This news release is available in German.
A new study led by evolutionary biologist Alistair Evans of Monash University in Australia, took a fresh look at the teeth of humans and fossil hominins. The research confirms that molars, including 'wisdom teeth' do follow the sizes predicted by what is called 'the inhibitory cascade' – a rule that shows how the size of one tooth affects the size of the tooth next to it. This is important because it indicates that human evolution was a lot simpler than scientists had previously thought. The international team included researchers of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany: The analysis of digital data on fossil hominins generated by the Department of Human Evolution made this large-scale study on dental development possible.
Alistair Evans explains how our fascination with where we come from, and what our fossil ancestors were like, has fuelled our search for new fossils and how we can interpret them. "Teeth can tell us a lot about the lives of our ancestors, and how they evolved over the last 7 million years. What makes modern humans different from our fossil relatives? Palaeontologists have worked for decades to interpret these fossils, and looked for new ways to extract more information from teeth," says Evans.
He then discusses how this new research has challenged the accepted view that there was a lot of variation in how teeth evolved in our closest relatives. "Our new study shows that the pattern is a lot simpler than we first thought – human evolution was much more limited," says Evans. He led an international team of anthropologists and developmental biologists from Finland, USA, UK and Germany, using a new extensive database on fossil hominins and modern humans collected over several decades, as well as high resolution 3D imaging to see inside the fossil teeth.
The team then took the research a step further by applying the findings to two main groups of hominins: the species in the genus Homo (like us and Neanderthals), and australopiths, including specimens like Lucy, the famous fossil hominin from Africa. Evans explains that while it was discovered that both groups follow the inhibitory cascade, they do so slightly differently. "There seems to be a key difference between the two groups of hominins – perhaps one of the things that define our genus, Homo," says Evans.
"What's really exciting is that we can then use this inhibitory cascade rule to help us predict the size of missing fossil teeth. Sometimes we find only a few teeth in a fossil. With our new insight, we can reliably estimate how big the missing teeth were. The early hominin Ardipithecus is a good example – the second milk molar has never been found, but we can now predict how big it was," says Evans, who is also a research associate at Museum Victoria.
The findings of the study will be very useful in interpreting new hominin fossil finds, and looking at what the real drivers of human evolution were. As well as shedding new light on our evolutionary past, this simple rule provides clues about how we may evolve into the future.
Alistair R. Evans, E. Susanne Daly, Kierstin K. Catlett, Kathleen S. Paul, Stephen J. King, Matthew M. Skinner, Hans P. Nesse, Jean-Jacques Hublin, Grant C. Townsend, Gary T. Schwartz and Jukka Jernvall
A simple rule governs the evolution and development of hominin tooth size
Nature, 25 February 2016, published online 24 February 2016
Dr. Jean-Jacques Hublin