Baby Beasts: Love and Evolution in the Animal Kingdom. Evolutionary success is not about the number of children one has, but the number of grandchildren: children need to survive and pass on their genes. David Attenborough, asked a few years ago by journalist Joanna Nicodemska about the animal that he finds most interesting.
And after considering it a bit, replied that he is most fascinated by the three-year-old human child, whose ability to grow and adapt is simply limitless. The same journalist and I have been asserting this opinion for eight years; indeed, observing the evolution of a juvenile representative of the Homo sapiens species is an ongoing and fascinating adventure.
It is a fact that evolutionary success is not determined by the lifespan of adult individuals, but by the number of descendants who carry their genes to subsequent generations. More precisely, it is not about the number of children one has, but about the grandchildren: children need to survive and pass on their genes.
Of course, in order to have babies, one must produce them, or at least somehow initiate the development of eggs, as in parthenogenetic species, where females do not bother with children at all, or only almost never. But I’ve already written about the various basic ways to accomplish that first step, so let’s focus on what happens next.
Ecology distinguishes two breeding strategies: ‘R selection’ and ‘K selection’. The symbols are derived from a complex formula describing population dynamics developed in 1838, which organized our thinking about the success of animals for the remainder of the 19th and almost 20th centuries. It was developed by Pierre François Verhulst (1804-1849), and its simplified version is as follows: dN / dt = rN (1 – N / K), where N is the population, r is its maximum growth rate, K is the carrying capacity of the local environment, and dN / dt is the rate of change of the population over time.
According to this model, the species that participate in the R selection produce as many offspring as possible, while the K selection implies an investment in quality rather than quantity. So either we have a horde of children that we are not too worried about, hoping that things will go well and some of them will survive; Or we have some, but we invest a lot in them and try to make sure they work as well as possible.
Of course, as is often the case, in nature it is more of a continuum, where not just different species, but also individual individuals of the same species, operate somewhere in between these extremes and we can only tell if one is ‘plus R’ or ‘more K’. For example, guppies, small fish from South and Central America popular with aquarists and evolutionary biologists, are very flexible in this regard.
Researchers have been studying them in the streams of Trinidad and Tobago for years and have found that their tactics vary greatly depending on the presence of predators, sometimes within a few meters. In the upper reaches of streams, where reefs make it impossible for larger fish to pass, guppies are less frequent.
But the bigger and better fed the young, then they are ‘more than’, and their young grow peacefully in calm waters. Beneath the rocks (sometimes literally everything about a rock) they choose a strategy more closely aligned with the r-selection: their young are smaller, but they are much larger as they must be eaten. It makes sense to be as exposed to constant risk as possible.
So even though science is currently reversing this classical model, speaking more often about the diversity of survival strategies, I am of the opinion that, with some reservations, these two characters describe a complex reality for us. However, no matter how many children there are, they have to be brought into the world in one form or another.
Here, there are basically two methods. You can put an egg with yolk (evolutionarily similar to a packed lunch), from which after a while, with more or less help from the parents, your babies will be born; Or you can nurture the offspring within your body and give them a ready birth. It is a simple assumption that there is a third option in addition to oviparity and vitality: ovoviviparity. It refers to the embryos that develop into eggs that still remain in the mother’s body, which are then released by the young.
All the eggs in one basket?
Let’s start with Ovo now. The egg must be wrapped in something, so as to protect the embryo from the least external danger. Species that lay eggs in water usually don’t have to worry about them drying out, so a gelatinous membrane is usually sufficient for them; This means that the contents of the egg stay where it should be, instead of moving.
But if you live on land, like many insects and arachnids, and all reptiles and birds, as well as mammals like the platypus and echidna, you should invest in a little more water. The hard shell of a bird’s egg also protects it from at least some predators. For example, the shell of an ostrich egg, by the way, the largest single cell in the world, is so thick and strong that even lions have trouble breaking it.
Blue eggs in a bird’s nest
Still, everyone who is encased in eggs has a better chance of surviving if someone takes care of them. We automatically combine the incubating eggs with the birds; In fact, they take care of their own claws or force someone else to play the cuckoo. But other animals also provide many examples of parental dedication.
Female octopus spend the last weeks of their lives protecting their eggs, some digging in underwater corners, oxygenating them and protecting themselves from algae and parasites. This work consumes all the time and energy left after a great effort to lay and lay eggs in a suitable place. When the young octopuses finally have babies, their mother is already dead or is about to die.
Although this strategy seems favorable for cephalopods, we owe it to our current position in the world: I suspect that if an octopus mother could pass on her knowledge and experiences to her offspring, Earth would be a very different place. Regardless, despite its amazing intelligence, every octopus must reinvent the wheel.
Since his intelligence dates back a few million years, I truly believe that if they could accumulate experience from generation to generation, he would have been writing this text for an eight-legged editor-in-chief, even that. in the opinion of a creature as inferior as man. Although the sacrifice of the cephalopod mother is impressive, some invertebrates go further.
Perhaps the most extreme form of parental devotion is marriage, or the consumption of a mother by her newborn. This phenomenon can be observed in some species of arachnids: after laying eggs, the female begins to dissolve her body tissues with digestive juices, so when the adorable spiders are born, their mother is placed in an eight-legged chitin container. more than nutritious juice.
The tattoo just needs to be cut through her skin and they can adopt it. Among insects, aside from the obvious examples of hymenoptera (i.e. ants, wasps, and bees) and termites, earwigs provide another example of exemplary parental care. The Japanese species Anachura harmandi is the only insect known to science in which the mother also dies before the baby is born, becoming her first meal.
Even the common earwig is no stranger to maternal sacrifice. The females of these unpopular and courageous aphid and silverfish victors often gather in groups to guard their claws and then to feed their young and bravely defend them from predators.
Egg laying has its obvious advantages. If they don’t require care, you can not only produce several, but you can also expect them to spread around the world on their own. But carrying their offspring in their own body makes it easier for parents to provide the right conditions for development. It is not surprising that some animals (including many species of sharks and the common European viper) have chosen to compromise ovoviviparity during their evolution.
In others, as in viviparous lizards, one or another method of reproduction dominates depending on the environmental conditions. Like most species of lizards in southern Europe, these lizards lay eggs. But in colder areas the female gives birth to her young. Thanks to this flexible strategy, they can live in environments inaccessible to many other species, such as high in the mountains and in the far north of Europe.
It is the only reptile on our continent that also lives beyond the polar circle, although snakes, the northernmost of our snakes, reach almost as far north. Another interesting topic is laying their eggs in someone else’s body, although I’m not sure if this still counts as ovoviviparity.
The most common and harsh examples are the many species of parasitoids – animals that completely exploit their host, living in it for a time, before killing it like the aliens from the famous science fiction movie. Many wasps paralyze their prey (usually a caterpillar or a spider) and lay their eggs in that living fat; Later, the larvae will slowly make their way. But laying eggs in your own partner’s body is even more interesting.
This is what happens in the hippocampus, or the slow-moving fish known as seahorses. After their mating dance and the successful termination of the relationship, the female deposits the fertilized egg in a special bag in front of the male. From then on, she would be left under her care, so that one day she could give birth to hundreds of miniature seahorses, which she would care for after birth.
But since I was little I have been fascinated by other creatures. The common toad of Suriname, a tailless amphibian (that is, adjacent to a frog) from the northern part of South America with the catchy Latin name Pippa Pippa, appeared in my life as an illustration in an ancient atlas of animals, e immediately took off. as one of my favorite species of the time.
Immediately after the female lays her eggs, the male picks them up and distributes them evenly over her sticky back. her skin becomes spongy and the eggs sink into it and develop relatively safely; After a while, the fully formed frogs release it. This is undoubtedly one of the most interesting births in nature.
The strongest bond
If the baby is not separated from its mother’s body by the shell of the egg, she usually feeds it through the placenta. This is, of course, the case for most mammals, but not exclusively. The placenta can also be found in some sharks and lizards, but true placentation has evolved independently at least 150 times and occurs in many species of fish, amphibians, insects, and arachnids. One of these unexpectedly loving parents is the notoriously annoying fly.
The female flies for nine months with a single growing larva in her abdomen, feeding it a nutritious milky liquid. A more formidable version of the young feeding of it can be seen in some Gymnophiona of the common caecilian family. Her embryos have special teeth that allow them to feed on the epithelium of the mother’s oviduct. After they are born, the young migrate to the outer epithelium of the common caecilian female and literally drive her away, although fortunately she regenerates quickly.
After leaving the mother’s body, in some way, many young animals still require constant care. Because the physical connection no longer exists, it is necessary to initiate a psychological bond to persuade the parents to provide food and shelter. Parents should continue to care for their newborns or babies who are born.
And so evolution has equipped young animals with an arsenal of signals that leave their keepers helpless. In birds, it is often a blurry coloration of the area in and around the beak, which is visible when fully open. Adult birds find this irresistible and feed in the open air, begging, even if they are not their young, but for example, fish taking advantage of the situation.
It is due to our own primitive instincts that most of us also feel an urgent need for tenderness and care for young animals (or those that appear young). Plus, the recipients of that care don’t even need to be cute bunnies; I still remember finding a turtle nest in a nest box that I was looking for when I was a student.
The chicks of this woodpecker, with their thin, twisted necks and flat heads, look like mold-infested hallucinogenic mushrooms and they certainly aren’t pretty, but it works. Their relatively large eyes and husky voices are enough to make up for it. Of course, if the animal meets our beauty criteria, the effect is even stronger.
Cats take advantage of this openly – their tiny faces, big eyes, and meows that mimic the voice of a human child become so alluring that even my geological friend can’t resist them. Although due to his profession he is used to communicating with nature through a hammer, he cannot contain himself and constantly gifts everyone on social media with images of his feline loyalties.
However, there is no doubt that it is not just a simple reflection in animals such as birds and mammals. For some time now, researchers have increasingly boldly asserted that other animals also experience emotions and feelings, such as fear, anger, boredom and love. And love for your child is perhaps the easiest.
This is the simplest explanation for dramatic examples such as the behavior of an orca named Tahalequa, who two years ago carried the body of her dead baby for 17 days. Parental love can also be an explanation, like there is no other, of richer and more agreeable examples of behavior, such as the fact that I am about to take my daughter to school, even though I have spent all the time. night reading this lesson. spent writing.