Reason for a Woman's Menstral Cycle?

[Brian]

I have a thought. Over the past several thousand years, homo sapiens have remained genetically indifferent from their ancestors. With a few variations that determine sex and the other various genetic traits that individualize everyone. My thought is that the reason we have remained stagnant in our genetic development is that we are tolerant of our mate's behavioral disorders and most people only have 1 mate for their entire lives. As seen in various primates, 1 male mates with several females, and most groups have new females joining and leaving. This causes the males genes to be spread to more children and the genes of the different females contribute to more mutations thus possibly increasing the rate of evolutionary development.

Now my theory is that nature has a mechanism for this...even in humans. Human females in particular. I think that the female menstrual cycle is nature's way of telling males to move on. The hormonal imbalance spurred on by the onset of the cycle causes the female to be temporarily abrasive. This may tell the male several things. 1 being that if the male has mated recently, and the cycle occurs, it means the act was unsuccessful. Since nature didnt anticipate us having significant medical technology, so it had to give humans a way to know about miscarriages. The second purpose is that after an an egg gets fertilized, a woman skips her menstral cycle and thats how we know that the mating was successful. In my theory, after the baby is born, the continuation of the menstral cycle may signal to the male that it is time to move on to a different mate thus spreading genetic differences. This, as seen in several different species leads to evolutionary growth. But, the only reason we are identical to our ancestors in africa less than 50,000 years ago, is for 1 reason and 1 reason only: Tolerance of our mates. Humans have made medications to bring the effects of the hormonal imbalances of this monthly event down. In a sense, we are making a dead end for our species through another venue.

Now, this is strictly a theory of mine, and its open for any suggestions and/or

constructive critsisms. I am an amaetur so please excuse any mistakes i have made in this post and help me to correct them

[Phi for All]

Why do you see this as stagnation? Perhaps this tolerance led to stonger family bonds and greater learning potential for offspring. This "tolerance" could be why we are as advanced as we are. And medication that mitigates hormonal effects has only been around for a tiny amount of time on an evolutionary scale.

[Brian]

Ahh yes, I see what your saying. But perhaps I was not clear enough on the intent of what mean't by stagnation. I mean't genetic stagnation, how we have virtually been genetically the same as our ancestors. Its hard to tell if all species go through this same trend of genetic non change, but as we've seen with our prehistoric predecessors, the change can sometimes be very rapid.

 

As for your second statement about medications, I did realize that was one of the problems with my thought, and your absolutely right. I appreciate you saying something about that. Im glad that you replyed and gave me some feedback, some help is definitely needed for me to narrow this thought down to a proper theory that may actually make sense (I write with alot of holes).

 

Thanks Phi For All

[Phi for All]

I mean't genetic stagnation, how we have virtually been genetically the same as our ancestors. Its hard to tell if all species go through this same trend of genetic non change, but as we've seen with our prehistoric predecessors, the change can sometimes be very rapid.

I'm no evolution expert, but I do know that change is not required by evolution, it is simply explained by it. If there is no need to change, we simply don't.

 

Look at sharks for example. Amazingly efficient. What would you change? I sure wish I could keep regenerating teeth all my life.

[SkepticLance]

Since we do not know the genetic make-up of our ancestors, I am not sure that we can claim genetic stagnation - at least the way you use the term.

 

However, it is true that our entire species is very genetically homogeneous - little genetic variation. The normal explanation for this is that at one time our species was limited to a relatively few individuals. Indeed, we may almost have gone extinct at one point in time. We are now all descended from a small number of individuals, hence little genetic variability.

 

This makes more sense than your theory.

[mimefan599]

Your theory makes sense in many parts, but one that I have problems with is your reasoning for the male to move on after the birth of the child. If this were true, think of the psychological implications of a father-less generation on the child. Psychology has demonstrated to us the disadvantages of not having a father, so why would that be evolutionarily encouraged?

[Sinombre]

We are now all descended from a small number of individuals, hence little genetic variability.

 

This makes more sense than your theory.

 

Does exists any referred clue of the number of individuals another species descended from?

Like ten turtle eve's?

[Brian]

Sorry its taken so long to respond to any of the suggestions, been kinda busy.

 

Skepticlance, we have some clues of our ancestor's genetic makeup, considering we are their descendants, we can see take what we know about ourselves and apply it to our forerunners.

We do not definitively know that we came from a small number of individuals, simply because there are no records. We can infer from the skeletons of early homo sapiens that there were few...but we've only found a handful of complete tyrannosaurus rex skeletons...doesnt mean that there were only a few. So we cant make the assumption that we descended from a handful of individuals. While this may be the standard explanation for the genetic make up of us, I believe this may be to hasty an explanation. We can't really determine what makes more sense here, because we have no proof that either thing actually happened.

 

 

Mimefan, with psychological affects in mind, we only know the pyschological statistics of a father-less generation from people in our time. If our species had more and more generations without fathers, by this point we would have compensated for the psychological disadvantages.

 

Lastly, Phi for all, you are right that change is not required by evolution, and only explained by it, but we know that species change and evolve, so I would think that the same would apply in my theory.

[michael]

Ahh yes, I see what your saying. But perhaps I was not clear enough on the intent of what mean't by stagnation. I mean't genetic stagnation,

 

I guess you have heard of the Guy who died of PMT??

His wife shot him:-)

 

There have been a number of genetic changes in H. sapiens in the last 10,000 years

 

So we cant make the assumption that we descended from a handful of individuals.

Not true. The Neanderthal genes have been traced back to 1-2 individuals.

We can trace human evolution from Africa from about 100, 000 years ago

[gib65]

Although it is true that men are historically the more promiscuous sex, and therefore have a better chance of mixing their genes with a much wider variety of genes from females, evolution has taken care of the monogamous mating habits of women such that genetic variety is not as much of a problem as you have lead on. Before women commit to a mate, they do a lot of "window shopping" as I like to call it. Women (in my humble experience) tend to be quite promiscuous in the flirting stage, but they eventually make a choice and go with it. What they are doing - or what evolution has done - is making sure the mate they choose has the best genes a girl could ask for, and therefore, proliferating the best in the gene pool.

 

Women tend to change what they see as "sexy" or the "perfect guy" from era to era, and the reason for this is that what passes as a successful man also changes from era to era, due in part to the demands of society and the environment at the time. So women have an instinctual, perhaps unconscious, "tracking mechanism" which tells them what kind of man is successful in the current cultural or environmental climate, and therefore who they find attractive. This allows them to be conservative in their choice of mate when there is no need for change, and when they need to branch out.

[SkepticLance]

Brian said :

 

We do not definitively know that we came from a small number of individuals, simply because there are no records.

 

Sorry Brian. That is not correct. We have the genetic record of mitochondria. Since mitochondria come only from our mothers, we can judge how many women there were in the past by the number of different kinds of mitochondria there are. This is done by evaluating the gene sequences on mitochondrial DNA. A similar result can be achieved for the male line by evaluating DNA sequences in the Y chromosome, which males get from their fathers. Results of these tests show that at one time, the total number of Homo sapiens individuals was very small.

 

Our species is at least 200,000 years old, as shown by fossils of that age. They are clearly different (though the difference is minor) from fossil Homo sapiens of 100,000 years ago. This shows that humans do evolve, over that 100,000 year time period.

To my knowledge, no Homo sapiens fossils older than 200,000 years have been discovered, though, of course, fossils of other Homo species have been found older than that.