Does Testosterone Normally Decrease With Age Or Increase
I've heard that male baldness was caused by increased amounts of testosterone. I've also heard that testosterone levels decrease with age. This doesn't make sense. Does anyone know the answer to this dilemma?
Thank you navigator. However, there is modern data which also indicates that increased levels of testosterone cause baldness. Because of this, drugs which inhibit testosterone production are prescribed to balding men. They have even found in certain male animals that increased levels of testosterone can also cause
Testosterone levels decrease with age, true. As for the relation with baldness, it is not that increased testosterone causes baldness. For those men that will become bald (mainly due to genetics), only a normal level of testosterone is needed to make it happen.
The misconception probably comes from centuries ago when it was noticed that eunuchs and castrati didn't lose their hair. People incorrectly assumed that the reverse was also true, that bald men must be exceptionally virile since losing the balls made guys KEEP their hair.
Once medical science advanced to the point where we knew about testosterone, the misconception also was modernized to incorrectly assume that the cause of baldness was high levels of testosterone. Hope that answers your question
EDIT - adding more in response to your details: The data you speak of is news to me, but interesting. It's still true, though, that for men, in the natural course of things, testosterone levels peak around their mid-20s and decline thereafter.
Video TIL Female Lions Are Attracted to Black Manes - Today I Learned
What Are Some Of The Differences Between Lions With Black Manes And Lions With Blonde Manes
Other than the color itself.
Dark maned lions have higher testosterone levels, are more aggressive and seem to be in better health. This enables them to be the better defender and is a reason for female lions to prefer them.
The darker the mane, the older the lion. It darkens from the back forwards as he ages. Obviously there is some natural variation among individuals too, but generally speaking a black-maned lion is just older than a blond-maned one.
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Why Do Male Lions Have Manes
The lion's mane has long been an iconic symbol, yet there has been no clear answer as to why lion's have manes, or what function they serve. We have spent the last seven years addressing this question using a wide variety of information collected through observations, experiments, and physiological assays such as hormone analyses.
Lions are the only cat with a mane, as well as the only social cat, so it stands to reason that the mane may be related to social behavior. Charles Darwin was the first to suggest that the mane may be a result of "sexual selection" meaning that the mane may play a role in reproductive success. One hypothesis has been that the mane protects a male's neck in fights with other males, and that males that are more successful in fights would then have increased access to females. Another hypothesis is that the mane serves as a signal of male condition allowing males to assess each other's fighting ability and females to choose superior mates.
Our studies addressed both hypotheses. If the mane evolved by conferring protection on male necks, one might predict that the area covered by the mane is a special target of attacks during fights. Additionally, wounds to the neck area might be particularly dangerous. In these cases, there would be significant evolutionary pressure on males to develop protection in the neck area. However, when we examined wounding patterns both in adult males, and in females and sub-adult males (whose neck areas are bare), we could find no evidence that the necks were special targets, nor that wounds to the neck were especially dangerous. These results suggested that the mane's primary function might be to signal male condition.
We tested this idea by using life-sized "model" lions with differing manes. These models were generously donated by Anna Club Plush toys of Holland and were made to exact specifications based on measurements and hair samples from real lions. These models allowed us to observe how real lions responded to variation in male manes. After finding a group of lions, we set up two of the models and fitted them with manes that differed in either mane length or in mane color. We then attracted the lions' attention by broadcasting the sounds of hyenas at a kill (a dinner bell for lions), and watched to see which of the models the real lions chose to approach. The results were startlingly clear: male lions approached shorter and lighter manes, apparently finding them less intimidating. In contrast, females were indifferent to mane length, but they approached dark manes 9/10 times, seeming to find darker manes more attractive.
These findings suggested that the mane is indeed a signal to other lions, but they left several questions unanswered; first, what information does the mane convey? Second, if longer, darker manes are advantageous to males, why don't all male lions have long, dark manes?
To answer the first question, we turned to our long-term records which allowed us to compare the mane color and length of individual males (determined by analyzing photographs) to measures of male fitness including injury, testosterone levels (determined through analysis of blood samples), and offspring survival. Our data confirmed what the model tests had suggested. Males with shorter manes had often been injured or sick suggesting that mane length conveys information about current fighting ability. Males with darker manes were older, had higher testosterone levels, were more likely to recover from injury, spent more time resident with prides, and had higher offspring survival. Thus, mane color appears to convey information about male maturity and experience, testosterone-related aggression, and potential reproductive success.
These answers tell us that the mane conveys important information, but they fail to explain the variability seen in mane length and color. Generally, in studies of sexual selection, such variation is a result of the costs imposed by the sexually selected trait. For example, the male peacock's tail makes him more vulnerable to predation, and males with more exaggerated tails are also more vulnerable. We anticipated a similar situation with lion manes. Using an infrared camera, we measured the surface temperatures of male and female lions, and found that male lions were hotter than females. In addition, males with darker manes were hotter than males with lighter manes. These results suggest that the mane imposes costs in terms of heat stress, and that only superior males can afford to withstand these costs. For inferior males, a dark mane would be a serious handicap such that the costs would outweigh the reproductive benefits.
Ultimately, our research provides good evidence that the mane is a sexually selected signal by which a male advertises his condition to other lions. It also highlights the importance of temperature to lion ecology and behavior and to sexual selection in general. These findings are the subject of a paper in the August 23rd issue of SCIENCE magazine entitled "Sexual Selection, Temperature and the Lion's Mane" by Peyton West and Craig Packer. This paper can be read on line by following the links below.
Full text of Science paper
Lions have manes to attract the females,,,,,It acts as a sexual appeal from male lions to females
Have you noticed that Lions always have those like mullet style Benoni haircuts? Is there a connection? LOL
Lol Cakes just to show off,that they are Malesxxxxx
And they can lazy in the sun and the Females do all the hard work.xxx
Sex Biology Question: Humans Vs Lions
I saw on Youtube once that Lions only mate for a certain period a year (say a few days or a week, I forget) and the rest of the year they are celibate But during this time, they have sex like every 5 minutes Anyway.My question is how come Humans aren't like this? What evolutionary mechanism
I feel like any man who can truly figure out the secret to celibacy could conquer the world. Which is probably why no man has yet. Although my mind is always able to think most clearly after sexual release. It's like all the hormones calm down and some kind of cloud of dust finally settles. At least for the next hour or so.