The origins of sexual attraction may be older than you think

Beijing time on November 19 news, according tomedia reports, it is difficult to observe the sexual intercourse process of single-celled organisms. “Suppose you’re a Martian looking at Earth and wondering if humans are going to have sex,” said John Logsdon, an expert on early nuclear biomass at the University of Iowa. But if you can’t see through the window and into the house, you can hardly see the crackling human beings. “

The origins of sexual attraction may be older than you think

Many single-celled organisms are able to reproduce asexually (i.e., clone themselves) as well as sexual reproduction (i.e., their DNA binds to another body to produce new offspring), and they are more likely to clone.

It’s really strange to think of a creature willing to have sex. Sexual intercourse not only makes organisms vulnerable, but also requires males to spend a lot of energy courting to complete a complex process of combining their DNA with other organisms.

Cloning is much simpler. For a long time, many scientists believed that the common ancestor of all egos (including animals, plants, fungi, slime bacteria, and everything but bacteria and ancient bacteria) adopted this reproductive strategy. But Mr Rogston said: “We don’t know much about it. “Biologists were shocked by their findings after studying and analyzing the origins of different nuclear organisms. Now they believe that even ancient nuclear organisms have sex. The basic elements of sexual behavior – the exchange of attraction and genetic material – may have emerged much earlier than sex, and much earlier than the familiar relationship of “man, woman, baby”.

“The concepts of male and female evolved very late.” Sarah Otto, a zoologist at the University of British Columbia, said. If sexuality and sexual attraction occur much earlier than gender, sexual attraction must be more than just about gender differentiation and gender.

When Rogston first thought about ancient nuclear biological behavior in the early 2000s, he thought so: since many single-celled ucleus organisms can reproduce without mating, genes can be used to determine which organisms have sex. Some creatures, he speculates, have genes that determine gender, while others don’t.

But Rogston’s findings exceeded his expectations: all the ucleotrons he examined had gender-related genes, but not all of them were used. This means that the “last common ancestor of the celibacy” (i.e., the ancestors of all the true nuclear organisms, from humans to slime bacteria, referred to as LECA) must have had sex.

“These creatures don’t leave a fossil record,” said Joseph Heitman, a microbiologist at Duke University. “If you ask scientists to answer how microbes have sex, they might give the following answers:

About 2 billion years ago, a lone LECA creature was swimming through a crowded ocean. “Imagine you’re in a vast sea, surrounded by all kinds of creatures, and you can’t see a potential mate.” At this point, suddenly another LECA creature swam past and noticed the LECA in front of it. Next, they start “courtship.”

“Even for them, sexual attraction is important, they put a lot of energy into making themselves more attractive, ” Otto explains. ” “

LECA creatures can’t see or hear, but they can smell. The “perfume” they use is Ferlomon, the biopic that many creatures use. These substances are extremely effective. Duncan Greig, an expert on yeast, points out that tweezers can sense similar Ferlomon from miles away. LECA creatures also use Fallomon to seduce each other.

“It’s like beckoning at each other, in a sense, it’s a courtship.” Greg explains.

Fallomon can make these LECA creatures realize that they belong to the same species. In an ocean full of bacteria and ancient bacteria, LECA organisms do not want to send autumn waves to each other with other single-celled organisms.

But there are also differences between Fallomon. Creatures that can release more Ferlomon will be more attractive. After all, they can use more energy to secrete Ferlomon, suggesting that they are more powerful.

“It’s like knights competing with each other to get the princess’s heart.” Greg added.

And that’s a really useful trick. LECA creatures are captivated by each other, undergo subtracting splits, and then give birth to cloned offspring that have only half of their DNA. These newborn “semi-LECA creatures” swim back to each other, and when they are close enough, one of them shoots out a “handle”, the modern fungus’s so-called “shmoo”. And another LECA creature shoots its own handle. When the handles touch each other, the membranes of the two LECA creatures also fuse with each other, and the overall shape looks like the bones painted in the cartoon.

“These two creatures are not sperm and eggs, they are just two cells that bind together.” Otto explains.

When the cell membranes merge, the two cells become like large cells. Their nucleies are also merged, and DNA is mixed.

“It’s like washing two cards together.” “But it’s not really going to work, because the two cards are exactly the same, ” says Mr Rogston. “Humans still do this, and when sperm binds to eggs, the membranes and nucleuts of both cells merge with each other.

Once the DNA of the two “semi-LECA creatures” is mixed together, they form a complete LECA, and a “child” is born.

Two billion years later, all living things have enough genes to randomly “shuffle”. But some organisms have sex, some have asexual reproduction, and others switch back and forth between the two ways. Many creatures are male and female, such as most plants. Some species are gender-neutral, and the reproductive process involves only the merging of cells. Some fungi have as many as tens of thousands of genders.

“Once you understand that living things have such a variety of breeding methods, you realize that the idea of sex between males and females is just the tip of the iceberg.” Mr Otto said.

After the biological evolution of gender differentiation, the difference between the sexes was not very large at first. Instead, single-celled organisms need to evolve specific markers to let each other know that they belong to different species. For example, these creatures may have type A and the exact same type B, which can mate with each other. Or it could be dozens, if not hundreds, of different types. The general principle is to avoid mating with your “close relatives”. If you belong to Category A, you may only be able to mate with Category B or K.

True gender evolved from these different types later. But gender is still not the only factor in decisive intercourse and attraction. Even today, for many species, “attractiveness is crucial, but it’s not just males that attract females, or females that attract males.” There are differences regardless of the dimension. “

Humans are no exception. Otto added: “We always think of gender as a gender, but gender is actually more fluid and multi-dimensional. Simply dividing us into two categories is not in line with evolutionary tendencies. (Leaves)