Re: The Evolution of Human Birth

Glenn R. Morton (
Sat, 27 Jun 1998 21:23:41 -0500

At 12:10 PM 6/27/98 -0400, Francis Maloney wrote:
>Jon Krakuer's book Into the Wild gives an interesting account of one man's
>attempt to survive on his own in the wild. The story of the last surviving
>Yashi of the Sierra Nevada is another example that comes to mind of the
>critical need for people to function as part of a social group. The fact
>is human beings depend on complex interactions to survive. To take one
>attribute of human interdependency and make it out to have evolved by
>natural selection isolated from all other social interactions is absurd.

Unless this is the first post of mine that you have read, I don't think
that I have ever tried to isolate a single trait. Both Trevathan and I
would believe that lots of traits (each interacting in various ways)
evolved. But on the other hand, one can not discuss all traits at the same
time or you will have the Library of Congress rather than a short (or long)
post on internet. And Trevathan didn't say that only human birth evolved,
isolated from all other social interactions. If I mis-represented her
excellent book then I am to blame. But if this is not what you mean, then
I am not sure exactly what the point of the above is.

And to emphasize that behaviors are not isolated, Trevathan notes the

"In many non-Western cultures with high infant mortality, few females ever
reach childbearing age in a state of health that enables them to conceive
and carry a fetus to term. In these groups, survival of the mother is of
far greater concern than survival of the child. Afterall, if the newborn
dies, the woman can can have another child within a year, but if the
mother herself dies, it will take many years to replace her. Thus, in many
groups, attention is focused primarily on the mother for the first hour or
so after birth as the attendants make efforts to bring her back to a state
of health as quickly as possible. Often the newborn infant is ignored
during this period of repair, and only when theya re sure that the mother
is stable do the attendants turn their attention to the infant." ~ Wenda R.
Trevathan, Human Birth, (New York: Aldine de Gruyter, 1987), p. 231

> The basic premise of Trevathan's book is that humans have a harder
>time giving unassisted birth than other animals do. This should be
>substantiated by research, that's what makes it science. And if it is
>substantiated that data alone sheds no light on origins.

Why don't you read her book? She did document that fact. While there are
other animals who experience birthing difficulties it appears that chimps
don't and gorillas don't.

>What facts are given here to work with? What is the data that supports the

The size of the infant cranium vs the size of the birth canal and the
relative sizes of these two items in other species. And the data relating
to the length of labor.

Labor length (in minutes)
Stage 1 Stage 2 Stage 3
Sifaka 42 15
Marmoset 30-300 10-30 10-24
Langur 21 4
Colobus 240 20
Guenon 30 30 32
Macaque 23-210 1-2 1-711
Baboon 42-67 4 4
Orangutan 120 30
Gorilla 18-155 1-18 2
Chimp 120 7 8
Human 37-2400 2-385 1-98

Source Table 3.3 Trevathan, Human Birth, p. 97

>1. Breech deliveries occur in 3-4% of all modern human births.
>2. ?
> please fill in the above blank.

That is a cryptic request. I will try. If you lose 3-4% of births to
breech, 1% to shoulder impacting births and then 50% of the children to
disease, you have a less fit population than one that only loses 50% to
disease. It is clear that the latter group will bring more of their
offspring to maturity.

>>Trevathan's thesis is that problems relating to human deliveries produced
>>selective pressures which led to the nearly universal human practice of

>This is a very confusing statement.
>Does this mean we evolved compassion, "the human practice of midwifery", to
>get our big heads, "problems related to human deliveries", through the
>birth canal?

Not necessarily. Have you ever considered that humans were humans even
when they are called Homo erectus? See

for an example of human compassion 1.5+ million years ago among the Homo

>Does the use of the term "selective pressures" imply the development of a
>genetic predisposition to assist deliveries?

While we don't know the entire panoply of genetically influenced behaviors,
we do know of many. The infant will grasp things placed in the hand. That
is genetically controlled. Language development appears to have a genetic
basis. From the Reuters News Agency:

Monday January 26 5:11 PM EST

Researchers Find Gene for Human Speech

By Maggie Fox

WASHINGTON (Reuters) - A family plagued by an inability to make themselves
understood has led to the first proof of
a gene controlling human speech, researchers said on Monday.

Geneticist Anthony Monaco and colleagues at Oxford University in Britain
have named the gene SPEECH1.

"It's definite confirmation and first evidence of a real gene involved in
language development," Monaco said in a telephone interview.
. . .
**end of Reuters report**

Having genetic control over some human behavior is not necessarily bad.

>>Females helping other females birth their offspring, is a
>>human type of care that is only rarely seen in other primates.
>This sounds like feminist ideology talking here. What is the difference to
>the anthropologist between a midwife and a male obstetrician other than sex?

Usually in primitive cultures the men take a dim view of other men helping
their wives give birth. Trevathan relates:

"I found only 22 sources (19 cultures) that show any evidence of the writer
having actually witnessed a delivery. There are several reasons for this,
but the primary one is that strangers, especially men, are rarely welcomed
at such a ritually important and immodest event as birth. Until recently,
most field anthropologists have been men and have had extremely poor luck
pursuing this subject. Raphael, for example relates that one male
anthropologist was killed in the Philippines when he tried secretly to
observe a birth." ~ Wenda R. Trevathan, Human Birth, (New York: Aldine de
Gruyter, 1987), p. 36

>>"At the hominid-pongid divergence, two different adaptive strategies
>>developed that had an effect on parturition. The pongids embarked on a
>>strategy that emphasized increased adult body size, although the selective
>>pressures operating ont hat did not simultaneously favor increases in
>>neonatal size. The result was a large pelvis in a large body, a neonate
>>that was thus relatively small, and easy parturition." ." ~ Wenda R.
>>Trevathan, Human Birth, (New York: Aldine de Gruyter, 1987), p. 22<
>This is conjecture unless the relative adult-neonate sizes have been
>compared over time.

Well, they have. and this is what gets me about us Christians. In general
we don't read the scientific literature enough to know that the questions
we ask have already been answered years ago. As an example the very first
Australopithecine ever found was an infant. We also have Neanderthal
infants and we know the size of the homo erectus birth canal and how big a
head could pass through it.

>>Because of this, apes still give birth with babies facing the mother.
> Perhaps apes recently evolved this feature. It seems that Trevathan
>is building a chain of events to suit her thesis. Wouldn't it have been
>easier for pre-humans to have retained this rather than to develop

You miss the most important thing. Bipedalism places constraints on the
size and shape of the pelvis. We would be unable to walk bipedally with an
ape pelvis (as indeed they are very uncomfortable when they stand upright)
Given the constraints, and the fact that there are no earlier (Miocene)
bipeds, the primitive primate pelvis was that of the chimps not that of Homo.

>>When do we see the 'human' pattern of birth presentation? With the
>>Australopithecines, we at least see a transitional pattern. Some
>>authorities believe that the Australopithecines gave birth with the fetus
>>facing the side, others think they had a human birth pattern. <
> The phrase "some authorities believe" is so overused in evolutionary
>literature it makes me nauseous. Conjecture cannot be used to support a
>thesis, at least not in the scientific method I learned.

I was the one who used that term. Would you prefer me to say "some
authorities have evidence that..." When I slip up from now on, interpret
that phrase in this light.

>>Of course we will never know if they helped each other give birth, but
>they could have used the help.

No, based upon observation of skeletons. All you have presented is your
personal incredulity. Some facts would be nice.
> I always resent being referred to as a species.

OK, there are no species. You and the monkey are one and the same and can
produce fertile offpsring. Happy? :-)

>To place the study of
>human behavior on the same plane as the study of animal behavior is a
>deceptive oversimplification based on a false premise. Mankind's identity
>is not found in its place as an extension of the animal kingdom. This is
>not self elevation it is common sense, for what scientist truly believes
>herself to be equal to an animal? The evolutionist says, in false
>humility, "the rest of the world better realize they are animals". And in
>that very act of definition she proves herself wrong.

Let me quote the Scripture:

Isaiah 29:16 Surely your turning of things upside down shall be esteemed
as the potter's clay: for shall the work say of him that made it, He made
me not? or shall the thing framed say of him that framed it, He had no

Isaiah 45:9 Woe unto him that striveth with his Maker! Let the potsherd
strive with the potsherds of the earth. Shall the clay say to him that
fashioneth it, What makest thou? or thy work, He hath no hands?

Romans 9:20 Nay but, O man, who art thou that repliest against God? Shall
the thing formed say to him that formed it, Why hast thou made me thus?
21 Hath not the potter power over the clay, of the same lump to make one
vessel unto honour, and another unto dishonour?

Those Christians who oppose evolution are exactly in this position,
especially since you can't find a single verse which says

"Animals give rise to animals after their kind" with animals as subject and
animals as object of the sentence. You simply can't find this anywhere in

Evolution does not mean that God didn't create us or isn't in control.

Adam, Apes and Anthropology
Foundation, Fall and Flood
& lots of creation/evolution information