A burial monument in the northern hills of Spain, seemingly reduced to ruins, appeared unwilling to yield the secrets of those buried within. Yet, using innovative techniques, VUB researcher Jacob Griffith and his colleagues managed to uncover details about the way of life of a prehistoric tribe from the era when our ancestors were first beginning to experiment with agriculture. More than 2,200 years later, modern scientists have unravelled their story using cutting-edge isotope analysis. Today’s archaeology is more reliant than ever on hard science, bringing our ancestors vividly back to life. Bioarchaeologist Jacob Griffith can picture the people of this ancient settlement in great detail. “They were breastfed for a shorter period than other tribes in the region,” he explains.
First, tell us a little about yourself—how did you find your way into bioarchaeology?
“My family is from Cornwall, in the far south of the UK. My grandfather was absolutely fascinated by stone circles and ancient monuments. Nearly every weekend, he and my mother would take us on archaeological excursions. Those trips not only sparked a deep interest in the past but also instilled in me a love for nature and animals. In the end, the choice was simple: I was either going to study zoology or become an archaeologist.
At eighteen, I started studying archaeology at Cardiff University. One day, the head of the department asked me, ‘What do you want to do in the future?’ I told her that I loved studying people and animals, but that archaeology also fascinated me. She understood exactly what I meant and said, ‘I’m a bioarchaeologist. I study both. Maybe that could be something for you?’ That was a real eye-opener.
After Covid, I wanted to do a PhD, and Belgium turned out to be the ideal place—especially with the research being done at the Brussels Bioarchaeology Lab, led by Professor Christophe Snoeck at the VUB. I started my doctorate and secured an FWO grant. While my bachelor’s and master’s studies focused mainly on animals, I now use isotope analysis to study humans. My research is centred on the transition from the Mesolithic to the Neolithic—the period when people first began to practise agriculture.”
De publicatie gaat over een stam in de heuvels van Álava in Baskenland. Ben je daar zelf geweest?
“Misschien verrassend, maar nee, ik ben er nooit geweest. De menselijke resten – tanden en botten - zijn naar België gebracht, en hier heb ik ze onderzocht. We hadden alles wat we nodig hadden. De site zelf is zwaar beschadigd door landbouw en eerdere menselijke activiteiten. In 1925 werd er al gegraven door een antiquair – of een vroege archeoloog – die de site overhoop haalde. Waar je bij archeologische opgravingen normaal nog een bepaalde structuur ziet, was hier bijna alles vernietigd. Daarom koos ik voor een forensische en zo wetenschappelijk mogelijke aanpak. Ik wilde zoveel mogelijk over deze mensen te weten komen, omdat hun begraafplaats door de geschiedenis is weggevaagd, en daarmee een groot deel van hun leven verloren is gegaan. Dat was de grootste uitdaging.
Toch zou ik er graag eens naartoe gaan, gewoon om de plek zelf te zien. Het is een bescheiden verhoging in het landschap, een heuveltje waarin mensen begraven lagen.”
What Did Your Research Reveal About the People Buried There? What Was Their Life Like?
“There were at least 25 individuals buried in the grave, of whom we examined 18. They lived in the hills. Previous studies had already looked at the people who lived in the valley, about a kilometre south of the site. The highland inhabitants lived during a period of major change. The population was growing rapidly—partly due to natural increase and partly through migration. At the same time, farming techniques were improving, society was becoming more complex, and people were beginning to experiment with metalworking—not bronze, but copper.
"What we discovered was striking: almost all of the individuals at this site showed little to no mobility"
But something unusual was going on. Earlier excavations in the region had revealed different burial traditions: some individuals were buried in caves, while others were laid to rest in large tombs. This seemed to be more than just a difference in custom—it suggested the existence of two distinct groups.
Our colleague Teresa Fernández Crespo examined the human remains and found that these groups not only had different burial practices but also led different lifestyles. The prevailing theory was that Álava was home to two major communities, living in separate locations and following different traditions.
We initially assumed that the burial site we were studying was simply a variation of the valley dwellers’ customs—the only apparent difference being that these people lived on a hill rather than in the valley. But isotope analysis revealed a surprising twist: this group had a lifestyle distinct from both the valley inhabitants and those buried in caves. In other words, there weren’t just two communities—there were three.”
Were You Able to Trace Their Origins?
“Yes, and what we found was remarkable: almost all of the individuals at this site showed little to no mobility. This suggests they likely spent their entire lives in the same region, where they were eventually buried.
Except for one person. There was a single individual—the only one we could identify as female—who stood out completely in the data. Her isotope values were different, indicating that she hadn’t grown up in this region. Isotope analysis also revealed that her diet was different and that she had been breastfed for a longer period than the others. This suggests she came from another community, with different eating habits and possibly a different social structure.
However, it’s important not to generalise this finding to all women. We’re talking about a single individual, and the fact that she was female doesn’t necessarily mean much on its own. From this site, we were only able to determine the sex of three individuals.”
You Even Discovered How Long They Were Breastfed?
“We used a new technique developed by my co-author, Teresa Fernández Crespo. By taking tiny samples from the first permanent molar, we were able to determine the duration of breastfeeding. Teeth grow in layers, much like tree rings, and store isotopes that reveal dietary patterns. High nitrogen levels indicate breastfeeding, and when those levels drop, we see the transition to solid food.
What stood out was that children here were breastfed for a much shorter period—typically one to two years—whereas in the valley, it was three to four years. This could indicate a different lifestyle or parenting approach. We can also determine what solid foods they ate afterward. For instance, meat from land animals creates a different pattern than fish, which raises nitrogen levels. Step by step, we can reconstruct an individual’s diet.”
"They too made choices, adapted, and lived their lives just as we do"
Why Do You Think They Were Breastfed for a Shorter Time?
“We can’t say for certain, but we do know that breastfeeding is influenced by various societal factors. In this case, the environment seems to have played a key role. Because they lived on a hill rather than in the valley, they likely had access to different natural resources. It’s possible that some foods were less available, prompting mothers to introduce solid food earlier.”
Food Must Have Been Central to Their Way of Life. What Did They Eat?
“What we can say with certainty is that they didn’t eat fish or any other seafood. What we can’t say for sure is whether they consumed deer or drank milk, for example.
Normally, at archaeological sites, we find animal remains, which allow us to compare human and animal diets. But in this case, we don’t have those animal bones. However, we can compare findings with other sites from the same region and period that do have such remains. From that, it’s clear that these people ate like typical Neolithic farmers. They primarily consumed land animals—most likely cows, sheep, and pigs.”
Bone remains as found in the burial mound.
What was the difference between the hill tribe and the people in the valley?
"The main difference was in their burial rituals and the shorter breastfeeding period. In terms of mobility, little changed: some moved around, but most stayed in the same place all their lives. Their lifestyle was very similar to that of the valley dwellers, but with subtle cultural differences - like regions in Western Europe that have similar customs but still retain their own identity."
How different were these people from us?
"I am not studying anonymous patterns, but real people. Their bones reveal personal stories: someone who went through sudden physical changes as a teenager, another who was sick for months, or someone who at some point decided to eat more fish. This awareness makes them relatable: they too made choices, adapted and lived their lives - just like us.
One detail I love is the discovery of a dog among the human remains. At first we thought he was 4,000 years old, just like the humans. But dating showed he was ‘only’ 1,000 years old. That means someone in the Middle Ages deliberately buried his dog here, near a prehistoric monument. He probably did not know who lay there, but felt the place was special. So this grave remained a meaningful place for millennia. It was only in modern times, with the advent of large-scale agriculture, that it was lost."
Isotope research: a chemical fingerprint of the past
Isotope research is a clever scientific technique that allows researchers to find out the origin, age and transformation processes of materials and organisms. This is done by looking at isotopes, which are atoms of the same element but differ in the number of neutrons. Some isotopes, such as carbon-12 and carbon-13, are stable, while others, such as carbon-14, are radioactive and decay slowly.
In nature, isotopes occur in a certain ratio. By measuring these ratios with sophisticated equipment, such as a mass spectrometer, scientists can derive valuable information. For example, carbon-14 analysis is used to determine the age of archaeological finds, such as wood, textiles and bones.
By acting as a kind of ‘chemical fingerprint’, isotope analysis helps scientists uncover hidden information from nature and history.
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