It turns out that ground-dwelling birds, such as chickens, which only have remnants of a male sex organ in their adulthood, developed a normal organ at the beginning of the embryonic stage. However, at a later stage of the embryo's development, a genetic program was activated that led to the cessation of embryo development.
In animals that reproduce by internal fertilization, such as mammals (including humans), it seems that from an evolutionary point of view it is impossible to manage without a male genital organ, but in birds the story is completely different. Most male birds do not have a penis and now researchers report in the June 6, 2013 issue of the journal Current Biology that they have discovered why.
bib kiss
It turns out that ground-dwelling birds, such as chickens, which only have remnants of a male sex organ in their adulthood, developed a normal organ at the beginning of the embryonic stage. However, at a later stage of the embryo's development, a genetic program was activated that led to the cessation of embryo development.
"The regulation between cell proliferation and cell death is essential for the control of growth and development," says Martin Kuhn of the Howard Hughes Medical Institute and the University of Florida in Gaysville. "Too much cell division or too little death can lead to uncontrolled growth as happens in cancer. If the balance tilts in the other direction, too little cell division or increased cell death occurs, underdevelopment or the absence of a tissue or organ."
"Our discovery shows that the reduction of the penis during the evolution of birds occurred through the activation of the normal mechanism of programmed cell death, but in a new location - the tips of the developing penis."
The critical gene in the process is called Bmp4. During the development of chickens, Bmp4 is activated and genital development stops. In ducks and their mother, this gene remains switched off and their fins continue to develop.
Given the absence of a penis, chickens and other ground birds have had to develop a method of fertilization that does not rely on penetration. Both roosters and hens have bibs. The reproductive system, the excretory system and the digestive system open into the bib. When the bibs of the male and female touch each other, the sperm is transferred to the female reproductive system. This phenomenon is known as "bib kiss".
It's still not entirely clear why cockroaches and other birds lost their genitalia, says Ana Herrera, the paper's lead researcher. "However, it is possible that the loss actually allows the female hens better control over their reproductive life. The findings may have implications for understanding evolutionary loss more broadly, for example the loss of snake legs. They may also yield answers to medical questions.
"The genitals are among the fastest developing organs in animals, from molluscs to mammals," says Cohn. "It's not just that the genitals are the most affected by birth defects more than any other organ. Discovering the molecular basis for the natural variation created by evolution can lead to the discovery of new mechanisms of embryonic development, some of them unexpected. This will allow us not only to understand how evolution works but also to gain additional insights into possible causes of defects.
to the notice of the researchers
An article on a similar topic on the science website: Nudibranch: A species of androgynous sea snail sheds its penis after each mating but also regrows it
And now the lyrics of the song "Rooster ben Gavr" take on a new meaning
23 תגובות
Let's pretend we replace the word "your nature" with "God" and get a different text, although not so different in your case, but there is a change
That's exactly how evolution works, a mistake in a letter can change a lot
And this happens all the time for millions of years.
To Oren the haughty wise man - you should check your sources again.. there are many studies that have proven and claimed that the appendix is a source of good cells that contribute to the activity of the bowel and even help repair the damage in the intestine after gastronomic diseases,... and now.. furthermore you claim that evolution is not a "mechanism" at all - That's what her claim is, you said it's as random as you say... hmm let's see, first thing - why do birds have wings? Have you ever thought about it? How does "nature" know that in order to float in the air, wings are needed in a pair of aerodynamic rods that will help the bird in flight. Second thing - why do fish have gills? How does nature know that in order for that creature to be able to breathe underwater, a certain organ is needed that will filter the hydrogen and inhale only the oxygen particle.....so you can say according to your method "it's all random" it's a natural choice...the fish evolved and some died because they couldn't breathe And the part that developed a mutation !!random!!!...again random we emphasize the word, they survived and were able to pass the genes to their descendants... how? how? Nature works, what is it all by chance? Molecules just suddenly combine like this with the right conditions for millions of years and know what to do in order to survive? What do they learn from mistakes? ....and if everything is coincidental..then what does that mean about us as mere matter in the universe that will simply become one of them over time and eventually die....or change form for that matter...? Answer me these questions and I will abandon my belief in an intelligent creator (again not the God of the Tanach but an intelligent creator) Thank you, have a good day.
to safkan,
"I wrote why birds do not have prominent genitals. They don't need it, they do well with a small penis. The mating component in most birds is limited, the monogamous family structure and rearing of offspring interests them more than brief mating. The importance given to the size of the penis is a projection on the behavior of the birds from the scale of sexual values of humans, this is a mistaken projection." – safkan
😀 I like your "scientific" approach that the evolution of the birds is due to the moral superiority of the males of the birds over the males of the human race. A stupid idea, albeit a literary one - to let the personification live (something you accuse others of doing), very, very stupid. But most importantly - entertaining!
And regarding evolution - it has no "goal" as you describe it. Have you heard about your appendix? And there are many "dead ends" in evolution. Things that developed but did not benefit in the long term. It's all a matter of random mutation (and not intentional as you imply) that increase the chance of survival/breeding of that species, cause the population of those with the same mutation to increase in future generations of that species and carry it on to future generations.
And one more thing - do you claim that there was a certain male bird who at a certain point decided that he was "fed up" with a life of debauchery and he aspires to find the right "bird" and start a new species of birds that advocates a life of monogamy and strive to remove the mutation that will lead to a smaller and smaller penis? Is this what our sages actually did when they chose to be circumcised? Were they not willing to wait for God to do the desired mutation for them or if they really wanted it (due to moral superiority) would they worry that their limb would get smaller in future generations? An amazing theory that breaks conventions. I would be very happy if you do an article about it.
post Scriptum.
Just now I saw that the article is quite "old" but I read it interestingly, and I responded after seeing the funny and angry response against Nissim who was just trying to contribute.
A question was raised in the title, and no answer was written in the article.
Just a collection of information that has been known for a long time..
A question was raised in the title, and no answer was written in the article.
Just a collection of information that has been known for a long time.
It is likely true, although of course these are insights based on correlations and models and not on controlled experiments...
Is it true that large testicles indicate high sexual competition between the males, or high playfulness/flirtatiousness in the nature of the females? (and which testicles are small in a certain species, indicate the opposite)
Machel
I'm guessing that the size of the goose's penis is because of its body structure: a long body close to the ground that makes sexual contact difficult.
Haim Mazar
I wrote why birds do not have protruding genitals. They don't need it, they do well with a small penis. The mating component in most birds is limited, the monogamous family structure and rearing of offspring interests them more than brief mating. The importance given to the size of the penis is a projection on the behavior of the birds from the scale of sexual values of humans, this is a mistaken projection.
Evolution is a frugal matter, an animal does not develop an organ if it does not benefit from such development. The aerodynamic matter only exaggerates the uselessness, but the uselessness of a large egg-laying organ is the basic figure on which (perhaps) another reduction in the birds will be built (due to the increase of the uselessness from aerodynamic considerations).
The name of the game in evolution is therefore "cost per benefit". To see if you understood this point I will ask you the following question: Why do mammals have a large penis.
I will add Nissim to the list of stupid researchers.
Although he is not a scientist, on the other hand he is a big fool. So that in terms of the balance that includes the element of the scientist that he lacks he has completed by increasing the element of stupidity.
He managed not to understand a number of sentences I wrote that are all clear and the logical connection between them is understandable to those who are able to think.
Nissim thinks that the endless amount of words he utters all the time due to his tendency to prove himself is evidence of understanding. No, chatter is no substitute for understanding.
Some important notes:
If you open a wiki, you will see that there are quite a number of birds with male organs, including a duck with 20 cm (respect!).
In my opinion, the penis can be easily folded in most birds and should not interfere with flight too much.
Regarding monogamy - I learned that there is definitely a connection between monogamy and penis size. A long organ increases the chance of successful fertilization, which is important if you have competitors for the same female. Since 90% of bird species are monogamous, most of them do not need a penis.
And regarding the question "how do they breed" - the male attaches the opening of his bill (the only opening that birds have) to that of the female.
Haim Mazar
An eagle can fly carrying a goat in its wings. What exactly will you learn from your experiment? If the testicles are small then there will be no change. If they are very big then there will be a big change. Isn't it a waste of time in the wind tunnel? 🙂
Haim Mazar
"A model of any bird with external genitalia"... Wow!
there are pictures?? :))) (The comments are almost bursting with laughter. :)))) Except for miracles, of course).
Miracles
Hasids have a long neck. It is possible to perform such an experiment with a stork model. and see what happens
Miracles
If you read carefully what I wrote, you will see that I refer to the experiment. Build a model of a bird and build what happens under controlled conditions. It is possible that my hypothesis will be disproved and on the other hand it may be that it will be recovered. From a research point of view, it is worthwhile to do this. Any conclusion it can open a door to new insights into evolution.
Haim Mazar
In many animals the testicles are internal. The only benefit (that I know of) to external testicles is cooling the sperm cells. That is - the correct question is "why in animal X are the testicles external". And that's what I happened to answer...
Your experiment is a bit problematic - you want to change the structure of the bird by adding external genitalia without changing the structure of the bird beyond that. But - if birds had external genitalia then it is likely that they would have developed in a different way. For example - a longer neck to balance the weight.
I have no idea why another commenter talked about monogamy in birds. This has nothing to do with the size of the genitals. And I certainly have no idea what human experiences have to do with the subject. But when you have an agenda to push you talk a lot of nonsense…..
Roosters may not have sex organs, but they sure do have eggs
The "stupid researchers" - as opposed to the "arrogant commenter who doesn't exactly understand what he's talking about but speaks with complete confidence..."
I actually saw a piglet that did not have any remains of a penis - but what breasts... Aerodynamic it is not!
It may have something to do with the aerodynamic structure of the wings. A prominent addition of a genital organ and external testicles may harm the stability of the winged animals during their flight. A practical possibility to test this is to build a model of any bird with external genitalia and put it in a wind tunnel like those found in the aeronautical industries and see what happens. It is possible that this was said very carefully during
The elution of the winged animals the male genitalia converged into their body.
A chicken is not an example. It is a domesticated animal whose natural reproductive process was castrated among other things. The stupid researchers did not understand this element matter.
Regarding wild birds, "size does not matter". Hidden pins also function when needed. The vast majority of wild birds are monogamous animals that benefit from their participation in the breeding process of the offspring. For them, mating is not a big part of the experience, humans project their experiences onto other animals and then wonder that it doesn't work that way.
To the best of my knowledge, the other vertebrates (except mammals) are not equipped with male genitalia. Reptiles are similar to birds in this respect; No? And with fish and amphibians, fertilization is external anyway.
So how do birds reproduce?