Dental Detectives: Investigating Neanderthals’ food habits using just their teeth

Martin Klapper et al.,Natural products from reconstructed bacterial genomes of the Middle and Upper Paleolithic.Science380,619 624(2023).DOI:10.1126/science.adf5300

Humans have descended from a long line of primates. One well-known human ancestor is the Neanderthal, Homo neanderthalis. Neanderthals lived on the Earth approximately 40,000 years ago, inhabiting modern Eurasia. They are known to have been able to create fire, cook food, weave clothing, make tools, and heal injuries. While these are basic tasks that humans today can perform, these abilities were complex compared to the Neanderthals’ more primitive ancestors. In this study, ancient DNA from Neanderthals’ teeth that contained remnants of natural products they ate at the time were used to find microbes that existed at the same time as them, as they have been lost over thousands of years of evolution. This also provided an insight into the nutritional habits of Neanderthals, as well as natural medicinal products they may have used.

The DNA extracted from the Neanderthals’ teeth is known as a genome. A genome is the complete set of genes present in each cell, and the genes contain information about the organism’s biology. The scientists extracted microscopic bacteria, also known as microbes, found in the Neanderthals’ teeth. This indicates that the microbes were remnants of food organisms eaten by the Neanderthals thousands of years ago. When the organism died, its DNA disintegrated into many small pieces over time as it decomposed, leaving only a few microbes that were preserved in these dental samples. They remained intact because tooth tartar is the only part of a mammal that can fossilise fully.

The DNA from the teeth was used to find biosynthetic gene clusters (BGCs), which are found in the genome. The clusters are tightly-linked sets of genes that do not have any common ancestry. Despite not being related, these genes team up to participate in a metabolic pathway, which is a series of chemical reactions that occurs within a cell to perform a function that is necessary for life. For example, a metabolic pathway is required for simple activities like respiration or excretion. So, once the scientists found the BGCs present in the Neanderthals’ DNA, they got an idea of what kinds of natural products the Neanderthals ate, simply by investigating how each gene in a cluster would play a part in digesting a mystery plant from 40,000 years ago. Isn’t that fascinating?

The research discovered that prehistoric humans ate an unusual number of a plant with bacteria from the genus Chlorobium. For the scientists, this was strange. They say it is ‘a genus not typical of oral microbiota or burial sediments’. It is a genus of green sulphur bacteria, which can photosynthesise in anoxic water: i.e. water that lacks oxygen. Aside from being a rare finding, it was also fascinating for the scientists to see the bacterial remnants so well preserved. Although, there was one challenge. Like all other living things, plants have evolved for millions of years and have decomposed, leaving no remnants. Thus, scientists will probably never know the exact plants that a Neanderthal ate, as those plants simply do not exist anymore on Earth. Still, it is incredibly interesting to see how scientists can be detectives too – solving cases from 40,000 years ago!