Sunday, November 19, 2006

What is a Mammal?

I just heard a piece by Nell Boyce on NPR.  It was great radio and mostly good science. But it wasn’t very good History.  I definitely learned more about mammals.  I was intrigued with the story of the word itself, so interested, in fact, that I listened to the story several times and conducted my own research.  But ultimately, I learned more about how the preeminent naturalist of the 17th Century fails to measure up to 21st Century standards of political correctness than I learned about what science was really like back then or what it is like today.  And in so doing, it probably deceives the reader about what the process of Science is really like more than it enlightens.

Her piece is engaging from the first sentence.  It is a challenge to the listener.  “What is a mammal?” she asks.  It’s hard to resist.  Of course we know what a mammal is.  But then again, it seems too easy.  Maybe it’s a trick.  Maybe we don’t.

The story develops nicely.  First she interviews some people on the street who fall right into the trap.  “Mammals give birth to live young,” someone shouts out.

Nope.  The platypus and echidnas lay eggs but they are mammals.  And some fish and reptiles do give birth to live young, and they are NOT mammals.  “I knew that” I told myself.   Mammals have hair and nurse their young.  I remembered that both birds and mammals were warm blooded.  I figured, “that was that.”  My guard down, I fell right into the next trap.

It is true that only mammals have hair and all mammals have hair.  But only female mammals produce milk.  Boyce made me laugh when she pointed out that most males only manage “little shriveled organs there” and added that male horses, rats and mice have no nipples at all.

Well.  Hmmm….  I guess I never thought about that.  Why “mammals” then?

Now I was thoroughly engaged and right where she wanted me.  I knew that classification systems for living organisms had been used since the Greeks.  Aristotle wondered if a class such as ‘quadrupeds’ existed in reality or only in our minds.  I remembered that Latin names for plants and animals were widely used in Medieval Europe.  But I supposed that the Latin name of the category, ‘Mammalia’ would be attributed to a Swedish naturalist named Linnaeus in the early 1700’s who developed the first comprehensive nomenclature and hierarchical system of classifying all living organisms.

So what was Linnaeus thinking when he decided to name and entire class of creatures on a gland found only in females of the species.  It turns out that there are many other characteristics (most of which were known to Linnaeus) that are shared by all mammals and are unique to mammals.  We have distinctive, three part ear bones; characteristic teeth; a single, lower jaw bone; a neo-cortex; a diaphragm; a four-chambered heart; and specialized, high-powered red blood cells to name a few.  Honestly, it had not occurred to me that Linnaeus had so many alternatives; that makes his choice even stranger.

The answer may be found in 18th Century European society, which was somewhat obsessed with nursing according to Science Historian Londa Schiebinger.  When Linnaeus published his classification of living things in Systema Naturae in 1735, the practice of wet nursing was both commonplace and controversial.  A few years later in 1780, for example, 9 out of 10 Parisian mothers chose not to breast-feed their own children.  This is not just the elite but the middle classes as well.  The pressure on lactating women on surrounding farms to take on more and more children must have been enormous, large enough, in fact, to cause problems with nutrition and disease.  Linnaeus, a physician as well as a scientist, observed the effects of this practice on contemporary children and families and even published a political tract entitled “The Mercenary Wet-Nurses” condemning the practice.

So what does this have to do with the name ‘mammals?’  At roughly the same moment Linnaeus published his first edition of Systema Naturae naming the class. In so doing he used breast-feeding to emphasize the relationships between women, other creatures, and nature as a whole.  So what exactly was Boyce saying?  That Linnaeus picked the name “mammal” to promote breast-feeding?

In fact, Schiebinger concedes that in his critique of wet-nursing he did not mention his term ‘mammalia’ but that “it was written at nearly the same time” and that these things were “on his mind.”  But this was like the fine print in an enormously effective television ad:  the disclaimer had no effect.  I was going along.  I was thinking that Linnaeus must have used Science to further his political and social goals.

Boyce, on a roll, continued.   She let Schiebinger speak: “When Linnaeus connected women to nature and made it seem natural that women, all females, suckle their children, this was the very moment when Western societies decided that women would not be citizens but that they would be compassionate wives, nurturing mothers, in the home.”

In a cheery and uplifting tone this Science reporter leaves the listener with the distinct impression that although “there were other scientists trying to promote alternative terms”, somehow the male-dominated society of Science adopted the Linnaean term not to further the systematic study, organization and naming of life, but instead to repress the progressive women's movement of the 18th Century.

I must admit, I was completely taken by the piece.  It took me several minutes to process.  And afterwards I returned to the story on the NPR website to study what she wrote.  After some research I decided that, although her basic facts were correct and the idea was fascinating, the logic of her argument was flawed and the overall impression that she leaves you with is probably wrong as well.  And it’s wrong in ways that are subtly but profoundly damaging to the integrity of scientific knowledge, scientific methods and the enormous contribution of Linnaeus to modern Biology.

You can read my critique of this story here.

COMMENTS from the original blog

2006-11-29 14:25:18 stefano
Additional resources of interest
Here are some web-based resources of interest for this story.

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