland in Australia, and by 1936 tens of thousands of toads were released there. 85 years later there are millions of such toads in Australia: they have been of almost no use against the beetles, but have caused severe damage to the local wildlife.

In Australia, toads had very few predators that threatened them and plenty of food. They multiplied rapidly, but the beetles were not really bothered: the beetles tend to live on the top edge of the sugar cane, and the toads do not climb well. In their place they ate other insects, and also food intended for domestic animals. Some local animals, mainly lizards and snakes, have tried to eat them, but reed toads are highly toxic, and have already caused a sharp decline in the numbers of some predators. Domestic dogs also suffer from this: Veterinarians in Australia report many cases of dog poisoning trying to bite the toads. It has recently been revealed that at least one predator, the water rat, has learned how to kill and eat the toads without being poisoned. Maybe this will be the solution against the toad plague?

Human lice as an oil are, unique to man. In the third plague it is written that both man and beast were harmed by the plague of lice, so it is likely that these are fleas, not insects that are today called lice.

Like fleas, human lice are blood-sucking external parasitic insects, but unlike many other fleas and insects, they are unable to jump or fly. They are highly contagious and pass on contact. In the case of head lice (Pediculus humanus capitis) the contact is head to head, and in the case of pubic lice (Pthirus pubis) the contact is between other parts of the body. It is possible to be infected with head lice and pubic lice through bedding, towels or hats, but this is extremely rare.

In contrast, the body lice (Pediculus humanus humanus) live mainly in clothing, can be infected through bedding and can also transmit diseases, such as typhus. It is especially common in conditions of overcrowding, poverty and lack of hygiene. Body lice can even be infected with Yersinia pestis, the bacterium that causes it, and studies have shown that they can also transmit the disease – at least to rabbits. Despite all this, the main “danger” to prepare is itching, as a result of a mild allergic reaction.

So where did the lice come from? Our head and body lice are related to chimpanzee lice. Evolutionary studies show that we were not infected with chimpanzees, but that even our common father and theirs had lice, when our lineages split, about six million years ago, the lice lineages also separated. Body lice split from head lice about 107,000 years ago, when humans began to wear clothing. In contrast, we got pubic lice from gorillas, somewhere about three million years ago. We were not asked how it happened.

This is the most mysterious of the ten plagues: it is not clear what, in fact, is that “guarantee.” The common interpretation is that these are predators of various species, but some also interpret the word as a swarm of flies or other insects. If these are predators, who are the animals you really would not want to see on your doorstep?

The largest predators in the world are toothed whales, but they live in the sea, and will have a bit of a hard time jumping in to visit. The largest terrestrial predator is the polar bear: the male can weigh up to 600 kilograms. Their relatives, the grizzly bears, are slightly smaller than them, but still among the largest. Following them in line is the Bengal tiger, which can reach a weight of 300 kilograms.

In the past, even larger predators lived on the ground. The Tyrannosaurus rex weighed between five and a half and eight tons, and its relative, Spinosaurus aegyptiacus, was even larger than it. In later periods, Arctotherium bears weighing over a thousand kilograms or more roamed South America, and Simbakubwa from Africa, belonging to a long-extinct family, weighed even more.

But size is not everything. Researchers have examined and found that of all the terrestrial predators, the strongest bite is actually not the property of these giants. The sea crocodile (Crocodylus porosus) holds the record, as long as we are willing to call it “terrestrial”. Next in line are the Jaguar and the Spotted Hyena, who use their powerful jaws to crack bones.

The biblical plague has affected animals and farm animals, but it is probably not the deadly thing we are familiar with. The disease is caused by a bacterium called Yersinia pestis and is the black plague that killed between a quarter and a third of the population of Europe in the 13th century and some studies claim that it killed about half of the Byzantine population. The main carriers of the bacterium are fleas that feed on the blood of rodents. Thus the disease easily spread over convoys of merchants moving from Asia to Europe and left many dead behind.

In its respiratory version this is highly contagious to humans and causes severe pneumonia. Today the disease can be treated with antibiotic treatment which makes it much less dangerous. Occasionally outbreaks are reported mainly in third world countries but it is very unlikely that this disease will develop into a widespread epidemic as in the past.

One of the earliest uses of biological weapons was in the disease, when Mongolian soldiers threw the bodies of soldiers who had died of the disease into the city of Kappa on the Crimean peninsula (now in Ukraine) during the siege of it in 1346.

The boils mentioned in the Bible are probably not a specific disease, but a general term for a wide variety of diseases that are expressed in wounds or skin lesions. One of them is probably a skin rash, which may be the result of an allergic reaction, for example to lice or fleas that have roamed in previous blows. In an allergic attack, the immune system of sensitive people tends to develop a reaction against “allergens” – foreign factors that are not dangerous in themselves, such as pollen, house dust mite secretions, eggs, peanuts, and more. Due to the large amount of allergens in the air, the allergic reaction is especially common in the spring, the Passover period.

The allergic reaction involves “mast cells” of the immune system. One of the types of antibodies that the body produces against the allergens also binds to the mast cells and causes them to secrete some substances that soak up the allergic reaction.

One of these substances is histamine, which increases the permeability of blood vessels and causes them to release fluid into the tissues, so for example swelling is seen in the area of ​​bites. Histamine also binds to receptors on skin nerve cells, which causes an itchy feeling. Following the secretion of these substances, the airways also constrict and fill with phlegm, which in turn causes coughs and sneezes, and increased intestinal activity.

The collection of all these events is the allergic reaction, which can range from a feeling of itching in the skin and irritation in the nose to death following anaphylactic shock – an excessive allergic reaction that manifests itself in a drop in blood pressure, a particularly fast heart rate and an increased respiratory rate.

The hail starts as a drop, and sometimes a snowflake, but instead of falling down and reaching the ground, strong vertical air currents push it back up, to the cold, high area of ​​the storm cloud, where it freezes. The block of ice that forms falls down, but the air currents return it up again, more water vapor freezes around it, and it falls, and then the air currents push it again, and it grows further, and returns for goodness sake. In this process, which is repeated several times, the lump of hail accumulates more and more layers of ice, until it is finally too heavy to rise again, and falls to the ground.

Usually hail balls reach the size of a pea, but under suitable conditions and with strong enough winds they can also reach huge dimensions and form an ice ball 20 cm in diameter and weighing almost a kilogram (although this is quite rare) as happened in Tripoli, Libya in October 2020. The layers of ice that form during the fall and rise cycles of the hail can be identified by the block of ice that reaches the ground, similar to the rings of trees or layers in sedimentary rocks.

The locust is a real blow, which strikes again and again in different parts of the world even today. The last major eruption occurred about a year ago, when hundreds of millions of flying insects covered the skies in East Africa and the Arabian Peninsula, destroying vast areas of agricultural crops. How do such destructive swarms form?

When they are not together in groups of millions and more, locusts are simply grasshoppers, similar to those we also see in us jumping in the grass. But there are species of grasshoppers that are able, under certain conditions, to form a giant swarm. This happens especially after particularly rainy years: the rain leads the grasshoppers to lay many eggs, so the next generation has many more details. When the weather gets dry again, the many grasshoppers crowd around the remaining vegetation, and the density causes them to change. When they rub against each other, serotonin is released in their nervous system, the same neurotransmitter that is also found in our brain. It causes many changes in grasshoppers, both behavioral and physical: they become larger, have stronger muscles, and even their color changes. Before the change the grasshoppers are solitary animals, and usually try to avoid the company of others, but after that they are attracted to each other and fly together from place to place. This is how the huge bands we know as locust swarms are formed.

A total solar eclipse occurs when the sun, moon and earth are on the same line, so the moon obscures the sun perfectly. Such an eclipse, in which the sun disappears in the middle of the day and darkness prevails on the earth – even if for a few minutes – occurs only once every 18 months at a time in a different place on earth. Every point on the globe receives one full solar eclipse every 370 years or so.

Not only are humans fascinated by such an eclipse, other animals may also change their behavior following a brief disappearance of the sun. For example, researchers from Mexico reported that spiders began dismantling their webs during a 1991 eclipse; Day-active fish in the Galapagos stopped eating and hid in coral caves during an eclipse in 1998; In Venezuela, at the height of that eclipse the birds flew to their shelters, and at the end they returned to the bay to engage in their affairs as if nothing had happened.

Solar eclipses also contribute to science. On May 26, 1919, a complete eclipse observation confirmed one of the most important assumptions in the general relativity of Albert Einstein and brought about one of the greatest scientific revolutions in history. Einstein predicted that the gravity of a large enough body would also affect light rays and cause them to curl, and suggested testing this during a solar eclipse, so one can see if certain stars would appear closer to us at the edge of the sun compared to their “normal” location at night. A delegation of British scientists photographed the eclipse, and despite difficulties and problems managed to measure a deviation in their location – just as Einstein predicted.

How do older siblings treat their younger brothers and sisters, not in humans but in wildlife? In most cases the older siblings go out to live independently before the next offspring arrives, or the next offspring lives. But this is not always the case: sometimes the older siblings still spend their time near the parents, and may help raise the younger siblings, and sometimes even interfere.

Among quite a few birds, the phenomenon of nest helpers is well known – adult offspring who help their parents care for offspring born a year after them, instead of establishing their own nest. The common sparrow in the country is one of the species that shows this behavior. There are several possible explanations for why the birds “volunteer” to help the nest: they acquire skills that will help them raise their chicks in the future, and help ensure the survival of their siblings, who are genetically close to them. In many cases, birds are more likely to stay with their parents when there is a shortage of nesting places, so their chances of establishing their own nest are quite small. The phenomenon is also seen in some mammal species, for example the African meerkats, which live in family groups and raise the pups together.

In monkeys young females sometimes help care for babies, but because slides mature slowly compared to other mammals, the older siblings are still “children” when the younger sibling arrives, and still want their mother’s attention. This often leads to conflicts and even to “tantrums”, with the big brother demanding that the mother take care of him, and even breastfeed him as well.