Starch found on 4,400-year-old teeth is evidence of oldest use of spices, plants by humans.
What is curry?
Curry is more than just a single spice or flavor.
There are a wide range of curry dishes made all over the world, including India and much of Asia, Africa, the Caribbean and Central Europe.
The main thing all of them have in common is that they’re made from a combination of many different spices. Several dishes include ginger, turmeric and cumin, and almost all of them have some sort of hot element, such as chilies.
The dishes can be hot, mild, sweet or savory and can be red, green and other colors beyond the classic yellow. They can be vegetarian or include beef, fish and other meats.
Curry powders found in grocery stores today represent only a small combination of spices. Those powders probably originated in the 18th Century and were sold by Indian merchants to British government officials and others stationed in the country.
Eggplant curry recipe from current villagers of Farmana, India
3 tablespoons oil
1 onion, medium coarsely chopped
Small piece ginger, coarsely chopped
2 tsp red chili powder
2 tsp turmeric
Sugar and salt to taste
1 tomato, large, chopped
Coriander, fresh leaves
Wash, pat dry and prick eggplant. Roast eggplant over open flame or in a tandoor/preheated oven until the skin scorches and starts peeling off and eggplant start to shrink. Cool by dipping in water. Remove skin and mash the pulp completely.
Heat oil in a kadai/pan. Add onion and sauté for a few minutes. Add the turmeric and red chilli powder and cook for a minute. Add sugar and then ginger and cook for another minute. Add mashed, roasted eggplant. Cook for seven to eight minutes over medium heat, stirring continuously.
Add salt to taste. Add tomatoes and cook on medium heat for seven to eight minutes or until oil separates. Garnish with chopped coriander leaves and serve hot.
The love of eggplant goes way back for Arunima Kashyap. It was the only food she'd eat when she was little, and it's still her favorite, she said.
For a long time, that love was a one-way street. The eggplant gave, and Kashyap ate.
But then the scientist, who grew up in India, found a way to give back to the humble eggplant, and to some of the other plants and curry spices she adores.
Working with Steven Weber, an archeologist and associate professor at Washington State University Vancouver, Kashyap was able to track down some of the plants' ancient lineage and uses.
From what she's uncovered, it appears that eggplant, mango and some elements of curry spices were used in recipes 4,400 years ago in the Harappan civilization, which flourished in a region that covered part of modern day Pakistan and Northwest India.
It's the oldest evidence of use of the spices and plants yet recovered.
And it also appears that cows were also enjoying the culinary complexity back then, she said.
"Much like the people there do today, back then it appears they fed leftovers to cattle, or that cattle were eating leftover human food from garbage piles," Kashyap said.
Kashyap made the discoveries through analyzing starches preserved on teeth — from both human and cows — and on pot shards from a dig site in Farmana, India.
Plants store energy in starch grains as part of photosynthesis. And unlike seeds or larger plant parts that decay more rapidly, the microscopic starches are more easily preserved in tooth enamel and on the coatings on tools, and they can remain there for thousands of years.
In her study, Kashyap found preserved grains of eggplant, turmeric, ginger and other foods on items unearthed in Farmana.
That the plants were found on teeth is especially interesting, because it proves that people 4,400 years ago were cooking and consuming the spices — which are a very basic part of many types of curry, Weber said.
"We don't know that they were putting all of them together in a dish, but we know they were eating them at least individually," he said.
There's a lot more to curry than just turmeric and ginger. And there is no one definitive type of curry — the dishes vary from region to region, both in India and all over the world, Kashyap said.
"Being Indian I'd say ginger and turmeric, they're certainly part of curry, but not all of it," Kashyap said. "With that, you don't get the (hot) spicyness."
Tumeric and ginger give many curries the classic yellow-gold appearance. There are some native types of both plants that grow in the area in Northern India.
The word curry itself goes back to English traders sometime between the late 1300s and mid 1600s, and it is likely derived from the word kari, which means either pepper or spice in a South Indian dialect.
It's likely that Indian people ate curry dishes way before then, but because foods easily decay over time, it's been hard for scientists to prove it.
The evidence that they were eating some components of the dish 4,400 years ago is by far the oldest every found, Kashyap and Weber said.
Each plant — turmeric, ginger, mango, apples, blueberries, potatoes — has highly individualized starch granules.
The preserved grains, whether in India or the United States' Pacific Northwest, can indicate where and how specific plants were used in the past.
The Smithsonian Institution has a growing starch grain database, but it's far from complete. There are still thousands upon thousands of plants left to catalog.
Kashyap has already made a sizeable contribution to that database. So far, she's identified 120 starch grain types that have been added to it, she said.
"It takes a tremendous amount of time to do this — one plant takes me about three days," Kashyap said. "You have to study hundreds of grains for each plant."
But it's worth it, she said, because one of the starch grains she was able to catalog, along with ginger and turmeric, was for her beloved eggplant.
"Eggplant is my favorite starch," she said, laughing. "Part of the reason for that is I really love eggplant, so it was great that I was able to find (and detail characteristics of) its starch."
Eggplant starch grains are somewhat oval, with a shallow area and "a very beautiful cross under polarized light," she said.
"They're very cute," Kashyap said, with an amused smile. "You have to find some love in them to study them."
Starch grains change shape during the cooking process. Another part of Kashyap's research was to investigate how those foods were cooked in the ancient past.
So she asked current residents of the area for their curry and chutney recipes, then cooked them herself and studied the starches over time to see how they changed.
"I'd make the dishes, but it was like you stop at 1 minute, 2 minutes, 10 minutes and collect samples each time to see how the starches change," Kashyap said. "And then we cooked them all different ways, so you can tell the difference (in starch shape) between roasted eggplant, boiled eggplant, fried eggplant."
From that work, it looks like villagers in ancient Farmana were possibly cooking curried dishes in terra cotta, or unbaked, earthen pots, then eating them and sharing them with village cattle — something that still happens in rural villages to this day.
"In our experiments, we did a lot of pot cooking on the surface of unglazed pots," she said. "We shattered a lot of them in the process. But as you build up information, you can tell how people cooked in the distant past."
Studying the spices is also interesting because it can show the pathways of ancient trading networks, Weber said.
That, in turn, can indicate how various food crops ended up distributed around the world.
"It helps you understand the prehistory," Weber said. "You can look at how things got the way they are, how things moved across the landscape."
Studying the ancient use and distribution of plants and seeds is fascinating, but it's also important to note that the findings don't just pertain to ancient cultures — they're also highly relevant today, Weber said.
Weber, who is focused on the archeological study of plants, runs the archaeobotany lab at WSUV. Starch grains are a small part of that work, which also includes looking at seeds, plants and crops that were used in agriculture in past societies in India and around the world.
"Many of these (ancient crop) species were more adaptable to climate change than the crops we have today," Weber said. "When climates change, maybe there are ancient grains that can be incorporated (into farming) in a better way."
Some plants and grains may have gone out of use because they were difficult to mill or harvest. But if those plants are nutritious and hardier than modern food crops, they could be brought back and harvested using modern technological methods, he said.
"There's a lot of knowledge out there, and we can use it," Weber said.
That's something that's already happening in parts of India, Kashyap said.
"In Southern India now, where the climate fluctuates a lot, the people are going back to millets," Kashyap said. "They're more hardy, and they went out of use because they were hard to de-husk. So now they're trying to de-husk them more efficiently."
In Thailand, farmers have started growing rice with patches of millet, to make sure they have something to harvest and eat if the rice crop doesn't grow well, Weber said.
Understanding and preserving ancient plants could be critical to human survival, especially considering that some crops — such as corn — tend to be very genetically uniform, which makes them susceptible to diseases and infestations that could wipe them out.
"One of the things we see in agriculture is a decline in species diversity," Weber said. "That can have consequences down the road."
'Always more work'
Kashyap, who has a Ph.D. from Michigan State University and has done work with the Smithsonian Institute, came to the Pacific Northwest because her husband got a job at Intel in Hillsboro, Ore.
She decided to work with Weber at WSUV as a way to continue to build on her research.
More recently, she also got a job at Intel as a "human factors engineer," which is a bit like an anthropologist that studies human use of technology.
It's fascinating work that she loves, but she also sometimes finds herself drawn to continue her starch studies.
"I'm getting calls for research from people in Asia," Kashyap said. "People are interested in this, and there's always more work to do."