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Science Forum Index » Anthropology - Paleo Forum » Big Idea...
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| arne97... |
 Posted: Sun Jun 08, 2008 4:37 pm |
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The Big Idea
First of all, upfront,you need to know that I am an English major.
Just a BA and that with a C average.
Never took any graduate courses in biology. No Phd or anything
remotely like a "credential" in biology.
One thing I know how to do, like many English majors, is to think
and explain things clearly.
So what I am telling you is as valid as any thesis that comes out
of Harvard's department of biology.
Just because it was thought of by an English major does not mean
it is incorrect.
About 12 years ago I read an article in a mag that said that
bonobos and dolphins are the only mammals, other than humans, who
have sex outside of estrus.
Sex? Estrus?
I did not have any idea what estrus was so I began to haunt the
library at Cornell's veterinary school. I lived close at the time
and
the library was open to anybody; even English majors.
I dug through every paper and text I could find that had anything
to do with estrus. When the Internet came into my life, I learned to
Google and search with the best of them.
So here is what I found and what it means. Speaking modestly,
this is one of the biggest ideas to come down the pike since Newton
and Darwin. Both of them studied theology.
Estrus , or oestrus as the British spell it, is "heat". When a
female cat or mare or female chimp ovulates, they go into heat .
That
means the female becomes sexually excited and will mate with any
male
of her species that is proximate.
No discrimination. No "I have a headache". In chimp land, the boys
stand in line and take turns. Polite.
Gorillas have a different model. The big dominant silverback chases
away rival males so as to keep the estrus female for himself.
Placental mammals are also called "eutherians". We are placental
mammals. We have a placenta . Kangaroos do not.
Placental mammals also have a pelvis which is different from that
of a possom, dinosaur, bird, or frog. We have a "closed pelvis". The
bones come together at the front, at the "pelvic symphysis". It is
like a closed ring of bone, containing the reproductive organs and
the lower intestines.
Keep all this in mind while I tell you more about estrus and
humans.
One definition of humans states that we are a primate that lacks
estrus. This means when women ovulate, they do not go into the crazy
frenzied heat of other eutherians. A woman who is ovulating might
want sex more than at other times in her cycle, but she still can
say "No".
This is important. It means a woman can pick and choose who she
will mate with. This is called "female choice" and is part of
Darwin's explanation of Sexual Selection. He had two brilliant
ideas:
Natural Selection and Sexual Selection. I think Sexual Selection is
much more subtle than natural Selection and that it is a bigger
discovery.
Natural Selection is what weeds out weak traits. Sexual Selection
is where one or the other of the two sexes, chooses a mate based on
some criteria.
Most Sexual Selection is female Choice. In the Galapagos, Darwin
saw finches that varied from island to island. He eventually
realized
that what had happened was that the female finches had chosen, over
the years, male finches which had certain traits that made them more
succesful in particular environments.
Geographic isolation plus female choice equals diversity .
Cottontail rabbits have estrus. Ms Bunny will mate with any male
that hops along. This makes for a lack of diversity. If she does not
choose, all bunnies end up looking alike. A Cottontail from Maine
will look like a Cottontail from Mexico.
If all the dogs in the world were let loose to breed willy nilly,
we would end up with a generic mutt. No St.Bernards and no
chihuahuas.
Women exercise Female Choice. All the variety in appearance of
humans is the result of this. Redheads and blonds exist because
somewhere, women preffered redheaded guys and blond guys. Maybe not
for hair color. Maybe because they were healthier and better mates
than other guys.
So , because women lack estrus, we have diversity in appearance.
Simple straight forward Darwinian Sexual selection. The old guy
puzzled it out all by his lonesome, sitting studying notes on birds
and people.
How then, did we lose estrus?
It happened this way.
200,000 years ago, in Africa, there were bands of H.erectus
homonids. They looked pretty much like us and even their brains were
within the range of modern humans. But they weren't human.
How do we know? Because they had been around for millions of years
and never progessed beyond the hand axe. The hand axe is a sharp
stone that you use to kill antelope or cut up meat.
One of these female H.erectus gave birth to a daughter that was
different. The daughter, when she reached puberty, did not go into
heat when she ovulated. How do we know? Because she was our
ancestor;
Eve. Eve was the first H.sapiens and H.sapiens are primates in which
the female does not have estrus.
How do we know that her mother had estrus?
Because for 150 million years there were eutherians and 99.99% of
eutherians have estrus.
All our close primate relatives have estrus. Women do not.
Now, before I tell what happened that made Eve different from her
mother, let me show the result.
In the H.erectus band, the females went into heat when they
ovulated. A malemerely had to be nearby and he would get lucky. Sex
with females was a sure thing. No male had to come up with candy,
dinner and a ring. he just had to be there when she went into heat.
Not so with Eve.
When she was 12 and first ovulated, she might have felt a bit
randy, but not so much that she would lift her butt for any male.
The
males in the band knew that she was ovulating because they had
really
good noses and could detect an ovulating female.
So they would hang around Eve, waiting for her to go into heat.
But she did not.
During one ovulation one of the guys was sitting patiently,
waiting to get lucky. He would watch her and get bored and scratch
himself and watch her some more. Then this anonymous H.erectus
started making noises. Grunts, humms, whatever.
One particular noise attracted her attention.
Eve looked up.
Serendipitously, he repeated the sound.
Eve smiled.
In that instant, human language was born.
Male vocalization courtship of the female.
This is exactly what happens with birds, which also lack estrus.
The boy bird vocalizes for the female. If she likes what he says,
they form a pair bond. 92% of all bird species form pair bonds. Just
like people.
It turns out that this language thing has implications over and
above the obvious.
Adult birds teach baby birds to sing. They also teach them to use
vocalization to communicate. Baby birds learn to know which sounds
mean "food" and which mean "danger". And it all starts with the boy
courting the girl.
Humans teach infants to vocalize. We teach them to recognize words
and to produce words. We teach them language.
Our brains have two halves, In one half we receive sounds. The
other side produces sounds. Hearing and vocalization.
In the middle sits our consciousness. It exists in the
hippocampus.
Our consciousness sits there sorting through words. We think in
words. When strung together they form thoughts.
Teaching the baby to talk hard wires its plastic brain to make it
more efficient. It thinks better.
Other eutherians have big klunky brains which do not think as
well. They never learned to vocalize information.
Birds think. They have elegant little bird brains. Dinosaurs had
elegant little bird brains. They did not need the big klunky
mammalian type brain . Baby dinosaurs learned to vocalize and their
brains thus became elegant.
H.erectus had 150 million years of klunky mammalian brain because
it needed it to make up for a lack of elegance.
Now, we see how the lack of estrus gave us language AND this
language transformed our klunky mammalian brains into an elegant
human brain.
So where did estrus go?
The loss of estrus resulted from a very small change in the pelvic
floor of the female.
In most eutherians, the female has, in her clitoris, "vestibular
bulbs".
These are small bodies that swell up with blood at ovulation and
put pressure on the "glans clitoridis". In the glans are
encapsulated
nerve endings called "Pathian bodies". They respond to changes in
pressure. They are the same in the male "glans penis" as well as in
the female glans.
When orgasm occurs, the blood pressure in penis and clitoris
spikes. That stimulates the Pathian bodies and gives us the
pleasurable feelings. BTW, Pathian bodies also exist in the palms
of
our hands. Go figure.
The swelling of the vestibular bulbs works just like orgasm,
putting pressure on the glans clitoridis and making the female
sexually excited.
I had thought that the estrus excitement was due to testosterone,
the only homone of desire. But it turns out that the estrus female
has LOWER levels of testosterone than she does at other times in her
fertility cycle.
A woman with a pituitary tumor has scads of testosterone. She
becomes hypersexual but she is still able to say "No".
As near as I can figure, the vestibular bulbs in Eve were
displaced about 5 cm from where they were in her mother.
In Eve, as in other women, these bulbs now reside along the
urethraq, near where it exits the body.
So you are probably wondering why nobody else figured this out. I
believe it is because it involves s-e-x.
Researchers are nervous around sex. They think it is somehow less
than scientific. Look at poor Kinsey!
You can truthfully say that women are sitting on that which made
us human.
Do you think they give the Nobel prize in science to English
majors? |
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