Among the scientific news of the week:
- Is it possible to survive without sex (yes, if you are a tick)
- At the genetic level: how dogs understand humans
- Found Rome and disappear: where did the mysterious Etruscans go?
Six million years without sex
Let's be honest, sex isn't worth it. Indeed, so much effort, and for what? Isn't it easier to reproduce without outside help and unnecessary headache?
Alas, evolution dictates its own rules and punishes severely for the lack of sex. Sooner or later, all eukaryotes (living creatures whose cells contain a nucleus, including us humans) are forced to exchange chromosomes to maintain gene diversity or be on the verge of extinction.
This is a general rule, but the shell mite Oppiella nova decided to become a rare exception and refused to have sex. At all.
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- Stick insects: a million years of evolution without sex
These tiny, one-fifth of a millimeter, ticks have two copies of each chromosome, and this allows us to classify them as diploid (that is, containing one or more chromosomes in more than double number) organisms, just like you and me.
But at the same time, comparing its genome with the genome of a close relative, the tick Oppiella subpectinata, the training came to the conclusion that this unique took a vow of celibacy several million years ago, and at the same time continues to successfully survive!
The exchange of chromosomes and their mixing allows you to create many genetic combinations that can play a decisive role in difficult times: if a plague happens, the climate changes dramatically, or a deadly new predator appears, everyone will die, but there will always be several individuals who will be able to resist this and continue the race …
Actually, sex is about this, but everything that accompanies it – from finding a partner and fighting for him to the difficulties of pregnancy – this is the high price that one has to pay for genetic diversity.
But there is another way to maintain gene variation without resorting to sexual reproduction. It is a process of mutation in the same genes, allowing for the creation of a unique gene signature in asexual organisms.
Such a mutation, known as the Meselson effect (named after the Harvard geneticist Matthew Meselson), with good reason, makes it possible to call a diploid organism an asexual, that is, a sexless species.
However, the problem with the Meselson effect is that until now no one has been able to provide unambiguous evidence of its manifestation. So, some ancient species, considered asexual, in fact turned out to be not so ancient, other supporters of abstinence – what a scandal! – turned out to be lovers of orgies that greatly diversified their genes.
And scientists needed strong evidence of genetic variability in an animal that had abandoned sexual reproduction for a very, very long time and never returned to it.
This led them to the armored ticks O. nova, which separated from a common relative of all ticks from 6 to 16 million years ago and since then demonstrated the action of the Meselson effect in practice, successfully multiplying on their own.
Given the size of these ticks, scientists had to tinker a lot, first in order to find them, and then to extract the genetic material. Then it was necessary to create a special program for DNA analysis, but in the end the researchers were rewarded.
“The results of our analyzes have unequivocally proved that O. nova reproduce exclusively asexually,” emphasizes the author of the study, a specialist in reproductive biology at the University of Lausanne, Jens Bast. surprise”.
Of course, scientists admit, these ticks are a rare exception, and asexual reproduction also has enough disadvantages. However, 6 million years of successful life without sex speaks volumes.
Proven: Dogs Are Programmed To Understand People
Dogs understand their owners perfectly. Sometimes a tiny gesture is enough for a command or desire to be happily fulfilled. And after all, not all dogs have undergone special training or education for this. This is innate, scientists say.
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“The ability of dogs to communicate with humans has allowed them to fill a unique niche in their neighborhood with humans,” says Emily Bray, a canine cognitive researcher at the University of Arizona at Tucson (published in Business Insider). “Many of the assignments they are for us perform, from hunting to guarding functions, related to their ability to understand our clues. “
Of course, in order for such cooperation to be mutually beneficial, the dog needs a reward, and here scientists made a discovery: it turns out that four-legged friends perfectly distinguish a well-deserved reward from one that accidentally fell out of the pocket or was deliberately held for edification.
In the course of the experiment, a man and a dog were separated by a barrier with a small gap through which a treat could be inserted, while, if desired, the dog could bypass the barrier.
The award was given in three ways: first, it was pulled through the slot, but then “unexpectedly” it was dropped with a characteristic cry oh. Then, it seemed, they wanted to give the award, but it did not “fit” into the slot, and, finally, the cookie was first held out, and then with a laugh they pulled back their hand.
The results showed that in the latter case, all dogs waited much longer before looking for a workaround. But they immediately rushed around, when they realized that the reward was waiting for the hero, but for some reason there was a delay.
According to scientists, this proves that dogs distinguish accidents from patterns in the behavior of their owners and act accordingly.
Bray and her colleagues have previously experimented with two-month-old puppies at a company that trains service dogs. There were about 400 of them, so the animals had practically no individual contact with people.
The puppies were given the command “Look!”, After which they looked into their eyes and pointed with their hand to the place where the reward was. The puppies were successful in finding treats, and since their response did not improve over the course of the experiment, Bray and his colleagues concluded that skill was not part of the learning process — dogs were already genetically born with the ability to understand our intentions.
The findings of Bray and her colleagues are supported by a comparative analysis of the behavior of puppies of dogs and wolves, from birth, were in constant contact with humans in a wildlife center in the US state of Minnesota.
The researchers decided to see how quickly puppies of dogs and wolves can find a treat hidden under one of two inverted bowls, guided by the direction of the person's gaze and finger.
Dogs were twice as successful at coping with the task, despite the fact that before that they had not had as much contact with people as wolves. Many puppies solved the problem the first time, which indicates that they did not need any preliminary training at all.
“Dogs have a better human understanding than wolves from birth,” explains Hanna Salomons, co-author of the study at Duke University in North Carolina.
The experiment also showed that the likelihood of a dog approaching a stranger is 30 times (!) Higher than that of wolves, as well as the fact that when performing a difficult task, dogs are much more likely to turn to people for help. The wolf tries to do everything on his own, justifying the established image of a loner.
Strangers among their own: how the Etruscans preserved their culture and language
Etruscan feast scene
For many centuries and the emergence of the Roman Empire on the Apennine Peninsula, a completely different culture dominated and other people lived – the Etruscans. They were skilled merchants, farmers and artisans who traded with their neighbors in the Mediterranean.
But at the same time, their civilization, centered in modern Tuscany, was much more developed than that of the same neighbors, women were endowed with great rights, the level of art was an order of magnitude higher, and even the language, as far as can be judged from the surviving fragments of writing on the tombs, was completely not like the rest of the languages of Europe of that period.
Herodotus was interested in the history of the Etruscans in about 500 BC. In his opinion, they came from Anatolia and brought with them the language and culture of those places.
Meanwhile, as evidenced by the results of a new study of the DNA of the Etruscans, they did not differ genetically from their neighbors.
A group of archaeologists, linguists and geneticists led by Cosimo Post from the University of Tübingen, based on the analysis of dozens of skeletal samples, is taken to argue that the Etruscans, at least in part, were descendants of Stone Age farmers who inhabited Europe for 6 thousand years BC, then have had the same roots as the Latins.
And, like its neighbors, around 1600 BC. they received a stream of newcomers from the steppes, from the territory of modern Russia and Ukraine.
“The Etruscans did not differ in any way from the Latins, and a lot of steppe blood flows in their veins,” says Post.
But what about the language then? Indeed, together with the steppe nomads, the Indo-European languages came to Italy and the rest of Europe.
“Usually, with the arrival of Indo-European languages, other languages were supplanted,” notes co-author of the study, a linguist at Leiden University Gus Kroonen, “so how did it happen that the Etruscans continued to use their language?”
According to scientists, the language and culture of the Etruscans turned out to be especially immune to such an “invasion”. Apparently, the newcomers who made it to Tuscany learned Etruscan themselves, married locals and became part of Etruscan society.
“If almost everywhere in Europe new people began to dominate and a new language along with a new culture, this did not happen here,” says co-author of the new study, historian at Harvard University Michael McCormick. “The old culture continued to flourish, and the Etruscan language was used for another 800 years. until Rome began to dominate the region and Latin quietly drove Etruscan into oblivion in the first century AD. “