Macaque tooth study prompts rethink of human evolution

Date:

Share post:

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.

Macaque tooth study prompts rethink of human evolution
Macroscopic ridges on the outer surface of upper central macaque incisors
[Credit: Ian Towle wt al., 2022]

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.

Macaque tooth study prompts rethink of human evolution
Koshima Island macaques removing and eating limpets
[Credit: Cecile Sarabian/Takafumi Suzumura]

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.”

Source: University of Otago [March 01, 2022]

1 COMMENT

  1. 🙂 Thanks a lot for this.
    It once more proves that H.erectus were no endurance-runners (idiotic hypothesis IMO), but simply followed the coasts as far as Java & later Flores, frequently diving for shellfish etc.:
    -stone tool use = shellfish, cf. sea-otter,
    -brain enlargement: seafood=brainfood (DHA etc.), cf. Pinnipedia & Odontoceti,
    -fossilization in coastal plains, e.g. Mojokerto etc.,
    -shell engravings, Trinil, google "Joordens Munro",
    -pachy-osteo-sclerosis = uniquely seen in show+shallow diving tetrapods (salt water),
    -island colonizations,
    -broad body, flaring ilia, flat feet, big nose, large lungs,
    -platycephaly, platypelloidy, platymeria,
    -etc.etc.
    The evidence is overwhelming:
    it's only a matter of time when the coastal dispersal theory of Homo (vs. apes-australopiths) will be generally accented!
    Google
    "coastal dispersal Pleistocene Homo PPT".

ADVERTISEMENT

spot_img

Related articles

Mystery ‘hobbits’ not humans like us: study

Diminutive humans that died out on an Indonesian island some 15,000 years ago were not Homo sapiens but...

Researchers: Culture drives human evolution more than genetics

In a new study, University of Maine researchers found that culture helps humans adapt to their environment and...

Discovery of microbes with mixed membranes sheds new light on early evolution of life

Current research suggests that more complex life-forms, including humans, evolved from a symbiosis event of Bacteria and another...

Rock art might help understand how human language has evolved

Understanding how early humans developed their capacities of expression which led to emergence of the language which sets...

Identifying major transitions in human cultural evolution

Ten thousand years ago most humans lived in small, kin based, relatively egalitarian groups. Today we live in...

‘Rice theory’ explains north-south China cultural differences

A new cultural psychology study has found that psychological differences between the people of northern and southern China...

Evolutionary changes played a crucial role in industrialization, study finds

A recent study of centuries-old French-Canadian genealogical data by a Brown University economist revealed evidence that supports his...

Researchers reveal ancient Native American thyroid disease using science and art

Art often imitates life, but when University of Cincinnati anthropologist and geologist Kenneth Tankersley investigated a 2000-year-old carved...