Nicolas Noyola
Member
- Joined
- Apr 5, 2018
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- 88
http://anthropogeny.com/Androgens in Human Evolution.htm
I came across this, thought it was rather interesting and sort of related to Peat-y ideas.
"Continued cycling of cold during the upper Pleistocene and changes in containment areas selected for hominids with different ratios of DHEA and testosterone. Some combination of testosterone and DHEA occurred that favored increased use of DHEA for brain growth. A change in the ratio of DHEA and testosterone can slow the onset of puberty and increase anterior brain size. Producing less DHEA reduces the effects of testosterone. Reduced containment (testosterone) or reduced nutrition will slow the pace of puberty. (Increased nutrition should favor those with early puberty.) The percentage of high testosterone individuals would decrease and average size of the forebrain would increase. This began in H. antecessor and H. heidelbergensis. Delayed puberty and increased brain size produced Homo sapiens. Increased brain growth in H. sapiens occurred in the anterior portion of the brain, the prefrontal lobes. This produces the high forehead.
Another shift downward in testosterone levels in a population could occur rapidly. Testosterone compromises the immune system. The effects are especially dangerous when trauma is involved. "Male gender is associated with a dramatically increased risk of major infections following trauma . This effect is most significant following injuries of moderate severity and persists in all age groups." (Offner et al., 1999). "Castration before soft-tissue trauma and hemorrhagic shock maintains normal immune function in male mice, but sham-castrated male mice show significant immunodepression. The maintenance of immune function by androgen deficiency does not seem to be related to changes in the release of corticosterone. We conclude that male sex steroids are involved in the immunodepression observed in after trauma-hemorrhage. Thus, the use of testosterone-blocking agents following trauma-hemorrhage should prevent the depression of immune functions and decrease the susceptibility to sepsis under those conditions." (Wiehmann et al., 1996). These negative effects of testosterone on immunity could increase the probability of infectious epidemics that could radically change the percentage of individuals of higher testosterone in a population. This is very possibly the mechanism involved in extinctions of the robust Australopithecines and various Homo populations.
Once a population is reduced in high testosterone individuals, a stable population could exist for some time. However, due to the influence of testosterone on reproduction, most populations will regain their high levels of testosterone in time. Every positive increase in nutrition would increase the probability of increasing the percentage of high testosterone individuals. Therefore, a "cycling" of high testosterone populations should occur. This may have occurred at the end of the Upper Paleolithic, through the Neolithic, when body size in males and females clearly declined (Frayer, 1984). A reduction in body size indicates that individuals of high testosterone levels in the population died. Body size then increased into the Middle Ages during which epidemics occurred with some frequency. Increased availability of food increases the rate of these cycles, but does not cause them. People of high testosterone simply reproduce faster when more food is available.
Increased amounts of DHEA for relatively lengthy, slower development of the brain results in larger brains in the remaining population. These types of events increase during times of higher population density due to increased nutrition. This phenomenon is identifiable as the decline in body size that occurred from the upper Paleolithic through the Neolithic periods. That is, increased food increases reproduction rates and concentrates high testosterone individuals into population centers. When testosterone reaches supra-optimal levels, infection rates increase. Body size increased in the Middle Ages, which frequently included epidemics. Learning disabilities are "significantly associated" with high testosterone levels (Kirkpatrick et al., 1993). The Renaissance followed the Middle Ages. Populations will periodically cycle through times of increased and reduced percentages of high testosterone individuals. Civilizations evolve in this manner. I suggest the increase in percentage of individuals of higher testosterone produces the "secular trend," in populations. The secular trend is real, identifiable, and vigorous in the U.S.A., at this time (Freedman et al., 2000). "
i've thought about this myself: all things being equal, it seems like high-testosterone individuals are selected for, so why isn't there rapid growth in the proportion of such individuals, especially in today's high-energy environment, with ample calories available? idk maybe if this should go in the political subsection?interesting theory
he has some publications on pubmed as well, all published as an independent researcher
talks about how testosterone likely goes hand-in-hand with the development of the superior intelligence of homo sapiens; humans have higher testosterone than any of the other great apes. More evidence:
“Effect of injection of testosterone derivatives to pregnant rats on the brain of their one-day offspring” B.Y.Ryzhavskii
“Intramuscular injection of Sustanon-250, a drug with testosterone derivatives of various action rate and duration, to rats on day 19 of gestation affected brain development in their offspring. This effect manifested in greater brain weight and neocortex thickness, smaller density of neurons in the developing cortical layer V, and larger size of these neurons and their nuclei and cytoplasm in comparison with control neonatal rats. These data attest to accelerated cerebral development in the offspring of experimental rats in comparison [to] offspring of control rats.”
Bulletin of Experimental Biology and Medicine 2002; 134: 509-11
thoughts welcome
I came across this, thought it was rather interesting and sort of related to Peat-y ideas.
"Continued cycling of cold during the upper Pleistocene and changes in containment areas selected for hominids with different ratios of DHEA and testosterone. Some combination of testosterone and DHEA occurred that favored increased use of DHEA for brain growth. A change in the ratio of DHEA and testosterone can slow the onset of puberty and increase anterior brain size. Producing less DHEA reduces the effects of testosterone. Reduced containment (testosterone) or reduced nutrition will slow the pace of puberty. (Increased nutrition should favor those with early puberty.) The percentage of high testosterone individuals would decrease and average size of the forebrain would increase. This began in H. antecessor and H. heidelbergensis. Delayed puberty and increased brain size produced Homo sapiens. Increased brain growth in H. sapiens occurred in the anterior portion of the brain, the prefrontal lobes. This produces the high forehead.
Another shift downward in testosterone levels in a population could occur rapidly. Testosterone compromises the immune system. The effects are especially dangerous when trauma is involved. "Male gender is associated with a dramatically increased risk of major infections following trauma . This effect is most significant following injuries of moderate severity and persists in all age groups." (Offner et al., 1999). "Castration before soft-tissue trauma and hemorrhagic shock maintains normal immune function in male mice, but sham-castrated male mice show significant immunodepression. The maintenance of immune function by androgen deficiency does not seem to be related to changes in the release of corticosterone. We conclude that male sex steroids are involved in the immunodepression observed in after trauma-hemorrhage. Thus, the use of testosterone-blocking agents following trauma-hemorrhage should prevent the depression of immune functions and decrease the susceptibility to sepsis under those conditions." (Wiehmann et al., 1996). These negative effects of testosterone on immunity could increase the probability of infectious epidemics that could radically change the percentage of individuals of higher testosterone in a population. This is very possibly the mechanism involved in extinctions of the robust Australopithecines and various Homo populations.
Once a population is reduced in high testosterone individuals, a stable population could exist for some time. However, due to the influence of testosterone on reproduction, most populations will regain their high levels of testosterone in time. Every positive increase in nutrition would increase the probability of increasing the percentage of high testosterone individuals. Therefore, a "cycling" of high testosterone populations should occur. This may have occurred at the end of the Upper Paleolithic, through the Neolithic, when body size in males and females clearly declined (Frayer, 1984). A reduction in body size indicates that individuals of high testosterone levels in the population died. Body size then increased into the Middle Ages during which epidemics occurred with some frequency. Increased availability of food increases the rate of these cycles, but does not cause them. People of high testosterone simply reproduce faster when more food is available.
Increased amounts of DHEA for relatively lengthy, slower development of the brain results in larger brains in the remaining population. These types of events increase during times of higher population density due to increased nutrition. This phenomenon is identifiable as the decline in body size that occurred from the upper Paleolithic through the Neolithic periods. That is, increased food increases reproduction rates and concentrates high testosterone individuals into population centers. When testosterone reaches supra-optimal levels, infection rates increase. Body size increased in the Middle Ages, which frequently included epidemics. Learning disabilities are "significantly associated" with high testosterone levels (Kirkpatrick et al., 1993). The Renaissance followed the Middle Ages. Populations will periodically cycle through times of increased and reduced percentages of high testosterone individuals. Civilizations evolve in this manner. I suggest the increase in percentage of individuals of higher testosterone produces the "secular trend," in populations. The secular trend is real, identifiable, and vigorous in the U.S.A., at this time (Freedman et al., 2000). "
i've thought about this myself: all things being equal, it seems like high-testosterone individuals are selected for, so why isn't there rapid growth in the proportion of such individuals, especially in today's high-energy environment, with ample calories available? idk maybe if this should go in the political subsection?interesting theory
he has some publications on pubmed as well, all published as an independent researcher
talks about how testosterone likely goes hand-in-hand with the development of the superior intelligence of homo sapiens; humans have higher testosterone than any of the other great apes. More evidence:
“Effect of injection of testosterone derivatives to pregnant rats on the brain of their one-day offspring” B.Y.Ryzhavskii
“Intramuscular injection of Sustanon-250, a drug with testosterone derivatives of various action rate and duration, to rats on day 19 of gestation affected brain development in their offspring. This effect manifested in greater brain weight and neocortex thickness, smaller density of neurons in the developing cortical layer V, and larger size of these neurons and their nuclei and cytoplasm in comparison with control neonatal rats. These data attest to accelerated cerebral development in the offspring of experimental rats in comparison [to] offspring of control rats.”
Bulletin of Experimental Biology and Medicine 2002; 134: 509-11
thoughts welcome
