Evolutionary Selection of Testosterone

Discussion in 'Health and medical' started by James Michael H, Mar 14, 2004.

  1. Evolutionary Selection of Testosterone

    Copyright 2004, James Michael Howard, Fayetteville,
    Arkansas, U.S.A.

    It is my hypothesis that mammals evolved because of
    increases in dehydroepiandrosterone (DHEA) (Hormones in
    Mammalian Evolution, Rivista di Biologia / Biology Forum
    2001; 94: 177-184.) I think increased testosterone in
    mammalia produced the primates (Rivista di Biologia /
    Biology Forum 2002; 95: 319-326) which culminated, as a
    result of further increases in testosterone, with humans
    (Androgens in Human Evolution, Rivista di Biologia / Biology
    Forum 2001; 94: 345-362.).

    I suggest estradiol and testosterone direct the use of DHEA.
    That is, target tissues of estradiol and testosterone are
    affected by these two hormones to increase absorption of
    DHEA. My principal hypothesis is that DHEA optimizes
    replication and transcription of DNA. Therefore, DHEA
    affects growth and development and later, maintenance, of
    all tissues. I suggest testosterone increases the use of
    DHEA more than estradiol, therefore, testosterone produces
    more robust growth. Men produce more testosterone than
    women; men grow bigger

    testosterone determines growth and development of tissues
    more robustly than estradiol. This robust growth produced
    the characteristics called "male" from the same primordial
    structures that produce "female."

    Heat increases testosterone formation. (I anticipate your
    reaction here, please wait for the full explanation.) In a
    study of the effects of exercise-induced increases in body
    heat, it was determined that plasma testosterone increases
    33% while sperm counts were not affected (Med Sci Sports
    Exerc 1984; 16: 51-5). I suggest the accident that started
    this selection was connected with the loss of part of one X
    chromosome. This may have produced individuals that
    increased testosterone at the expense of steroids down
    stream. This would have been maximized in mammalia due to
    constant body temperature. This would have produced "male"
    offspring of high testosterone.

    In my work with testosterone in evolution, it has become
    clear to me that excess testosterone is detrimental. For
    example, increased testosterone reduces the immune response
    and wound healing; very negative characteristics.
    Individuals of high testosterone are at a selective
    disadvantage. Therefore, the second "accident" of evolution,
    external gonads, would be selective in reducing excessive
    testosterone levels.

    I am aware that undescended testes produce sterility, that
    is, poor sperm counts. It is my hypothesis that excessive
    testosterone reduces sperm count. This characteristic is
    currently being studied. That is, testosterone is currently
    being considered as a male contraceptive because excess
    testosterone decreases sperm count. Early in evolution,
    those individuals without external gonads would be sterile,
    I suggest as a result of their increased testosterone
    resulting from increased body heat. I suggest evolution
    selected those individuals whose gonads were external
    because of the increased growth and development which,
    eventually produced sperm in greater quantities, among other
    characteristics, and whose testosterone was not so

    I suggest increases in testosterone produced the
    characteristics of maleness as well as those of primates
    and, eventually, humans.