Re: Evolution and Sexuality

From: Harnad, Stevan (harnad@aoton.ac.uk)
Date: Mon Mar 06 1995 - 12:13:21 GMT


> From: "Johnson, Richard" <RICH92@psy.soton.ac.uk>
> Date: Mon, 6 Mar 1995 10:43:51 GMT
>
> How concealed is human female estrus really?

To get an idea of the degree to which estrus is concealed in the human,
have a look at the Hamadryas or Gelada baboon's hindquarters during
estrous. We're not talking about subtle cues here: The prominent sexual
swelling is impossible to miss at 50 paces, no matter what species you
belong to!

> Does scent play a part in all of this?

In the case of other species it certainly does, and again, it's no
subtle effect: All the dogs in the neighbourhood congregating in front
of your door when your dog is in heat is ample evidence of this.

So whereas there might be some very subtle pheromonal or other cues
that vary across the human cycle (see the Abstracts below), they hardly
seem comparable with the usual blunderbuss effect of advertised estrous
in other mammals.

> I believe it's the case that females who live together for a long
> enough period (no pun intended) of time synchronise their menstrual
> cycles, and that this synchronisation is mediated by scent.
> If this is so, then some information about the menstrual cycle (if not
> ovulation itself) IS advertised.

It's probable (though not certain) that the synchronisation of human
cycles is mediated by an airborne chemical (though not necessarily one
you can smell consciously).

Here are some interesting abstracts on this topic, but to put them into
context, you should look at the MAGNITUDE of the corresponding effects
in nonhuman species.

Chrs, Stevan

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Grammer, Karl.
5-a-androst-16en-3a-on: A male pheromone? A brief report.
Ethology & Sociobiology, 1993 May, v14 (n3):201-207.

ABSTRACT: In a rating study, 289 women rated the smell of androstenone. The
emotional reaction to androstenone changed during the menstrual cycle.
Subjects rated the main component of male body odor unattractive. This
changed to a neutral emotional response at the conceptive optimum around
ovulation. The finding has direct consequences for hypotheses concerning
the evolutionary loss of estrus. The cyclic-dependent emotional rating of
androstenone might facilitate active female choice of sex partners and may
be a proximate cue for female mate-choice.

Cutler, Winnifred B.; Preti, George; Krieger, Abba; Huggins, George R.; and
others.
Human axillary secretions influence women's menstrual cycles: The role of
donor extract from men.
Hormones & Behavior, 1986 Dec, v20 (n4):463-473.

ABSTRACT: Investigated the effects of axillary extract from 3 human donor males
on menstrual cycle lengths of nulliparous women. Compared to controls
receiving only bland/ethanol applications, 16 women receiving axillary
extracts for 12.5 to 14.5 wks showed a reduced incidence in cycle length
variability and reduced proportion of aberrant length cycles.

Filsinger, Erik E.; Monte, Woodrow C.
Sex history, menstrual cycle, and psychophysical ratings of alpha
androstenone, a possible human sex pheromone.
Journal of Sex Research, 1986 May, v22 (n2):243-248.

ABSTRACT: 76 male and 120 female undergraduates rated 4 odors--alpha
androstenone, methyl anthranilate (a fruity odor), 3-methylindole (a fecal
odor), and exaltolide (musk)--according to strength, familiarity, and
pleasantness. All Subjects indicated the number of sex partners they had
had; females indicated number of days until next menstruation; and males
indicated number of days since last ejaculation. Results indicate that
across odors, the more recently the males had ejaculated, the more
familiar the odors. For females, significant correlations occurred between
number of partners and familiarity/pleasantness of methyl anthranilate.
Lowest olfactory sensitivity in females to androstenone occurred during
ovulation, and menstrual cycle seemed to elicit differences in reactions
to androstenone and skatole. It is suggested that no link between sexual
history and odor perception is justified.

Veith, Jane L.; and others.
Exposure to men influences the occurrence of ovulation in women.
Physiology & Behavior, 1983 Sep, v31 (n3):313-315.

ABSTRACT: Among 29 undergraduate women, those who spent 2 or more nights with
men during a 40-day period exhibited a significantly higher rate of
ovulation than those spending no or 1 night. Cycle length was not affected
by sleeping arrangements, and frequency of sexual intercourse was
unrelated to either cycle length or likelihood of ovulation. The mechanism
underlying this phenomenon may be pheromonal in nature.

Benton, David.
The influence of androstenol--a putative human pheromone--on mood
throughout the menstrual cycle.
Biological Psychology, 1982 Nov-Dec, v15 (n3-4):249-256.

ABSTRACT: Each morning for a month, 18 female undergraduates placed either
5-alpha-16-en-3alpha-ol (androstenol) or a placebo on the upper lip. Each
evening, Subjects rated on 5 scales their moods during that day. In the
middle of their monthly cycle those Subjects exposed to androstenol rather
than a control tended to rate their moods as submissive rather than
aggressive. The compound did not significantly influence ratings of being
happy/depressed, lethargic/lively, sexy/unsexy, or
irritable/good-tempered. Results are discussed in terms of the possible
increased olfactory sensitivity of the human female to androstenol in the
middle of her monthly cycle.

Morris, Naomi M.; Udry, J. Richard.
Pheromonal influences on human sexual behaviour: An experimental search.
Journal of Biosocial Science, 1978 Apr, v10 (n2):147-157.

ABSTRACT: Investigated the effect of a synthetic hypothetical human female
pheromone on sexual behavior. 62 young married couples (mean age of men
25.5 yrs; of women, 24.8 yrs) who were using contraception but not the
pill or the rhythm method were given a set of coded treatments packaged in
one-dose containers, consecutively numbered, and randomized so that each
of 4 treatments appeared twice in 8 days. One treatment was the olfactory
stimulus of interest--6 short-chain aliphatic acids in an alcohol
solution. The other treatments were alcohol alone, water alone, and a
perfume called "heather" in alcohol solution. The treatment was contained
for 3 menstrual months. Results show no effect of the experimental hormone
on occurrence of intercourse, husband's desire for sex, wife's desire for
sex, occurrence of sex play, male orgasm, or female orgasm. Among the 12
couples within the sample who exhibited cyclic sexual behavior patterns of
having sex more frequently at midcycle than during the luteal phase, a
significant difference occurred between the proportion of positive sexual
intercourse reports following exposure to the acid mixture and the
proportion of positive reports following exposure to the other treatments.

Sokolov, Jacque J.; Harris, Ronald T.; Hecker, Michael R.
Isolation of substances from human vaginal secretions previously shown to
be sex attractant pheromones in higher primates.
Archives of Sexual Behavior, 1976 Jul, v5 (n4):269-274.

ABSTRACT: Fractionation of vaginal secretions from 8 19-24 yr old sexually
excited human females (5 were taking oral contraceptives and 3 were not)
by partitioning and chromatographic procedures demonstrated the presence
of short-chain fatty acids which were seen as crucial pheromonal
components in previous higher primate studies. The appearance of these
short-chain fatty acids suggests a possible correlation of the rise and
fall of hormone levels during the female menstrual cycle.

Michael, Richard P.; Bonsall, R. W.; Kutner, M.
Volatile fatty acids, "copulins," in human vaginal secretions.
Psychoneuroendocrinology, 1975 Oct, v1 (n2):153-163.

ABSTRACT: In a double-blind study using a new tampon method, 682 samples of
vaginal secretions were collected from 50 healthy female undergraduates.
Results demonstrate that volatile aliphatic acids are normal physiological
constituents of human vaginal secretions, and that acetic acid
predominates in most women. 30% of the Subjects ("producers") provided
samples containing more than 10 mug of other acids in addition to acetic
acid. The content of volatile acids increased significantly in the 1st
half of the cycle and declined during the 2nd half particularly in
producers. Subjects taking oral contraceptives had lower overall content
of acids and the mid-cycle increase was not observed. Implications for
relationship between vaginal acid levels and sexual activity are noted,
and the finding that the same volatile fatty acids that act as
sex-attractant pheromones in infra-human primates also occur in the
vaginal secretions of normal human females is examined.

Udry, J. Richard; Morris, Naomi M.; Waller, Lynn.
Effect of contraceptive pills on sexual activity in the luteal phase of
the human menstrual cycle.
Archives of Sexual Behavior, 1973 Jun, v2 (n3):205-214.

ABSTRACT: Conducted a double-blind placebo study of the effects of
contraceptives on the sexual activity of 51 18-35 yr. old married women
followed over 3 menstrual cycles. Differences in sexual activity during
the luteal phase of the cycle (days 18-25) were noted. Sexual activity
increased for Subjects on contraceptive pills but not on placebo. The
hypotheses that the difference was due to contraceptive pills directly
affecting the feeling state or overall activity level were rejected. The
data are consistent, however, with the hypothesis that the presence of
endogenous progesterone during natural cycles affects the male so that he
does not desire coitus as frequently during the luteal phase. The absence
of endogenous progesterone during pill cycles removes whatever restraint
progesterone has on coitus. No other interpretation was consistent with
the data. The influence on the human male may operate via a pheromone as
in the case with male rhesus monkeys.

Comfort, A.
Likelihood of human pheromones.
Nature, 1971 Apr, v230 (n5294, 432-433):479.

ABSTRACT: "The likelihood that there are functional human pheromones has been
both asserted and denied, both without direct experimental evidence: the
finding of clear pheromonal effects in monkeys and the recent observation
of menstrual synchronization between close friends reopen the possibility
more definitely, and make direct experiment obligatory. The practical
importance of such research lies in the possibility of primer control over
human endocrine cycles and reproduction generally . . . . Even the study
of simple "releaser" effects could clarify a field of human, and
especially developmental, biology which has been so far suspected rather
than elucidated. Odour fingerprinting techniques and gas chromatography
now make the detection and preparation of human pheromonal agents feasible
if they exist." In a discussion of developmental effects, it is noted
that: "The large observed individual variation in conscious olfactory
awareness is almost certainly in part genetic, but psycho-analytic writers
have both suggested and documented the possibility of a special role for
odour in infant psychosexual development." Also discussed are adult
effects, patterns of response, chemical substances, and models for
effects.



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