At the bottom is her email to me this morning. And directly below is my
reply. Kathy Dettwyler
Dear Dr. Kennedy -- Below is a copy of the email I have sent to the JHE
editors, as well as to a number of colleagues. I am doing everything I can
to see that this paper is not published as currently written. It will not
reflect well on JHE or the discipline because the scholarship is so shoddy.
You do indeed grossly misrepresent my research, and you had to go all the
way back to 1994 to find an edition of Lawrence's book that still mentions
"9 months" as a potential natural weaning age for humans -- because once my
research was published in 1995, Lawrence changed her book in all future
editions to cite my work instead of her previous guesses.
Not to mention that you miscite LAWRENCE as well (something I didn't even
notice yesterday in my outrage about my own work). Her figure of 9 months as
a natural age of weaning is based on the length of gestation being 9 months
in humans. She used to say that in her book, in editions before 1994. What
Lawrence USED to say about multiples of birth weight is that modern babies
triple their birth weight at about 1 year of age, and that therefore 12
months might be a natural age of weaning. She never said that they triple
their birth weight at 9 months, and therefore would be expected to wean at
nine months. Are you not even aware that modern babies do not triple their
birth weight until twelve months???? This can be found in any child care
book available at any bookstore.
As for "early weaning had to start somewhere" -- yes, it started with
changing cultural beliefs and practices. There is no evidence, I repeat, NO
EVIDENCE whatsoever, to suggest that early weaning is biological in nature,
or the result of natural selection. There is abundant evidence to suggest
that, when allowed to nurse as long as they want, most children around the
world will nurse until they 3 to 5 years old, and some much longer.
You write in another email: "The difference must have begun to develop
somewhere, at some time; I
am only proposing a hypothesis for how and when that difference might have
begun. However, as you know, there is an isotopic "weaning signal" in
bone and I am trying to interest colleagues who do that sort of thing."
Indeed, people have already done "that sort of thing." Lori Wright, my
colleague when I was at Texas A&M University, has already done isotopic
research on the "weaning signal" in children's teeth from prehistoric Mayan
samples. This research was prompted following her hiring at A&M where I was
then teaching, and talking to me about early Spanish reports that the Maya
nursed their children routinely until they were 4 years old, and those
Spanish reports being dismissed by most anthropologists as unlikely. See
her publication: Wright, L.E. and H.P. Schwarcz 1999 Correspondence between
stable carbon, oxygen, and nitrogen isotopes in human tooth enamel and
dentine: Infant diets and weaning at Kaminaljuyu. Journal of Archaeological
Science 26: 1159-1170. Her conclusion from this report reads as follows:
"The isotopic composition of Kaminaljuyu´ enamel indicates that many
children continued to drink 18 O-enriched milk between the ages of 2 years
and 6 years, when the premolars were mineralizing. Although solid foods had
been introduced early, before the premolars began mineralizing, breast milk
appears to have provided a significant proportion of liquids imbibed by many
Kaminaljuyu´ children up to the age of 5 or 6 years. This age corresponds
well with the ethnohistoric data for colonial Yucata´ n, where Bishop Diego
de Landa observed that Maya infants were ‘‘weaned’’ at 4 years of age
(Tozzer, 1941). This age also matches Dettwyler’s (1995) calculation that
the ‘‘natural’’ age of weaning for humans falls between 2.5 years and
7.0 years, which she estimates by reference to weaning age and life history
variables among nonhuman primates."
On the topic of the role of meat in allowing "normal" brain growth in human
children -- they need mother's milk, not meat, until their brains have
finished forming at 6-7 years of age. There are several essential
long-chained polyunsaturated fatty acids present in breast milk, including
arachadonic acid and docosahexanoic acid, along with others, which are
absolutely critical for normal human retina and brain development. These
long-chain-PUFAs are not found in animal meat. They are found in the fat of
some marine fish, such as salmon and cod, not likely to be significant parts
of the diet of early hominids. For more information on the nutritional value
of human milk, see De Andraca I, Uauy R: Breastfeeding for optimal mental
development. The Alpha and the Omega in human milk. World Rev Nutr Diet
78:1-27, 1995.
On the role of breastfeeding/breast milk being the difference between life
and death (such that children who still "needed" their mother's milk would
die if the mother was killed while scavenging") -- no one is claiming that
children will die if not breastfed, or not breastfed to a certain age. Most
4 years olds who wean are not instantly at risk of dying. And if they were
at such risk some 2.6 million years ago, early hominid females would likely
do what women have always done, which is nurse other women's babies when it
was necessary due to maternal death.
Obviously, there have been cultural and behavioral changes so that most
human societies no longer nurse all the children until they are 6 years of
age, and most children survive. Some do not, and some survive with impaired
immune systems, and some survive with lower IQs than they would have had if
nursed for 6 years. The fact that mnay individual cultures around the world
do nurse all their children way beyond three, and many more cultures nurse
some children way beyond 3 (as late as 9 years in modern US populations --
see reference below), would seem to suggest that there has been absolutely
no biological change in the duration of normal breastfeeding duration from
the species perspective. Reference: Dettwyler, Katherine A. 2004 When to
Wean: Biological Versus Cultural Perspectives. Clinical Obstetrics and
Gynecology, 47(3):712-723. The existence of this article, in a journal that
might not normally be read by anthropologists, is clearly indicated on my
website, www.kathydettwyler.org.
Speculation about how things "must have happened" and why, in the distant
hominid past, is rampant within paleoanthropology. That doesn't make it
appropriate or likely, nor does it qualify it as science. See for example
my 1988 paper "Can Paleopathology Provide Evidence for Compassion?" in AJPA.
So --- this is what I am upset about. I am cc'ing this communication to the
editors at JHE as well.
Kathy Dettwyler
-----Original Message-----
From: Gail Kennedy [mailto:[log in to unmask]]
Sent: Monday, January 31, 2005 5:01 PM
To: Katherine Dettwyler
Subject: Re: More on JHE article
My goodness - ashamed? How on earth did I misrepresent your research. All
I said was 3 years was not "entirely correct". Isn't this a bit of an
over-reaction? I absolutely did not mis quote Lawrence. Did you check the
edition for that? It varied from time to time. I would like to know what
you are so upset about. Gail Kennedy
At 11:17 AM 1/31/2005 -0500, you wrote:
>Dear Dr. Kennedy,
> I have had a chance to read parts of your JHE article on line.
>Enough
>to prompt me to send an email to the editors asking them not to publish it,
>as you grossly misrepresent my research and also mis-cite Lawrence. You
>really should be ashamed.
>
>Kathy Dettwyler
>
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