Tooth study prompts rethink of human evolution

Date:
March 2, 2022
Source:
University of Otago
Summary:
A study into tooth wear in a group of wild Japanese macaques has
significant implications for the study of human evolution, a new
study has shown.



FULL STORY ==========================================================================
A study into tooth wear in a group of wild Japanese macaques has
significant implications for the study of human evolution, a University
of Otago study has shown.


==========================================================================
Lead author Dr Ian Towle and Dr Carolina Loch, of the Sir John Walsh
Research Institute, in collaboration with colleagues from Japan, studied
root grooves and large uniform scratches in the macaques' teeth, which
had previously only been described in fossil humans.

"Unusual wear on our fossil ancestors' teeth is thought to be unique
to humans and demonstrates specific types of tool use. These types of
wear have also been considered some of the earliest evidence of cultural
habits for our ancestors," Dr Towle says.

"However, our research suggests this idea may need reconsidering, since
we describe identical tooth wear in a group of wild monkeys that do not
use tools.

"This research raises questions for our understanding of cultural changes during human evolution and suggests we may need to reassess early evidence
of cultural habits." The study, published in the American Journal of Biological Anthropology, concluded the 'toothpick'-like grooves on
back teeth and large uniform scratches on the macaques' front teeth
were actually caused by something more mundane, yet still surprising --
eating shellfish from rocks and accidentally chewing grit and sand with
their food.

This macaque group is well-known for undertaking remarkable behaviours, including washing foods in water, and consuming fish. They have been
studied for more than 70 years and have not been seen using tools or
other items that could cause the unusual tooth wear observed.

Dr Towle has been studying tooth wear and pathologies in a wide variety
of primate species and was "extremely surprised" to find this type of
tooth wear in a group of wild monkeys.

"Up until now, the large scratches in the front teeth of fossil humans
have been considered to be caused by a behaviour called 'stuff and cut',
in which an item such as an animal hide is held between the front teeth
and a stone tool is used for slicing. Similarly, 'toothpick' grooves are thought to be caused by tools being placed between back teeth to remove
food debris or relieve pain.

"Although this does not mean hominins were not placing tools in their
mouths, our study suggests the accidental ingestion of grit and/or
normal food processing behaviours could also be responsible for these
atypical wear patterns." Dr Towle believes the findings provide insight
into how researchers interpret cultural changes through the course of
human evolution.

"We are so used to trying to prove that humans are
unique, that similarities with other primates are
often neglected. Studying living primates today may
offer crucial clues that have been overlooked in the past." ========================================================================== Story Source: Materials provided by University_of_Otago. Note: Content
may be edited for style and length.


========================================================================== Related Multimedia:
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Macaques_and_close-up_of_ridges_on_the_outer_surface_of_upper_central
macaque_incisors ========================================================================== Journal Reference:
1. Ian Towle, Andrew J. J. MacIntosh, Kazuha Hirata, Mugino O. Kubo,
Carolina Loch. Atypical tooth wear found in fossil hominins also
present in a Japanese macaque population. American Journal of
Biological Anthropology, 2022; DOI: 10.1002/ajpa.24500 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220302092729.htm

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