[From diet to evolution, prehistoric chompers tell archaeologists
a surprising amount about our ancestors.] [https://portside.org/] 



 Lorraine Boissoneault 
 July 2, 2018

	* [https://portside.org/node/17624/printable/print]

 _ From diet to evolution, prehistoric chompers tell archaeologists a
surprising amount about our ancestors. _ 

 Due to their ubiquity at archaeological sites, teeth are like the
pennies of ancient human remains. But unlike pennies, fossil chompers
can be a treasure trove. , National Geographic Creative / Alamy 


Ten thousand years ago, Mesolithic hunter-gatherers of the Croatian
Peninsula caught fish (perhaps using their teeth to remove the scales)
and foraged for starchy plants. Scientists know this thanks to a
handful of ancient teeth, whose plaque revealed microfossils of fish
scales, fish flesh and starch granules. That calcified bacterial gunk
is helping researchers understand the diet of these
hunter-gatherers—once thought to be a nearly impossible task, since
there are so few human remains from the time period, and foodstuff
doesn’t generally survive in the fossil record.

This finding, published in a recent _Nature 
[https://www.nature.com/articles/s41598-018-26045-9] is just one of
myriad discoveries made possible by the archaeological miracles that
are teeth. Teeth are disproportionately prevalent in archaeological
sites: scientists often find dozens or hundreds for every skeleton or
skull. That’s because the enamel covering a tooth is already 97
percent mineral, and teeth are stronger than bones, so they’re more
likely to survive, writes anthropologist Peter Ungar
in _Evolution’s Bite: A Story of Teeth, Diet, and Human Origins

In other words, teeth are like the pennies of ancient human remains;
they turn up everywhere.

But unlike pennies, they’re often a treasure trove. Everything from
the tooth’s shape to its enamel thickness tells researchers
something about the human whose mouth the tooth once inhabited: what
they ate, where they lived, what diseases they had. As
paleoanthropologist Kristin Krueger
[https://www.luc.edu/anthropology/faculty/drkristinlkrueger/] puts
it, teeth are “little pieces of a puzzle that could help see the
‘big picture’ of someone’s life.”

Krueger assembles those puzzle pieces with the help of a robotic
device called ART, for Artificial Resynthesis Technology
The chewing simulator imitates a human jaw to reveal how noshing on
different foods impact the teeth, looking to see whether those foods
leave tiny abrasions on the machine’s “teeth.” “This has
significant implications in our understanding of hominin diets,
especially those hominis who are thought to consume a large amount of
meat,” Krueger said by email. She and her colleagues have already
discovered that meat doesn’t leave microwear signatures, which could
change how scientists analyze the teeth of hominins believed to be
particularly carnivorous, like Neanderthals

Teeth may seem humble compared to more dazzling specimens like skulls,
but the bony protuberances offer more than their share of surprises.
“I’m constantly amazed by what I find when examining teeth,”
Krueger said. “They truly are little windows into the life of an
individual.” Explore some of the most exciting discoveries made with
the help of ancient chompers, and the technology that’s making these
insights possible.

Taung Child Australopithecus africanus, Australopithecus afarensis and
Homo erectus. The famous Lucy skeleton belongs to the species
Australopithecus afarensis. (Sabena Jane Blackbird / Alamy )


While the marine diet of ancient Croations is exciting news for
scientists, other finds have proven just as spectacular. Take, for
example, the Australopithecine Lucy. Chemical analysis of her teeth
[https://pages.vassar.edu/realarchaeology/2017/02/26/diet-of-australopithecus-afarensis/] shows
that, as far back as 4 million years ago, the diets of hominins
suddenly became much more diversified than other primates. Apes living
in trees were still ordering off the prix-fixe menu of the jungle,
whereas the more human-like hominins had expanded their palate to the
buffet offerings of jungle _and_savannah.

Carbon signatures of the ancient teeth show that Lucy and her kin had
expanded beyond fruits and soft buds of trees and shrubs to actually
eating other animals; the development of thicker enamel
[https://www.tandfonline.com/doi/abs/10.1080/03008200290001032] reflects
that they had also developed more protection to eat seeds, nuts and
roots. “To what extent this dietary shift reflected active hunting,
or the gathering of small prey such as arthropods, or scavenging, or a
combination of all these, is still unclear, but something plainly
happened,” writes paleoanthropologist Ian Tattersall in _The
Strange Case of the Rickety Cossack and Other Cautionary Tales from
Human Evolution

The dental record can also reveal important markers of health to
anthropologists. In one study, researchers looked at dentine—the
tissue that forms beneath enamel—in modern Greek people, compared to
prehistoric Middle Eastern communities. Modern Greeks had levels of
vitamin D deficiency that were four times higher
[https://www.journals.uchicago.edu/doi/full/10.1086/691683] than
their ancient ancestors, perhaps due to spending more time indoors or
changes in clothing, though researchers have yet to find a definitive
answer. Pre-agriculture peoples also had significantly lower rates of
cavities, and researchers have begun extracting bacterial DNA from
calcified plaque
[https://theconversation.com/tooth-be-told-millions-of-years-of-evolutionary-history-mark-those-molars-71428] to
see how strains of bacteria changed after the introduction of farming.

Despite claims made by adherents of the “Paleo Diet” (which, to be
clear, is not reflective of an actual paleolithic diet
not all health outcomes of prehistoric life were positive. Debbie
[https://anthropology.osu.edu/people/guatelli-steinbe.1], an
anthropologist at the Ohio State University and author of _What Teeth
Reveal About Human Evolution
has seen firsthand how disease and malnutrition plagued Neanderthals.
For this she studies linear markings on the enamel called hypoplasias,
which occur when enamel formation stops for a short period due to
genetic causes or environmental ones.

“Some disruptions [in Neanderthals] were quite long, almost up to
three months,” Guatelli-Steinberg says of her research. “It’s
difficult to interpret, but when there’s a long period of time like
that, it might be more likely that it has something to do with

Lower teeth recovered from a cave in Southern China provided evidence
of the earliest unequivocal modern humans in the region. (Liu Wu et
al / Nature)

In 2015, researchers uncovered one of the most significant finds in
dental archaeology: 47 teeth in a cave in southern China
[https://www.nature.com/articles/nature15696]. Identified as belonging
to _Homo sapiens_, these teeth provided evidence that our species
arrived in Asia much earlier than previously thought—as far back as
80 to 120 thousand years ago.

Other researchers have studied the bacteria of ancient plaque
[https://www.tandfonline.com/doi/abs/10.1080/15564894.2017.1382620?journalCode=uica20] to
understand migration among the Polynesian islands, and performed
chemical analysis on teeth looking at strontium isotopes
[http://dro.dur.ac.uk/8514/1/8514.pdf?DDD6+], which come from
groundwater and get locked into the enamel. If the strontium changes
between an individual’s first molar and second one, that suggests
migration from one place to another.

“Another way is to look and see how much variation there is in
females versus males,” Guatelli-Steinberg says. If there’s more
variation in the females than the males, that might mean the females
were migrating from different areas. (How do we know whether the
individual in question is female or male? It turns out that question
can _also_ be answered chemically by testing one of
the enamel-forming proteins

Teeth also offer tantalizing insights into behavior. Krueger, for
example, has examined the wear on Neanderthal teeth to understand how
they used their mouths as an extra tool. “While those individuals
living in more cold and open conditions used their front teeth for
clamping and grasping (most likely using their front teeth as a third
hand during animal hide preparation for clothing or shelter), those in
more wooded and warm environments were occasionally using their teeth
to soften fibers or wood, or perhaps to retouch tools,” Krueger said
by email.

Lower jaw casts of early hominins Paranthropus robustus and
Paranthropus boisei, aka the Nutcracker. (The Natural History Museum
/ Alamy)


Compared to modern humans, many hominins had toothier mouths. The
“Nutcracker,” (aka _Paranthropus boisei
a hominin that lived 2.3 million years ago, had the largest molars and
thickest enamel of any hominin. Homo erectus, which lived all over the
world 1.5 million years ago, had larger canines
[http://australianmuseum.net.au/homo-erectus] than modern humans. But
both still followed the evolutionary trend of generally decreasing
tooth size: The size of our jaw and teeth have slowly been shrinking
over millions of years. Modern humans normally end up with 32 teeth by
the time they’re fully adult, including four wisdom teeth that often
have to be removed because there just isn’t room for them.

“This has largely been attributed to changes in dietary
strategies,” Krueger said. “Why did our dietary strategies change?
They were adaptations to changing environmental conditions that are
well documented during the Plio-Pleistocene.”

Thanks to the huge variations in teeth between modern _Homo
sapiens_ and all its ancestors, teeth are a wonderful tool for
identifying species. But how do scientists know if a particularly
large or small tooth should be classified as a different species, or
is just an example of variation within a species? That was certainly
the question surrounding a single 750,000-year-old molar
[https://www.sciencedirect.com/science/article/pii/S0047248414002814?via%3Dihub] discovered
in 2015. It was the smallest molar ever found in Africa during the
Middle Pleistocene, which increases the amount of variation among all
samples for the region. As to which species it belonged to, that has
yet to be determined.

According to Krueger, there’s no clear-cut answer for these tricky
questions of identification.

“Think about the size difference alone that one can find in living
humans. Think a basketball player versus a horse jockey!” Krueger
said. “All paleoanthropologists agree that variation existed in the
past, but disagree as to the boundary line between variation within
one species versus enough variation to represent a different


Besides jaws that don’t leave enough room for our teeth, another
hallmark of modern humans is our exceedingly long developmental
process, which is reflected in how long it takes us to get a full
mouth of adult pearly whites.

“We have these long childhoods in which we learn and master skills
for our survival, and we seem to have the longest periods of
development of any nonhuman primate,” says Guatelli-Steinberg.
Knowing how long it takes modern humans to outgrow their baby teeth
and gain a complete set of adult molars is useful in looking at the
archaeological record and comparing other species’ development to
our own.

Scientists track this change using a neonatal line that forms on the
first molar at birth—a faint line that’s visible under the
microscope—which Guatelli-Steinberg compares to a birth certificate.
That line is the starting point: from there, scientists can count the
subsequent _perikymata,_ enamel lines that form on a daily basis
like tree rings, to learn how developed a child’s teeth were at the
time of their death. For example, a jawbone with teeth found on
Gibraltar and attributed to a young Neanderthal child was given
the age of three years
[https://onlinelibrary.wiley.com/doi/pdf/10.1002/ajpa.1330700305] at
its death, and showed slightly more accelerated tooth eruption than
in _Homo sapiens_.

Other researchers have used similar methods to argue that development
most similar to that of modern humans began following the emergence
of _Homo erectus_ [https://www.nature.com/articles/414628a].
While_ Erectus_ still had faster tooth development than our species,
they were slower than the hominins that came before.
Guatelli-Steinberg and her colleagues recently submitted a paper on
the dental development of _Homo naledi_ which seems to distinguish
it from other early hominins, and she hopes their work will be just
the beginning of studies into this newly discovered species.

_Lorraine Boissoneault is a contributing writer
to SmithsonianMag.com covering history and archaeology. She has
previously written for The Atlantic, Salon, Nautilus and others. She
is also the author of The Last Voyageurs: Retracing La Salle’s
Journey Across America.
[https://www.amazon.com/Last-Voyageurs-Retracing-Teenagers-Adventure/dp/1605989762/ref=as_li_ss_tl?_encoding=UTF8&qid=1481058563&sr=8-1&linkCode=ll1&tag=smithsonianco-20&linkId=7732040418ea22121ceb3e96e4de982a] Website: http://www.lboissoneault.com/

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