The analysis of prehistoric wisdom teeth has given scientists more insight into human evolution, explaining patterns in which dentition develops nowadays.
The findings were featured in the journal Nature, on Thursday, February 25, and stemmed from research presided over by Alistar Evans, affiliated with the School of Biological Sciences, at Monash University in Australia.
The purpose was to examine prehistoric wisdom teeth in order to understand why their modern-day counterparts have such diminutive proportions.
Among bygone hominin species, wisdom teeth used to be quite sizable, with occlusal surfaces that enabled chewing being between 2 and 4 times bigger than those pertaining to modern humans.
In fact, wisdom teeth nowadays are not just dwarfed by other molars, but sometimes they fail to erupt altogether.
Prior studies had indicated that prehistoric wisdom teeth started to grow smaller as humans switched to different diets, as cooking evolved, making it unnecessary for dentition to be so well-developed and for jaw muscles to be so robust and powerful.
Now however, it has been proven that this shrinking process started much earlier than previously thought. The discovery was made by looking at prehistoric wisdom teeth belonging to our hominin ancestors and comparing the size of these molars with that of modern-day wisdom teeth.
It was soon noticed that there are 2 main types of hominin teeth: those corresponding to predecessors of the genus Homo (such as Australopithecus, who were the first bipedal hominids), and those associated with species from the genus Homo (such as Homo Sapiens, a species that includes modern humans).
Among australopiths and other related species, teeth appeared to grow in size towards the rear of the mouth, by rates that remained relatively constant no matter how large dentition was.
In contrast, among hominids from the human genus, the pattern was the opposite, with wisdom teeth getting smaller than their neighboring molars.
As researchers explain, it may be that these disparities emerged as our predecessors from the genus Homo mastered tools, which allowed them to slice, crush and dice food more easily than ever, without having to rely so much on their prehistoric wisdom teeth.
Study authors are also arguing now that Homo habilis shouldn’t be considered as the earliest specimen representing to the genus Homo after all, given the fact that its dentition shows the same patterns as the ones encountered among several australopithecine species.
As a result, it may be more accurate to refer to these extinct hominids (nicknamed “nutcracker men” because of their disproportionately large chewing teeth) as Australopithecus habilis, instead of Homo habilis.
Researchers have also come up with an explanation for the fact that prehistoric wisdom teeth follow clear patterns of evolution, instead of displaying significant variation.
It all comes down to the fact that ancient hominins and modern-day ones are mammals, so the size of their dentition is regulated by a commonly encountered mechanism known as “inhibitory cascade model”.
Basically, teeth that emerge earlier influence the dimensions of those that erupt at a later date, and one particular molar can dictate the size of the one next to it.
This means that even incomplete tooth fossils, such as the ones belonging to Ardipithecus, can provide scientists with enough information in order to predict and reconstruct the entire dentition corresponding to that prehistoric hominid species.
Now, study authors are planning to devote more of their energy to examining Homo naledi remains that were recently brought to light in South Africa.
Allegedly, this species has features reminiscent of the Homo genus, but also other traits that are characteristic of australopiths, so it will be intriguing to discover what category their prehistoric wisdom teeth fall into.
It is hoped that by probing into this less explored area of research it will be possible to find out more about how evolution has unfolded over the past 7 million years, ever since humans diverged from chimpanzees and other primates.
Image Source: Lawnchair Anthropology