Lost Research Notes Clear Up Racial Bias Debate in Old Skull Size Study
By Anna Groves <> |
October 31, 2018 1:37 pm
[image: skull size debate morton]

A plate from Morton’s 1939 *Crania Americana*. (Credit:

Samuel Morton collected and studied hundreds of human skulls in the early
19th century. By objectively measuring differences in brain size between
people from various societies, Morton believed he had used science to prove
that white people were intellectually superior to other races.

Modern science has long since shown that brain size isn’t necessarily
related to intelligence. Many researchers suspect brain size is instead
tied to things like climate and body size
<>, while
intelligence may be more related to the effciency of the connections
between neurons
<> or the number
of total neurons in the brain

But at the time, Morton and others used his conclusions as a “scientific”
justification for slavery, and he is considered a founding father of
scientific racism.

In recent decades, Morton’s work has been upheld as a model case for how
unconscious bias can creep in to even a careful researcher’s work. Dozens
of scientists have published on the multitude of ways Morton,
unconsciously, demonstrably biased his own results in favor of his

Now, a scientist has rediscovered Morton’s 178-year-old research notes. And
they may force scientists to reexamine how they remember Morton’s work and,
more importantly, the role of bias in the scientific endeavor.
Skulls Measured from Around the World
[image: A hand-drawn skull, lacking its jaw bone, labeled plate nine,
"Peruvian, from the Temple of the Sun, drawn from Nature and on Stone by
John Collins."]

It all started in 1839, when naturalist Morton published a book called
Crania Americana that detailed 158 human skulls he had amassed from across
the Americas. He hoped to use his collection to learn how groups of native
people were related from across the two continents.

Among other details, he listed the internal volume, what he called the
“cranial capacity,” of each of the skulls. To measure this, he (or his
assistant) had filled each skull with white pepper seeds, and then
transferred the seeds into another vessel to find the volume.

Somewhere near the end of *Crania Americana* — almost as an afterthought, a
researcher later would point out — Morton reported the average cranial
capacities of four other races in comparison with the Native Americans.
Caucasian skulls were largest, followed by Mongolian, Malay, Native
American, and finally African skulls.

The following year, he published a full catalog of his collection of
hundreds of skulls from around the world. He then used his personal copy of
the printed 1840 *Catalogue of Skulls* as a research notebook, recording
many of his original seed measurements that had gone into the *Crania
Americana* calculations.

Morton eventually crossed out and replaced some of these numbers, likely
after discovering inconsistencies while remeasuring some skulls. He would
also write some numbers into the front cover of the book, which, based on
the values, we’ll later learn were initial dabblings in a different
measurement technique: replacing the seeds with lead shot.

In 1841, Morton issued a printed announcement to say that lead shot was
much more accurate than seed, and that he’d be switching methods. Then in
1849, he published an updated catalog of skulls, this time with a
shot-based cranial capacity measurement listed for every skull, across all
the races.

Now armed with a greater sample size and more accurate skull measurements,
Morton again presented his results. Caucasians had the largest brains, and
Africans the smallest. This information was misunderstood and widely

It’s safe to say, he’s not considered one of the good guys from science
[image: A 19th-century, black and white painted portrait of Samuel Morton.]

Samuel Morton, a 19th-Century anthropologist whose work on skulls of
different races has been a source of debate for over a century. (Credit:
Wikimedia Commons)
The Mismeasure of Man

Fast forward more than a century. Morton’s work had been largely forgotten
until Stephen Jay Gould, an evolutionary biologist and longtime *Discover*
columnist, published a 1978 *Science* paper titled, “Morton’s ranking of
races by cranial capacity: Unconscious manipulation of data may be a
scientific norm.” In the paper, which he later would develop into the
non-fiction bestseller *The Mismeasure of Man*, Gould outlined a number of
ways in which Morton’s results were biased by unconscious inconsistencies
in the way he carried out his experiments.

The most famous of Gould’s arguments was that Morton, certain that the
African skulls would have smaller brains than the Caucasian skulls,
unconsciously under-filled the black skulls with seeds while tightly
packing the white skulls. Gould’s evidence? When Morton switched from using
seed to the more-accurate lead shot, the average size of the African skulls
increased a lot more than that of the Caucasian skulls.

But Gould didn’t have Morton’s book of handwritten seed-based skull
measurements. No one did. Those data were assumed to be lost to time, so
Gould only had the seed-based averages that were published in *Crania
Americana* to compare with the individual shot-based measurements listed in
the later *Catalogue*.

To complicate things further, Morton’s skull collection itself varied over
time. Many of the skulls measured in 1839 were borrowed, returned to their
owners, and not re-measured with lead shot in 1849. On top of that, new
skulls were added to Morton’s collection before 1849.

In short, it was difficult, if not impossible, to draw solid conclusions
about bias in the seed data without having the actual seed data. And so
Gould’s claims ignited a decades-long debate among researchers about Morton
and Gould’s claims about the skull datasets
<>, their measurements, and the
way both scientists calculated averages based on various subsets of skulls.

The Gould-induced obsession with Morton has never been about proving or
disproving Morton’s racism — that was accepted long ago and especially once
we learned bigger brains don’t mean bigger brainpower. Instead, it has
always been a numbers game, with all sides trying to show, statistically,
how Morton’s racism (or Gould’s anti-racism) affected his scientific
conclusions, despite his efforts to remain objective.

You might think this debate could be easily settled by the skulls. Data
can’t lie. Or can they?
Hidden in Plain Sight

Morton did much of his work at the Philadelphia Academy of Natural
Sciences, where his skull collection and many other archives are still
kept. Paul Wolff Mitchell, a graduate student at the University of
Pennsylvania, was searching through these archives when he came across a
first-edition copy of the 1840 *Catalogue of Skulls* – Morton’s personal
copy with handwritten notes inside.

Mitchell had been working with the skull collection for long enough to
recognize: These notes were the original seed-based measurements assumed to
be lost to time. The missing seed data that would settle the Gould-Morton
debate once and for all.

“It’s amazing what you can find in pretty obvious places when you look for
it,” says Mitchell.

For the first time, Mitchell was able to compare apples to apples to see
whether the African skull measurements increased more from seed to shot
than did the Caucasians or other races, as Gould had claimed.

They didn’t. The seed measurements were equally unreliable for each of the
races. Morton’s infamous unconscious under-filling of skulls of people he
was biased against never happened.
The Good Guys Can Be Biased Too

Mitchell had been investigating Morton in the first place because he was
perplexed by how similar Morton’s work was to that of another researcher,
Friedrich Tiedemann, operating across the world in Germany.

Scientists typically strive to learn something new; to ask a new question
or examine an old question in a new way. But Morton conducted
nearly-identical work to Tiedemann, who published his skull studies in 1836
and 1837.

But rather than hoping to justify slavery and racism, as Morton did,
Tiedemann hoped his measurements would do the opposite. He wanted to
scientifically and objectively demonstrate that the races were equal. And
just as Morton’s conclusions supported his predispositions about race, so
did Tiedemann’s.

“I was especially intrigued that Morton is writing and researching in a
time when someone else of equally high – at least – stature in the
scientific community globally is publishing work that is in many ways, at
least in regard to the data, equivalent to Morton’s,” says Mitchell. “And
he’s coming to radically different conclusions. This to me was a real
[image: A black and white painted portrait of 19th century anthropologist
Friedrich Tiedemann.]

Friedrich Tiedemann, a 19th-century anthropologist who used his scientific
study to make a case for equality of the races. (Credit: Wikimedia Commons)

Once Mitchell learned that the seed measurements couldn’t be blamed for the
disparity in conclusions, he looked elsewhere in their methods.

He found that Morton and Tiedemann had analyzed their remarkably similar
data in two completely different ways. And despite the extreme attention to
detail both seemed to have for whether their volume measurements were
accurate, neither ever documented why they looked at their data the way
they did.

Morton compared averages, while Tiedemann compared the range of data (the
minimum and maximum measurements) for each race. Neither method would come
close to meeting the standards of modern statistical rigor. Neither
scientist provided any reason for choosing the methods they did. Both
scientists found the answer they wanted.

There are many other problems with the two researchers’ work in hindsight.
We’ve learned a lot in the last century about random samples, sample size
and statistics that have added weight to the conclusions we draw from data
in the modern era.

But the bottom line is: Both researchers were equally biased. We just never
paid any attention to the bias from the researcher that agreed with us.

“We might think Tiedemann was a more morally upstanding figure, someone
with whom we can agree more, and his paper rings so much more modern in
some ways than Morton’s does,” says Mitchell. “But he was biased, too.”
Biased Scientists

Nicolaas Rupke is a historian of science and professor of history at
Washington and Lee University. He’s familiar with Mitchell’s work and the
Gould-Morton skull saga, and considers Tiedemann a historical hero.

“In the literature on race and racism, there has been this excessive
emphasis on the racists. And not on the anti-racists. Many people don’t
even realize there were remarkable scientific anti-racists,” says Rupke,
adding, “You know, we pick our heroes from the past according to our own

But Rupke isn’t blind to the bias Tiedemann’s preconceptions introduced
into his science. In fact, he’s seen evidence from throughout history where
this sort of thing happens time and time again.

“I think it is entirely true that you can be factual, totally factual, but
you can get red hot under the collar when people say, *oh, you’re biased*.
And you say, *but here are my facts and I’m honest about them*,” explains
Rupke. “Yet these facts can serve different social-political leanings.”

“When (science is) embedded not so much in technological practical needs
but in value systems that have to do with society, with politics, and all
that, it’s extremely difficult to get clean science,” he says.

As for Mitchell, he thinks the process of modern science will keep us

“Scientists have biases … and the best way we get through them is to not
assume that any individual should ever be free of bias but to expect,
through a communal process, that bias is something that can be at least
minimized if not completely eradicated,” says Mitchell.