Thursday, May 6, 2021

How Stone Age Ancestors Unlocked the Glucose in Plants

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Troy Oakes
Troy was born and raised in Australia and has always wanted to know why and how things work, which led him to his love for science. He is a professional photographer and enjoys taking pictures of Australia's beautiful landscapes. He is also a professional storm chaser where he currently lives in Hervey Bay, Australia.

Early cave paintings of hunting scenes may give the impression our Stone Age ancestors lived mainly on chunks of meat, but plants — and the ability to unlock the glucose inside — were just as key to their survival. Plants rich in starch helped early humans to thrive even at the height of the last Ice Age, researchers say.

While the evidence around meat eating is clear, the role of plant foods is less understood. Animal bones can last millions of years and still show cuts made by human butchering tools, whereas almost all plant remains disintegrate.

But new studies into the remains of plants that do exist are uncovering why and how our ancestors ate them. Dr. Amanda Henry, a paleobiologist and associate professor at Leiden University in the Netherlands, said:

“Plants were the staples. They were the foods that formed the basis of our calories in most environments.”

Tubers and cereals are full of starch — making them good sources of glucose, which is important for brain growth as well as energy, says Dr. Henry. She leads a project called HARVEST, which is studying the diets of early human species and the role of plants as food. Tubers are organs where plants store nutrients — modern examples include potatoes and yams.

Ground stones were a 'major evolutionary success' as they allowed people to unlock the energy in plants by making flour. Image credit - José-Manuel Benito Álvarez/Wikimedia commons, licenced under CC BY-SA 2.5
Ground stones were a ‘major evolutionary success’ as they allowed people to unlock the energy in plants by making flour. (Image: José-Manuel Benito Álvarez/Wikimedia commons, licensed under CC BY-SA 2.5)

Some of the earliest evidence she found of eating tubers and cereals dates back 40,000 years, to the Paleolithic era. Neanderthal remains discovered in caves in Iraq and Belgium show that our cousins likely ate water lily tubers, and grains from relatives of wheat and barley grasses.


But unlocking the energy in them required innovation. The grains may have been eaten green when they are easier to digest, but many tubers are toxic raw, says Dr. Henry, adding:

This not only releases energy, but it also makes tubers safe to eat, Dr. Henry said:

The Neanderthal remains indicate they ate a wide variety of plant foods. This throws doubt on a theory that they died out because they had a narrower diet than our direct ancestors, Dr. Henry says. Other researchers have found earlier evidence of cooked tubers from South Africa in a fireplace dating back more than 100,000 years.

During the last glacial period when ice caps expanded to cover much of northern Europe, there was an explosion of a new technology driven by the need for processing new sources of plant food: the ground stone.

Cave paintings often depict hunting activities but plants were the staple food for Stone Age people, say researchers. Image credit - Gruban/wikimedia commons, licenced under CC BY-SA 2.0
Cave paintings often depict hunting activities, but plants were the staple food for Stone Age people, say researchers. (Image: Gruban / wikimedia commons, licenced under CC BY-SA 2.0)

It was a major evolutionary success, dating back about 30,000 years, says Dr. Emanuela Cristiani, associate professor in prehistoric archaeology at Sapienza University of Rome, Italy. Hunter-gatherers primarily used knapped tools, made from big pieces of stone, says Dr. Cristiani, adding:

Amanda Henry, from Leiden University in the Netherlands, said:

Through a project called HIDDEN FOODS, Dr. Cristiani is studying diets of humans in southeastern Europe from the late Paleolithic era — when they were hunter-gathers — to the Neolithic era, when there is the first evidence of farming in the region about 8,500 years ago. She is also exploring the evolution of plant food processing technologies.


Grinding meant people could make flour, which is another way of unlocking the energy in plants. The team found evidence in ground stones and plant remains in dental calculus that hunter-gatherers in the central Balkans ate a lot of wild oats, legumes, and acorn flour, says Dr. Cristiani.

Researchers have found evidence that hunter-gatherers in the central Balkans ate wild oats, legumes and acorn flour. Image credit - Pxhere, licensed under CC0
Researchers have found evidence that hunter-gatherers in the central Balkans ate wild oats, legumes, and acorn flour. (Image: Pxhere, licensed under CC0)

The earliest evidence of flour dates back 30,000 years and was found in Russia, the Czech Republic, and Italy. It is likely that hunter-gatherers at the team’s Italian research site ate cattail plants, which are abundant in a nearby river. Dr. Cristiani said the flour makes a sweet-tasting bread, adding:


The average Paleolithic person who survived infancy seems to have lived to age 50 or 60. Dr. Henry said:

These early humans are likely to have died primarily from a combination of infections, parasites, and physical trauma, she says. Once people started settling and rearing animals and crops, disease levels rose — mainly because they jumped from animals to humans — and life expectancy appears to have fallen. Dr. Henry said:

Today, some people seeking a healthy alternative to modern industrialized diets look to the eating styles of our hunter-gatherer ancestors for inspiration. The so-called Paleo diet eschews cereals, recommends few carbs, and promotes meat and vegetables. But archaeologists say it does not represent the full diet of hunter-gatherers, who ate cereals and relied on carbohydrates.

Hidden Foods

Researchers found remains of legumes, oats, and acorns in 10,000-year-old teeth from the last hunter-gatherer groups who built villages along the Danube river. Dr. Cristiani said:

Hunter-gatherers were looking for calories, so carbohydrates in tubers and cereals would have been important. Dr. Henry said:

Diversity was integral to people’s diets, as was their ability to move to new regions. Dr. Cristiani added:

Provided by: Alex Whiting,  [Note: Materials may be edited for content and length.]

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