Why did evolution lead in the direction of two interdependent couples for reproduction, instead of allowing us to reproduce with ourselves?
By: Lotem Eliyahu
The biological need to reproduce brings us, and many other species, quite a headache. Finding a suitable partner is not an easy task, you have to sing serenades, bring flowers and chocolates, build a proper house and more. So why bother? Why did evolution lead in the direction of two interdependent couples for reproduction, instead of allowing us to reproduce with ourselves? This is one of the oldest questions, and scientists have already hypothesized the answer, but now there is also an experiment that proves it.
A memory jog that will take you back to your happy middle school days, reminding you that the biology teacher talked about there being another sex. There are living things that do not need partners in order to reproduce. The intention is not asexual reproduction in which a genetically exact copy of the parent is created, but sexual reproduction, which includes sex cells only... well... with yourself. One example is Virgin reproduction in which a female can produce other females.
This method seems incredibly effective and at first glance it is expected that they will have a dizzying evolutionary success - first, they managed to ensure that all their genes are passed on to the next generation (Selfish genes incredibly), while breeding with a partner means that only half of the genes are passed on to the next generation. Second, males are a waste. The need to produce males means twice the production of females. When the female can breed with herself there is no double cost of time and effort to produce males that are not needed.
But, after all, breeding with mates is the more common strategy in the animal world, so it must have advantages that compensate for the disadvantages. The scientists usually list two main advantages. The first, mixing genes from two parents creates offspring with greater genetic diversity, which increases their chances of dealing with changes in the environment, predators and parasites. The second advantage is that shuffling the genes prevents bad mutations from accumulating.
The thing is, scientists like to prove their hypotheses, no matter how logical they sound. In this case, it was very difficult to test these two advantages in an experiment. Of course, the difficulty did not stop the scientists, and so, Levi Moran from the University of Oregon and his partners showed, in an article published this week inNature, that both explanations are correct, by manipulating the evolution of the nematode Caenorhabditis elegans.
Like humans this worm has two sexes but unlike us, the worm has males and there are hermaphrodites (both male and female in the same individual). The frequency of males in the population is only one in two thousand, so in fact most of the population, the hermaphrodites, can fertilize themselves. Hermaphrodites can also mate with males or other hermaphrodites, but they only do so about one in 20 times.
The reason Moran chose this particular worm is the genetics of C. elegans, which is so well-known and well-known that the researchers were able to create two genetic lines of hermaphrodites - one always chose to breed with another worm and the other always chose to breed with itself. The next step was to see how the two genetic lines he created would stand up to an evolutionary test. For comparison, the new lines were tested at the same time as normal worms. The first test wanted to examine whether reproduction with a partner really helps eliminate destructive genetic mutations. Some of the worms were exposed to a chemical called EMS (ethyl methanesulphonate) which causes the rate of DNA mutations to increase 4 times, and increases the chance of such a destructive mutation appearing. To make matters worse, the worms were transferred to a new environment that would weed out all the worms that were not suitable to survive in it.
Despite all these challenges, the genetic line that always bred with a partner remained successful even after 50 generations and was much more successful than the line that only bred with itself. Even the common worms have switched to a strategy of mutual fertilization under these harsh conditions. This is an example of how breeding with others is a way to remove bad mutations from the population. Moran estimated that the genetic burden on the line that reproduces only with itself will bring them to extinction within a few hundred generations.
Moran also exposed some of his worms to a bacterium called Serratia marcescens, which is so deadly that it kills 80% of the worms infected with it. It was a test of the ability to quickly adapt to new conditions, which results from having a wide genetic diversity. The worms breeding with partners passed the test successfully. They quickly evolved resistance to the bacteria while the self-reproducing worms did not. As in the previous challenge, here too the normal worms moved to reproduce with partners under the threat of the bacteria. So both theories are correct - compared to breeding with yourself, breeding with partners allows you to avoid destructive mutations and enables rapid adaptation to new challenges. According to Moran, a species that would evolve in the direction of reproduction with only itself puts itself on an evolutionary path with no way out.
Reference: Nature doi:10.1038/nature08496
The blog from which the idea for the article came
Link to image source
35 תגובות
He simply conducted several experiments and each of them was conducted with some of the worms. that's it. If he used "all" the worms in one experiment, he would have no worms left for the other experiment.
The sentence in the article "Some of the worms were exposed to a chemical called EMS (ethyl methanesulphonate)" is not clear.
If only a part was exposed, then the descendants of that unexposed part, from the self-breeding line, will never become extinct.
Michael, I haven't thanked you yet, so.. thanks
interesting,
By the way, the two most intelligent authentic human groups in the Jewish people, according to completely objective tests, are the Lithuanian group and the Yemeni group. The common denominator for these two groups is the existence of historical circumstances that led to the infiltration of genes from the environment under unique circumstances: in the case of the Yemenis - infiltration in a high dose in a short time due to Muhammad's massacre of most of the Jewish tribes in the Arabian Peninsula, an infiltration that came on an already diverse genetic background from previous historical periods. The sources of the penetration were the wholesale liberation of slaves, when it was necessary to sustain the generation, and of course cases of rape. For the Lithuanians - the fact that Christianity arrived in Lithuania relatively late (about 500 years ago) allowed free processes of conversion and the buying of heathen slaves and in any case their emancipation
– until that quite late period. The result was an extraordinary burst of genius in the following centuries (in the history of the Torah world, in this context, they speak of 'Lithuanian geniuses').
It turns out that the impact of the aforementioned historical processes remains to this day, and is even amplified today in Israel through interfaith marriages on a very large scale (over 40% of couples in Israel marry in interfaith marriages. This figure does not apply to the ultra-Orthodox Ashkenazi group, which has undergone a process of internal sectarian mixing, and no longer continues with external sectarian mixing).
I am not saying that all the unique phenomena of intellectual error can and should be attributed to these historical processes in their genetic meaning - but they can be attributed a significant weight in causing the special intellectual phenomena, together with factors of purely cultural diversity.
The article was very interesting and equally the discussion between Michael and Eddie was very interesting and I must state that I am quite on Eddie's side.
http://www.ted.com/talks/dan_dennett_on_dangerous_memes.html
Michael Rothschild: Indeed your argument is idiotic. Too bad you started it.
Eddie:
I'm sorry but I'm tired of the idiotic discussion you're trying to drag me into.
Michael Rothschild,
The problem with you is that you measure the achievements on a quantitative level.
According to the same logic, the fly is a more successful creature than man - it is much older and successful in its survival. According to the severity of the expected threats to the human species, it is doubtful whether the range of existence of the human species will even come close to ten percent of the range of existence of the fly species.
Are you really unable to test things on a qualitative level? Do not believe…
The Jewish genius was not 'carefully selected' - most of the Jews who disappeared into Judaism (in extermination and annihilation) did not disappear because they were less intelligent. What made the remaining Jews successful and survive despite everything - this is the virtue of their Judaism.
It is easy to get caught up in specific national disasters and in a demagogic discourse to allow a biased impression and to undermine the overall balanced perception and assessment of the Jewish reality. It is a fact that the Jews survived much longer than the ancient Egyptians, the Assyrians, the Babylonians, the ancient Greeks and the Romans - all great nations and empires that brought destruction to the Jews, 70 in turn, in dimensions that, relative to the extent of the Jewish population at the time, exceeded the destruction in the Holocaust. For example: in the period between 135 AD and XNUMX AD, close to two million Jews were killed in the Land of Israel and Alexandria, by the Roman authorities and forces. And the number of wounded, sold into slavery and prostitution who donates...
But the above should also be put in proportion. The important points are a. that the dimensions of murder were not uncommon in the ancient and old times. See for example the misdeeds of Timur Lang - one of the greatest conquerors and murderers in history. and B., and it is the more important point - that of all the other peoples - the murderers and the murdered alike - no cultural ethno-entity remained. What remains of them is a historical memory and only sometimes a certain cultural heritage. Only the Jewish people - survived in the ethnocultural sense, and how.
From this we can get a more proportional scale on the Holocaust: the Jewish people survived the Holocaust - for the most part, built a state, and not least of all. In the face of the objective difficulties, this country, despite all the ups and downs, is a tremendous success. What other people did this?
By the way, we forget that the Germans lost 18 million souls during WWII, about a third of their size. This is not comforting - but from this we see another evidence that even losing a third of a nation does not signify anything about a nation's survival weakness.
I did not claim that Einstein's similar achievements were achieved 'for Judaism'. I only claimed that they were achieved by Jews (and sometimes also by half-Jews - such as the physicist Bor and many others) - because genetic genes and intellectual cultural genes - Jewish - were assimilated into them. By the way, if you read biographies of Einstein you will find that he himself wondered about the Jewish genius, which is also in him, and attributed his success and the success of other Jews of his kind to the fact that they were Jews.
It is said with humor not entirely devoid of seriousness about the Torah genius known as the 'Rogotsuber' (Lithuanian Torah genius from the first quarter of the XNUMXth century) that his mind could hold four Einsteins and one more Bialik. As someone who knows some of his work, I can certainly agree with that. Geniuses of his kind were not rare. The Einsteins of all kinds, with all the great respect for their achievements - were not the pinnacle of Jewish intellectual and moral ability (and by the way, as a moral personality Einstein was quite a failure). Imagine what would happen if these geniuses were engaged in mathematics and physics... and I am not talking about the achievements of the Jews in past generations. In any case, these geniuses should also be taken into account, no less than the Einsteins of various kinds, in the assessment of Jewish genius. In any case, if it weren't for this authentic Jewish genius, it's hard to see how Einsteins, Perelmans and the like would grow at all...
In the meantime, I recommend that you study and consider objectively and with common sense the historical data, separate from anti-Jewish sermons, avoid secular religious fanaticism, and yes - behave with a little humility and respect - despite your personal anti-religious views.
Good luck.
And of course Christians also believe in virgin reproduction in humans.
A different type of intermediate state is exemplified by different types of ants and bees.
Elijah:
Actually there are and some of them were even mentioned here.
http://en.wikipedia.org/wiki/Hydra_(genus)
Let's go back to sexual reproduction.
Is there an explanation of how it developed? It seems to be an evolutionary "leap". There are no intermediate states between the two types of reproduction.
Eddie:
As the oldest monotheistic religion you would expect Jews to have more achievements than any other religion (because you would expect them to have more believers).
she does not have.
It has less achievements than Christianity.
True - it's more when divided by the number of skulls, but that's just an excuse.
In total it is less.
The Jewish genius was carefully selected over many years and it expresses above all the death that was the lot of the least talented of the Jews.
I was interested to see you deliver your sermon to the victims of the Holocaust - just before they went up in smoke.
You would probably get a standing ovation because they would surely have been willing to sacrifice their lives so that Judaism could be proud of its achievements.
It's interesting, by the way, that most of those you brag about the achievements they achieved "for Judaism" did not believe in it at all.
Michael Rothschild,
It is a fact, that in the case of the Jews there is no doubt that the religious memes center around them all the other memes, and are the basis of the most special genius in humanity in almost every field. And they surpass all the memes of all other ethno-cultural groups.
Leave the quantitative approach - go for the qualitative approach. It is not the quantitative survival that is decisive here, but the qualitative success. You will not be able to find so many peaks of intellectual and cultural achievement at all in any other defined group, consistently and over such a long historical period.
Rather, the smaller quantitative survival highlights the quality dimension, and actually, in a historical account - it derives from it. That's why I have no problem identifying as a Jew and not as a Hindu (and I'm not impressed by their idolatrous and at best pantheistic and simplistic 'religion'. From their mathematics - yes, but how many Nobel laureates or Fields or Einstein or Wolff and the like were Hindus compared to how many Jews? And how many geniuses thought and morality?).
Of course, I would always prefer to identify as a faithful Jew and not as an anti-Semitic (and there is an anti-Semitic circle in Israel, among other things in an anti-religious guise which itself is disguised as a 'rationalist', too often). By the way, the anti-Semitic nations have always lost from their anti-Semitism (from France, England and Ashkenaz during the Crusades and the deportations (they lost people of economics and money) through Ferdinand and Isabella's Spain during the days of the deportation (people of science, thought, economics, money of crucial importance were lost) to the Nazis (they lost the best The human qualities, and the race theory which was an advanced anti-Semitic incarnation - buried Germany in an ocean of disasters and defeats in the end).
I assume that you also prefer to identify as a Jew (or at least come from a Jewish origin - also in the cultural sense) than as a Hindu, etc., despite the excess Hindu quantitative 'survival', for example.
Eddie:
I assume you mean - better than all the other religious memes.
Do not know.
The memes of Hinduism, both older and more common.
It is true that it is difficult to call Hinduism a religion because it is much more sane than all the monotheistic religions.
In any case - the fact that their name is a "good worker" does not say anything about his contribution to humanity but only about his contribution to himself. You should also know that the name anti-Semitism is of the same age as the name Judaism and it is even more common than it and manages to survive even in places where there are no Jews.
Michael Rothschild,
I don't know what supports the concept of the memes, but if so - it gives the impression that the Jewish memes worked better than all the others.
Rotem:
http://en.wikipedia.org/wiki/Meme
https://www.hayadan.org.il/baylor-survey-finds-new-perspectives-on-us-religious-landscape-2109089/#comment-112661
In the hole, what is a meme?
To all those arguing about the Jewish people:
The Jewish people are an example of the evolution of memes (not of genes) and the way they make use - sometimes destructively - of their living environment.
The high intelligence is evidence that without it your chances of surviving as a Jew were slim.
Eliran:
In addition to Ran's correct response - several things:
1. Do you not agree with my claim that if the simulation gives a result that is different from what we see in nature then something is flawed and it does not represent reality in a reliable way? If you accept my argument then there was no point in trying to continue arguing. I would like to remind you that simulations are supposed to simulate the real situation and the better they do it the better.
2. The simulations that are done in physics and cosmology - as well as those that are sometimes done in chemistry and even medicine are conducted simply because it is not possible (for various reasons - ethical, budgetary, energetic or explosive) to conduct the real experiment in the laboratory. In such a case, we assume that the theory we know is correct (and apply it within the simulation) and run the simulation to see the results it gives. This is done for two purposes - one is to create an illustration for processes that we cannot observe and the other is to create predictions of the theory that we do not know how to arrive at in a simple computational way. And why are these predictions used? Even in physics - as in any other field - they are increasingly looking for their mark in reality. If you don't find it, you understand that something is flawed - either in the way the simulation applies the theory - or in the theory itself. Never conclude that something is flawed in reality! Therefore, as I said, since in reality there are clear signs that the existence of sexual reproduction may contribute in certain situations - only four possible conclusions will be planned: either our understanding of the evolution process is incomplete, or the simulation does not reflect our understanding in a reliable way, or our understanding of the conditions that prevailed in my environment Life along evolution is not correct, or the simulation does not reliably reflect our understanding of it. It will never be correct to conclude from it that sexual reproduction does not and did not have an advantage!
Gad,
In principle, you are right - genetic diversity, including that achieved through ethnically 'mixed' pairings, is extremely beneficial.
Your mistake is in relation to the Jewish religion or the Jewish people:
First, Judaism does not prohibit 'mixing' - it is possible for any person of any origin to join the Jewish people in a clear and known way (conversion).
The Jewish people is an excellent proof of the principle of benefit in diversity. It is a fairly mixed people - for several reasons:
1. The fact of dispersing his postcards,
2. The mechanism of absorbing genes through conversion (and there were generations when the conversion process applied to large populations),
3. Adoption of genes by freeing slaves (according to Halacha, a freed slave, of gentile origin, becomes a Jew for all intents and purposes the moment he is freed by a deed of liberation. The process took place in certain generations, and even up to about 400 years ago - a considerable number of people) .
4. Persecutions (which led to acts of rape, or to the wholesale acceptance of Grimm after the murder of men and women, or the murder of men which forced many women to free slaves and marry them).
and other factors.
The result - with relative genetic diversity - and many, many geniuses... as we all know.
Of course, the genetic enrichment process could have led to negative social and national results - since too much absorption of foreign ethnic and cultural elements can collapse cultural and religious archetypes in particular, and destroy the solid foundations of the social order. It didn't happen - because of the intelligent mechanism of the conversion and the religious cultural assimilation that it required.
My opinion is that nowadays we must learn both lessons (not just the first lesson which requires genetic diversity).
Contrary to the Jewish religion, assimilation is a good thing, even for "races"
Because as soon as you preserve the same "race" as it says in the article, bad mutations can accumulate and diseases, after all, we all know what happens to offspring from mating of family members
And as written, assimilation creates offspring with greater genetic diversity, which increases their chances of dealing with changes in the environment, predators and parasites. The second advantage is that shuffling the genes prevents bad mutations from accumulating
Eliran,
A computer simulation will not be accepted as experimental proof in biology. Only a real biological system could satisfy the scientific community, and rightly so.
There is a lot of room for using the computer in the study of evolution, for example to solve equations of population genetics. But the result of a simulation will only be considered a hypothesis until it is tested in reality, or you receive any evidence from biology itself.
Michal, computer simulations are a very powerful research tool, see the sums of money that are spent only in the USA on computer simulations used to simulate nuclear explosions, and the development of new drugs and materials with the help of molecular imaging.
A simple simulation of unisexual or bisexual reproduction can show in principle if there is a distinct advantage to one of the methods, the simulation itself does not have to be too complex or cumbersome but only contain the basic principles of evolution, let it run and check the results.
Eliran:
All you can test in such an exercise is the degree of reliability of the simulation you built.
In nature we have the true result and any simulation that gives a result different from the one observed in nature will probably be wrong.
It is very easy to test this theory with the help of a computer simulation. There are many evolutionary computer simulations in which virtual creatures (bacteria for example) reproduce and go through an evolutionary development process in a virtual living environment. It is very easy to create two groups of creatures, one in which each creature reproduces with itself, and the other in which reproduction is Bisexual - male with female, the simulation can be run thousands of times and unequivocally check if there is a distinct advantage to one of the methods.
Yigal C:
The idea is that when there are conditions that disrupt the accuracy of replication, they will usually damage all the cells of the body and not specifically focus on the sex cells.
Therefore there are many chances that such conditions will result in the animal not reproducing at all even though it has a few sex cells with great potential.
In addition to this - the percentage of germ cells that are expressed is extremely low (this is also related to the rate of reproduction but also to the huge waste of sperm in each fertilization and the fact that most of the source cells for eggs do not become embryos) so the chance that any germ cell will both contain a positive mutation and come to full expression is Absolutely zero.
By the way, one of the interesting creatures in this context is the hydra.
This creature usually reproduces without sex, but takes sex specifically in stressful situations - perhaps to increase genetic diversity.
http://en.wikipedia.org/wiki/Hydra_(genus)
falcon. There is also an example of another multicellular organism that has been multiplying exclusively by asexual reproduction for tens of millions of years. Galileo wrote 3 notices about these animals (department of rotifers):
http://www.ynet.co.il/articles/0,7340,L-3397770,00.html
http://www.ifeel.co.il/page/10499
http://www.ynet.co.il/articles/0,7340,L-3582547,00.html
falcon. There is also an example of another multicellular organism that has been multiplying exclusively by asexual reproduction for tens of millions of years. Galileo wrote 3 notices about these animals (department of rotifers):
https://www.hayadan.org.il/rotifers-multiply-without-sex-3005071/
http://www.ifeel.co.il/page/10499
http://www.ynet.co.il/articles/0,7340,L-3582547,00.html
Yigal, the problem is that even with the mechanism described here, it was only activated on the sex cells. I hypothesize that the value of such a mechanism was negative due to the relatively low rate of reproduction of complex creatures and the energy that must be invested in the above process. While a bacterium "can afford" to produce a thousand harmful mutations as long as one mutation will help it survive in the harsh conditions creatures like humans do not A sufficiently rapid "turnover" of generations or sufficient reproductive potential to effectively use the above mechanism.
My question was about what else and it is at what "level of complexity", if at all, does sexual reproduction become superior to heterosexual reproduction due to its various mechanisms (as in the case of fungi).
From what I understood also with the worms in question, sexual reproduction is secondary to the more common sexual reproduction.
Michael, when you described the analogous situation in complex organisms where changes in genes lead to beneficial or harmful mutations, was it not correct to refer to mutations in sex cells, where only one cell participates in the whole celebration? In short, there may not be a need for a coordinated change of all the cells in the body - it will be derived from the very creation of a multicellular creature from a single cell.
white blood:
Since you don't argue with facts, the answer to your question is that it turns out not always.
falcon:
Bacteria have several mechanisms that complex organisms cannot enjoy.
One is actually a kind of variation on sexual reproduction: bacteria transfer genes between them from time to time and thus increase their survival!
The second is really increasing the rate of mutations in stressful situations.
This is not always about a switch that is activated in stressful situations (apparently this is not usually the case), but rather that in stressful situations the mechanisms that supervise the accuracy of gene copying are damaged and this fact (as long as a minimal level of accuracy is maintained) causes an increase in the rate of evolution (more bacteria die - both because of the stress itself) and they are due to harmful mutations but some of them manage to develop beneficial mutations and adapt to the new situation).
In complex fortifications the situation is much more problematic and this is because the changes in the genome of the various cells - if they apply - cannot be coordinated. After all, someone doesn't sit there and decide at a certain moment to change all the cells of the animal, therefore stress situations that manage to damage the exact replication will damage different cells in different ways.
This means that even if beneficial mutations occur here and there in this or that cell, harmful mutations will occur in other cells at the same time, which will kill the animal.
Different types of cancer, caused by exposure to radiation or carcinogenic substances are an example of what happens to complex organisms when the accuracy of copying their genes is compromised.
All of this is, of course, also connected to the matter of the rate of change of generations that you rightly spoke of.
As far as I know, certain bacteria have mechanisms that allow them to offset (and even be more effective) in dealing with changes in the environment and harmful mutations, and this is by activating a "switch" that leads to a drastic increase in the rate of mutations.
Of course, if a similar mechanism existed in humans (or other creatures with a high vitality and a relatively low reproduction rate) it might have been completely useless.
It is possible that the "efficiency" of bisexual reproduction over heterosexual reproduction is a result of which two parameters?
Two sides of the coin:
The positive qualities might be lost out of this offset, wouldn't they?