A conversational strategy used by many vegans is to attempt to disgust the person who is eating animal products by describing what it actually is. That is a fair point that one should be aware of what one eats. I honestly think it’s quite scary how oblivious people generally seem to be about their food. Which is usually exposed when discussing what vegans eat and do not eat with non-vegans. There are several different opinions on which strategy works best and one has to reflect on which strategy works in every given social circumstance. But, please stay to what is true. An egg of a hen is not menstruation or period.
Something about evolution
Both chickens and humans are in the group of amniotes, which is defined by a membrane during the development of the embryo. But then we are separated into synapsida – containing mammals, and diapsida – containing lizards, snakes and birds. Those groups are defined by a certain opening in the skull. The most recent common ancestor between the wild ancestral chicken and humans dates back approximately 320 million years ago (Hedges, Dudley, & Kumar, 2006; “Time Tree,” n.d.). In other words, we are quite different from birds.
Laying eggs
The ovary of the bird usually contains several egg cells that have started to mature. The maturation includes the formation of the yolk and growth of the follicle. When estrogen concentration goes up, proteins from the liver are deposited into the yolk to give it its yellow color. The egg will ovulate and fully mature which includes the formation of the egg white, and shell, but also potential fertilization. The eggs are typically laid until the clutch has been filled, but the interval and timing of egg laying varies between different bird species. A chicken will produce and lay an egg even if it is not fertilized (Sherwood, Klandorf, & Yancey, 2005).
Birds do not have external reproductive organs, instead the have a cloaca from which both eggs and excrements exits. Fertilization occurs when cloacas are joined and sperm is transferred into the female. However, birds are able to save sperms in an internal ‘pouch’, from which the female are able to fertilize eggs for a long period of time after the mating.
Menstruation
In the human ovary, an egg cell is released every ovulation. The ovulation occurs when luteinizing hormone and follicle-stimulating hormone peaks. When the egg cell starts to travel through the fallopian tube, the egg has a potential to be fertilized. During this time, the lining of the uterus starts to thicken to form an endometrium. The fertilized egg will eventually be completely embedded in the endometrium once it has reach the uterus. The endometrium supplies the embryo with oxygen and nutrients, and will later be the place where the placenta is developed (Sherwood et al., 2005). If the egg is not fertilized, humans and a few other animals release the endometrium with the unfertilized egg through the vagina – this is called menstruation or period. Many other mammals do not release the endometrium as humans do, it’s reabsorbed into the body. The latter is typically not referred to as menstruation, but if so, it’s called covert menstruation.
Conclusion
As people seem to be inadequately educated I guess it might sometimes come a legitimate opportunity to inform people what they are eating. But then it’s important to be correct. We all know for example that meat is muscle tissue of animals – that is correct. But, referring to eggs as menstruation is not. Birds have a different reproduction cycle than animals that have menstruation. The similarity is that both the laying of eggs and menstruation is a way of the body to get rid of an unfertilized egg, but in birds the egg is laid regardless if it is fertilised or not, and humans do not lay eggs at all. Additionally, menstruation is specifically defined by the discharge of the endometrium, something that just doesn’t happen in birds.
Apart from being factually wrong, speaking about menstruation with the intent of provoking disgust is problematic. In many parts of human society and history menstruation has been subject to taboo in various ways. And using arguments like that might contribute to that. Menstruation is a completely normal function of the human body and shouldn’t be taboo in any way.
References
Hedges, S. B., Dudley, J., & Kumar, S. (2006). TimeTree: A public knowledge-base of divergence times among organisms. Bioinformatics, 22(23), 2971–2972. doi:10.1093/bioinformatics/btl505
Sherwood, L., Klandorf, H., & Yancey, P. (2005). Animal Physiology: From Genes to Organisms. Thomson /Brooks/Cole. Peter Marshall.
Time Tree. (n.d.). Retrieved January 16, 2016, from http://www.timetree.org/search/pairwise/homo sapiens/red junglefowl
Vegan Biologist 
Thank you for this! Before I was vegan, I was told this as a disgust tactic. As a vegan, I’ve never used it as a disgust tactic because even if it were true, I don’t like disparaging the natural female reproductive system. Btw, the disgust tactic is not what convinced me to become vegan. It didn’t work.
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Eating a fruit is also an act of eating a part of a reproduction system, this time from plants.
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I have no problem with taking parts of a plant (fruit) since plants do not have a developed nervous system like animals do. The animals that we eat have mostly the same neural components as humans. When you steal an egg, you are stealing from the mother, who did not want you to take it, whether or not you think the chicken is happy or not.
To the author of this article, based on a technicality you are right about eggs not being menstruations. However, it is still an excreted product from a chicken. It wouldn’t be wrong to call eggs a chicken period minus the endometrium found in humans. But how many people without a biology background know what an endometrium is? Is eating an excreted chicken product any better than eating meat? I don’t think so except for the fact that the animal didn’t die to produce it necessarily. It doesn’t mean the chicken’s life wasn’t miserable as in many factory farm situations.
Calling eggs a chicken period is not incorrect either and it provides people without the background in biology an analogy to understand what they are eating. In my opinion, that’s fine.
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Hens abandon unfertilized eggs. You’re not stealing anything.
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Also, the fruit of plants are designed to be eaten by animals, that’s why they are bright and attractive, then the seeds are shit out and the plants grow.
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They’re certainly not “designed” to be ground and digested though. So if you’re going to go with what’s “natural”, eating any kind of milled seed or flour is out.
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I don’t see a problem with eating eggs. I keep my own hens free range in my garden. They are happy, healthy and well cared for. I provide them with food, we grow our own (gmo) feed and give them all the kitchen and garden leftovers, clean water, medical care, protection, shelter and the space to roam freely outside. They provide my family with daily fresh eggs which have nutritional value and are a key cooking ingredient in lots of dishes, and they also make lots of manure for the garden. Plus they are colorful and look pretty in the garden, it’s relaxing watching them pecking about. Perfect symbiotic relationship 🙂
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Dear Fiona, do you have male chickens too? Are they happy, healthy too? Or are they dead? That’s the problem with eating eggs.
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I wouldn’t defend eggs as a food as it’s still an excreted product from an animal. Think about other things that are excreted/secreted by animals and decide if it’s still worth it.
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Actually eggs are more accurately ovulation, not menstruation. Ovulation is the release of the egg from the Fallopian tube into the womb. But since unfertilised eggs in the human body still exit along with the menstruation, it is not exactly like what happens with chickens, but I think it’s similar to enough the make the comparison valid.
Whether you want to say you’re eating menstruation or ovulation, it’s not exactly something appetizing.
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Did you even read the post? The whole point is to explain why eggs are not menstruation.
You are very freely requesting others to read books that support your idea, the least you could do is to read a blog post before complaining 🙂 ?
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I’m agreeing with you, it’s not menstruation.:)
Egg release though, is ovulation, which is also isn’t not particularly appetizing.
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Vegans eat abortions… ovaries… even secretions… but do we call it that when WE eat it? No.
We call it bread, cereal, smoothie, berries, fruit, gum, etc.
Why do we only call it by biological terms when it comes from animals? Because sadly, most of us are hypocrites.
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I get the ovaries reference: flowers, tomatoes etc
But could you elaborate on “eat abortions and secretions” ? 🙂
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SCHKORPIO,
Sure, we eat bread, ungerminated (fertile but “aborted”) offspring of grass plants and other nuts and seeds, plus foods like maple, agave, honeydew, etc.
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Of course we eat organic shit all the time, if we didn’t, then where would you get nutrients from? Thin air? Oh wait, I forgot! That’s trees’ leaves’ exhalation (thus being an excretion as well).
Good luck photosynthesizing light I guess!
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It’s not about what we eat, it’s about what we call it. Like I said in my first comment.
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Thank you so much for writing this in such a clear and concise manner. I’m also an animal biologist and a vegan, and I find the ‘chicken periods’ comparison deeply frustrating when talking with other people. I spent two years reading over the research before committing to veganism, and in a world of ‘fake news’ and skeptical readers it’s this kind of accuracy that we all need to be adhering to. Sensationalising animal products to shock people into not eating eggs with inaccurate biology puts every other fact into question.
Hopefully more people will read your article and learn the science. So many vegans get aggressive and angry when they’re schooled on this and I’m getting fed up of being called an ‘apologetic vegan’ for being honest about the science.
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Great post!
I also applaud the final paragraph where it mentions how wrong it is to in fact use the comparison with menstruation to trigger disgust. I would say that is blatant sexism.
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PS – Wouldn’t it be more accurate, IF we are to use a comparison, to say that an egg could be regarded as the “womb”, be it an external one, of the hen?
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