Gorilla genome sequenced

[redhen]

There are differences that occur beyond the similarities of a "bleed". Other species have an estrous cycle.

Oh, and now I'm confused, and emailed my prof for clarification. In "human" classes I've taken, menstruation was stated as being unique to humans, that other species have an estrous cycle. But now that I'm looking further (to find a link or two to explain it better and post it here...), I see some references stating that menstruation is also found in the great apes...then another broadens that to include old world monkeys...Now I'm wondering if the "human" classes are more specific about how they define "menstrual cycle" versus "estrous cycle", and the "mammal" classes are a bit fuzzier with the distinctions, and lump things together. I'll let you know tomorrow -- I have my PsyBio of Repro class in the morning.

 

[AquaEyes]

OK, I had some things clarified. Apparently, because of the way information was presented, I misinterpreted some things. In my psych classes, we primarily learn about humans with some biological and behavioral comparisons to well-studied lab species -- typically mice, rats, dogs, etc. When reproductive behavior is described, we learn that, relative to the other species we use for comparison, humans alone have menstrual cycles, while the others have estrous cycles. I took that to mean that only humans have menstrual cycles. In my anthropology classes, the spectrum is more about how humans fit in with other primate species, and so I'd learn about some species' estrous cycles, and other species' menstrual cycles, but why the terms used differed was not discussed. So I emailed my professor for Psychobiology of Reproduction, asking for clarification. See my email and his response below, followed by a concluding summary by me:

From: Christopher Gordon [mailto:[email protected]]
Sent: Thursday, March 08, 2012 11:14 PM
To: Scott Wersinger
Subject: Menstruation

I know it's an odd topic to discuss outside of class, but I'm finding conflicting information regarding whether or not other species menstruate. In some literature, only humans and the great apes menstruate. In others, this is expanded to all old-world primates. Another source includes elephant shrews and a handful of new-world primates. Then others state that humans are unusual in that they shed the lining, that other species re-absorb it. Is this variety of seemingly conflicting information due to different definitions of "menstruation" or "menstrual cycle" that are out there? I'm confused.....

Scott R. Wersinger, Ph.D. [email protected]

7:42 AM (2 hours ago)

to me

Chris,

The definition of menstruation is the shedding of the uterine lining. There is a lot of confusion because many species (e.g. dogs) have vaginal bleeds, which can be confused with menstruation. As you can imagine, it is not trivial (or pleasant) to determine whether the source of the material is uterine or vaginal.

I have a summary of the taxonomic distribution of menstruation somewhere. I will see if I can find it, but don’t hold your breath. I was attempting to determine if menstruation was the ancestral or derived trait. The taxonomic distribution is a mess – it looks like it evolved independently in many species. Of course, I don’t think menstruation the relevant trait – it must have something to do with the evolution of the spiral arterioles.

You kind of have to go species by species. As far as I know, all apes menstruate. (I don’t know of any exceptions, but that may be a limitation of my knowledge.) There are species of old-world primates that menstruate. Some shrew species and some bat species menstruate.

Again, nearly all mammals have hormone cycles. The difference between an estrous cycle and a menstrual cycle is not whether or not hormones cycle, but whether or not the uterine lining is shed.

Does that help?

Scott


So to conclude, the defining distinction between a menstrual cycle and an estrous cycle is that if spiral arteries form in the uterine lining, they will die off and the lining will be shed at the conclusion of the fertile period (this is termed "menstruation"). The spiral arteries function to provide an enhanced uterine lining for implantation of a fertilized egg, but not all species show such a development or shedding of the uterine lining. Those which do not are considered to have an estrous cycle. Species that display a menstrual cycle cluster in some taxonomic groups (humans, the great apes, old world monkeys and possibly other old world primates, some "shrews", some bats) but others display an estrous cycle (canids, felids and other members of Carnivora, ungulates, rodents, etc.).

The main way of determining conclusively which system a species utilizes is by analysis of any discharge that occurs at the conclusion of a fertile period -- if the discharge contains uterine lining material with remnants of spiral arteries, then the cycle is deemed "menstrual." If the discharge is purely vaginal and does not contain remnants of spiral arteries, the cycle is deemed "estrous." Species with estrous cycles may reabsorb -- rather than shed -- their uterine lining, or they may maintain a thickened uterine lining after their first cycle. There are some other subtle differences displayed by individual species, but that is the defining distinction.

 

[EweSheep]

Such interesting topics! I have a few "pick your brain" questions too!

While humans and apes menstrates while other species of animals comes in estrous, is it because the differ between menes and estrus calls for the "readiness" to mate, or to be penetrated by males for them to procreate.

If I can remember right from my vet courses in college, humans, the homo sapies are the ONLY species that would mate at ANY time at any age than the apes and other species which they come into heat to procreate. Humans are known to have sex for pleasure, not by having children alone or any form of "submission" as seen in apes on the National Geo. Women of our species MOSTLY will NOT have sex during menes, probably due to other "traditional" and religious factors "as being dirty or too messy" or some medical reason (unsantitary). It is probable that women at that time are not receptive during menes and while at other time of the month, they would be more willing. Menes does shed the lining of the uterus but also the unfertilized egg as well. In dogs, during heat, her eggs would be waiting for the sperm's arrival. I am not very sure if the eggs would be expelled during that time or closer to the end of their estrus cycle or reabsorbed in the body (uterus).

I know male species are capable of doing the acts BUT only in the female's time of the month. No wonder so many males have fought, triumph or lost their lives in battling the receptive females, and females will outlive a bit longer than males.

I might have more but this one popped in my mind right then and there LOL!

 

[EweSheep]

As for the "grandmother" thesis, I am not sure how many would have survived childbirth. Too many of them died, more so in the 1700 to early 1900 when c-section were so limited and in the infancy stages of medical surgery. Many of the doctors back in those days were not well educated in studying the female antomy (sp) and be able to understand how their body clocks works and menopause was not too common back then. And robbing female corpses for educational studies were not as common either. Many of the women died hitting in 40's and 50's, worn out or died from childbirth or cancer which some of the stories have alot of "stomach ailments" which it could mean bleeding ulcers, stomach, pancereas cancer or cysts or "consumption".

I do agree with infant females have a lifetime of eggs and under continuous development of the ovas (eggs) as she matures. The timing of menes today are usually linked to the foods and environment we live in and we see more and more women starting much earlier than 12 years old. Back in those days, it was unheard of and many of them worked on farms or hard labor in factories and menes would be delayed as long as two to three years. (as I read it somewhere on internet on Civil War era ladies).

 

[AquaEyes]

Such interesting topics! I have a few "pick your brain" questions too!

While humans and apes menstrates while other species of animals comes in estrous, is it because the differ between menes and estrus calls for the "readiness" to mate, or to be penetrated by males for them to procreate.

If I can remember right from my vet courses in college, humans, the homo sapies are the ONLY species that would mate at ANY time at any age than the apes and other species which they come into heat to procreate. Humans are known to have sex for pleasure, not by having children alone or any form of "submission" as seen in apes on the National Geo. Women of our species MOSTLY will NOT have sex during menes, probably due to other "traditional" and religious factors "as being dirty or too messy" or some medical reason (unsantitary). It is probable that women at that time are not receptive during menes and while at other time of the month, they would be more willing. Menes does shed the lining of the uterus but also the unfertilized egg as well. In dogs, during heat, her eggs would be waiting for the sperm's arrival. I am not very sure if the eggs would be expelled during that time or closer to the end of their estrus cycle or reabsorbed in the body (uterus).

I know male species are capable of doing the acts BUT only in the female's time of the month. No wonder so many males have fought, triumph or lost their lives in battling the receptive females, and females will outlive a bit longer than males.

I might have more but this one popped in my mind right then and there LOL!

Based on what I've been learning, no one has come up with a "reason" for menstruation. In other words, there is no (thus far) known clear advantage to a species having a menstrual cycle or estrous cycle.

Humans do "mate" outside of reproductively fertile times for females, and it is unusual, but it's not completely unique. Among chimps, there is indeed a higher amount of activity during the fertile time, but still some outside that time. And Bonobos "do it" several times a day, in all sorts of combinations (yes...all sorts). Other species engage in activity that is related to sex but might not be "complete" in its sequence -- read into that as you wish. Again, such activity increases during "mating season" but might not be unknown at other points.

And some males engage in "activity" not only when females are "in season" but when they, themselves are "in season." In other words, not all males of species are "ready to go at any moment." Sometimes, "getting in season" requires only the detection of a female "in season" and a short amount of time, but in these instances, measurable surges in hormones can be detected that differ significantly from the levels present prior to introduction. In other species, the "getting ready" period for males takes longer. Take deer, for example. If you brought an out-of-season male (say, from the southern hemisphere) and released him into a herd of in-season females, he probably won't "get going" right away. Or, males may engage in the behavior but be incapable of producing sperm when "out of season." In these situations, a stimulus is required to initiate behavior seeking the reward of pleasure derived from the mating act, but the sperm production requires more time to "kick in."

There is such variety among all the species that it's difficult to say "this is the way things work" in many areas.

 

[EweSheep]

Sometimes animals will not mate in readiness if environmental plays a factor. Starvation, unacceptable surroundings (winter) or the mates themselves (like horses, one stallion will not breed grey mares but will mate with other colored mares) or amount of distances (like the elephant herd, you will not find a breeding male in the family but only teenagers/juvies). And I believe human males probably most likely would follow that pattern as well. You don't see any pregancies or mating going on in the concentration camps of WWII (I have not found documentations regarding to this matter yet).

 

[AquaEyes]

Sometimes animals will not mate in readiness if environmental plays a factor. Starvation, unacceptable surroundings (winter) or the mates themselves (like horses, one stallion will not breed grey mares but will mate with other colored mares) or amount of distances (like the elephant herd, you will not find a breeding male in the family but only teenagers/juvies). And I believe human males probably most likely would follow that pattern as well. You don't see any pregancies or mating going on in the concentration camps of WWII (I have not found documentations regarding to this matter yet).

Yes, environmental cues and physical condition may inhibit the mating behaviors by means of restricting production of hormones required to initiate them. Women, for example, stop their menstrual cycles if their body fat percentage falls too low. I think (can't remember for sure) that hormones produced by fat cells either facilitate by presence or inhibit by absence the initiation of the sex hormone cycle in the hypothalamus. In any case, when the number of fat cells is too low, the sex hormone cycle stops.

The camps had people separated by sex -- males kept together in one prison, females in another. Sometimes both prisons were on the same grounds, but the populations were fenced off from each other. Yet another horrible example of what people are capable of doing to other people.

 

[Matthew3590]

I was told by my biology teacher that the main reason starvation can limit mating is because the animals do not have the energy for it. Unless that is what you just said but in a different way.

 

[EweSheep]

If they tried to attempt to mate while starvation, the mothers would not even get pregnant or carry an embryo full term.

 

[redhen]

Thanks for all the great info, Aqua!