The owner of the Royal Botanic Gardens, Hooke, asked another profound question: "Ladies and gentlemen, the doctrine of sexual selection explains the minutiae of life and death very well, and suddenly I have a question—why would God make all creatures male and female?" What are the survival advantages of this? ”

This problem, which is almost unsolvable, is answered by the most imaginative Earl, who can even imagine the "replication mode of double-stranded molecules": "Imagine a living organism that is best adapted to a particular environment, temperature, humidity, air, soil, and, most importantly, other organisms there." It does not reproduce sexually, but when it grows to a certain extent, it splits into two identical individuals. What will happen?

It won't be long before the creatures will exist in a very singular way, since they simply copy themselves and there is only one environment that suits them best. So, they can't leave that environment, and even when the environment changes drastically, they all go extinct overnight, without exception. The diversity of offspring is a vital attribute of living things, and organisms that do not reproduce in this way have been largely eliminated for the long term. At present, only a small number of microorganisms and plants reproduce asexually. This phenomenon is even more pronounced in the highly competitive world of advanced organisms, where sexual reproduction is almost invariably achieved.

Let's go back to the hypothetical double-stranded replication. The original intention of this hypothesis was to simulate the union of the sex, one chain from the father and the other from the mother, and the child was born with obvious traits very different from that of both the father and the mother, because he was a life made up of a completely new genetic material. From human experience, it is clear that neither father nor mother can contain only one piece of genetic material, otherwise their children should all look exactly the same, and the reality is that only twins can look exactly the same. When we look at Princess Victoria, she looks very much like Her Majesty the Queen, but Princess Louise is more like Her Royal Highness Prince Albert. We will also find that the probability that children who are not twins will look exactly the same is very small, so the inheritance of humans is not only multi-stranded, but certainly not too few.

Is there any evidence for this hypothesis of multi-chain inheritance? Yes. My team did genetic results with Drosophila melanogaster and got reliable results. Fruit flies are a good animal, it only takes two weeks to reproduce a large number of offspring, and it can be counted with obvious patterns. And its multiple traits are easy to observe.

The actual yàn of Drosophila melanogaster proves that the genetic material is indeed replicated in the form of a double strand, and I will tell you about it. ”

The legend of the double-chain replication actually has real evidence, and everyone present was shocked, which was a shocking blow.

Tang Ning: "Our team first used two fruit flies with different wing shapes as real objects. Of the two types of flies, there is a 'remnant' fruit fly with small wings and no flight, and a 'long-winged' fruit fly with long wings that can fly freely. After the two fruit flies were crossed, the offspring produced were all long-winged fruit flies. Hey? Why are they all winged? Where did the stump go? Is it true that the appearance of the trait of the long wing will inhibit the residual wing? In order to answer this question, we need to do another test of the offspring of the first crossing.

Subsequently, our team mated the hybrid long-winged fruit fly (i.e., the first generation of the child) with male and female, and the resulting offspring (i.e., the second generation of the child) included both the long-winged fruit fly and the residual wing fruit fly. In terms of the number of offspring, 3/4 of the offspring were long-winged Drosophila and 1/4 were remnant-winged, with a ratio of 3:1.

What does this mean? Let's take a pen to calculate, there are only two genetic factors distributed on the two chains, one has inhibition for the other, called dominant, and the other is called recessive. The dominant chain and the dominant chain are together, of course, the dominant chain and the implicit chain are together, and the table xiàn is dominant, and the two should account for 3/4, and the remaining 1/4 is the residual wings of the recessive chain plus the implicit chain to show xiàn. ”

Except for people like Princess Victoria and Lady Cameron who came to make soy sauce without pen and paper, many people who took this salon seriously brought them, and Brunel, who was good at mathematics, even came to the conclusion that "it is indeed a double-chain copy that can explain such a number".

Wallace exclaimed excitedly: "It's amazing, there is also evidence for double-chain replication, it seems that creationism has really encountered a crisis, it turns out that I also think that the spontaneous change of this double-chain macromolecule from inorganic to organic is difficult to prove, haha, powerful!" No, I'll have to go back and catch fruit flies to do it myself! ”

Mrs. Cameron may never understand, and Princess Victoria, after much thought, finally understood the meaning of this 3-to-1, and showed admiration for the great scientist Count - such a shocking evidence. She couldn't help but ask Tang Ning: "Did you guess the double-chain mechanism a long time ago, or did you come to the conclusion after doing it?" ”

Tang Ning: "I guessed it a long time ago, well, yes, one day, I met a blue-eyed person, I chatted with him curiously, asked who in his family has blue eyes, I counted his number jù, and then did many similar surveys, the number jù is exactly 3 to 1, at that time, I was already imagining the law of double-stranded inheritance. ”

Talented! What a rationale and deep insight. Everyone bowed to him.

That's two pieces of evidence!

Darwin eagerly asked Downing the question: "What is the evidence for the hypothesis that the genetic factors are distributed on different double strands?" ”

Downing: "We also use a white-eyed fruit fly to make a real yàn. Originally, the eyes of fruit flies were red, and only a few white-eyed fruit flies were found by chance. I mated the white-eyed male fruit fly with the red-eyed female fruit fly, and the offspring were all red-eyed. This suggests that red eyes are dominant traits compared to white eyes.

However, when a white-eyed female and a red-eyed male were mated, the offspring were extraordinary: not only did both red-eyed and white-eyed flies have zài, but the males all had white eyes, while the females all had red eyes.

This illustrates two problems: first, there is a genetic factor that is decisive for differentiation, and it is combined with the genetic factor of eye color, so that it can be explained that they always appear at the same time. Second, the male genetic factor is dominant, as long as it is there, the fruit fly is male. The number jù is more complicated, I can't explain it for a while, but I will publish a related paper in the next issue of "Nature" to support our theory of evolution, so remember to buy it and read it. ”

So far, the 18 guests feel that the trip is worthwhile, (perhaps Mrs. Cameron is an exception, but she is also inexplicably happy for these people who have found the truth and are happy), and it is really a fruitful scientific salon.

In the midst of his joy, Director Hook threw another bombshell: "It seems that the Earl is a genius at explaining natural phenomena, and I have also observed a phenomenon: most plants are not self-pollinating, and although their pistils and stamens grow on the same flower, either because of different flowering periods, the pistils are not ripe when the pollen falls on the pistils, or they have already been pollinated. Either the ovary of the pistil has the function of filtering its own pollen. I think...... It must be that the offspring produced by self-pollination as mentioned by the earl just now are too similar and have no differential survival advantage. So, can this law be applied to people? I mean, can inbreeding produce children who don't have a survival advantage from an evolutionary point of view? Please forgive my presumptuousness, because I seem to have noticed that my relatives and friends, as long as they are married between cousins, it seems that the probability of a child dying is particularly high, and I did not carefully count the number jù, but it is quite obvious. ”

Alas, when it was finally time to talk about such an unpleasant thing, Tangning restrained his smile: "Yes, you are right. I originally wanted you to see the statistics I collected in the Nature paper, but since I talked about it today, I will talk about it. As mentioned earlier, the offspring of the same have no survival advantage, then, in other words, the species that has the ability to kill their own similar offspring has a survival advantage. As Mr. Hooke said, plants avoid self-pollination by means of different flowering periods, but what about animals? We can hypothesize that there is a genetic factor that can increase the rate of miscarriage in babies and also increase the rate of premature mortality in juvenile animals, and this probability increases significantly when inbred. When we see that a certain animal does not like to be close to the union, it is almost possible to conclude that they have this genetic material on their body, so the animal that does not like the close union wins because it has the ability to kill its own ** sibling. This is not a simple conjecture, I have sent to the major hospitals with detailed statistics, and I have come to a preliminary judgment that the current popular marriage between cousins has a high rate of infant death, and parents with a certain blood relationship are ranked second. ”

Downing looked at Darwin, consciously or unconsciously, and saw that his face was pale, and he remembered his wife, Emma, who was also his cousin, and then, his children who had died young. He had two daughters who died young, of which the eldest daughter, Anne, died of illness at the age of ten, which troubled Darwin the most. Darwin was always concerned about his family's consanguineous marriages, and his family had four cousins with the Wedgwoods. Now that Downing's "statistics jù" gave a resounding answer to his worries, how could it not make him sad?

Princess Victoria, who adores Downing, changed her voice: "I...... My parents...... Also cousins, isn't this ......"

Tang Ning said softly: "Don't worry, although the number is not good for the cousin's marriage, the probability is not so scary, judging from the facts, your brothers and sisters are all healthy and should be fine." Because in ancient times, the productivity of human beings was low, and many tribes only had so many dozens of people, and there was no way to find an outside tribe to marry, and sometimes the union between close relatives was also necessary. (http:／/.）。 Mr. Darwin, don't worry, I know that your eldest daughter died of tuberculosis, a disease that no one can cure for the time being, and it has nothing to do with genetics. Your second daughter died when she was very young, which is more likely to be the cause of the child's low immunity, and it has little to do with genetics. Disease-causing creatures are the abominable child killers. ”

Darwin's face looked a little better, but he suspected that Downing was comforting him.

Tang Ning was suddenly shocked, and said to Princess Victoria, "Vicky! If I invent a medicine that can save tens of thousands of people, will your mother give me a duke to be a pawn? ”

Princess Victoria nodded vigorously: "Hmm! I think it's okay. How? What do you think of? ”

Count Guan Fan said with a smile: "Microorganisms will definitely encounter enemies in the process of evolution, what I want to do is to find out the enemies of disease-causing microorganisms, and then use them to deal with those terrible diseases, such as tuberculosis." ”

I don't know why, just listening to Downing's words, everyone is very confident in his new drug, not only in the survival competition of evolutionary theory, but also in Downing, who has invented a variety of anesthetics and analgesics.

Hugo asked curiously, "Why is Downing so interested in knighthood?" "As a Republican leader, I don't understand Downing's mind.

Alexandre Dumas laughed and said, "Because someone has a crush on a certain duchess and hopes that he is also a duke, he is worthy of a beautiful duke, am I a genius?" ”

Heck, how did it get to the UK? Tang Ning smiled and accepted the jokes of his friends.