Why archaeologists are arguing about sweet potatoes

www.popsci.com ^ | 04/13/2018 | Staff

[Red Badger]

A Japanese variety of sweet potato

Pixabay _______________________________________________________________________________________________________________

At some point, sweet potatoes crossed the Pacific. This much we know. As for the rest—How? When? Why?—we’re just not sure.

Or, to be more clear, some people are sure they’re sure, and others disagree.

Sweet potatoes have been at the center of a massive archaeological debate for many decades now, and a new paper in Current Biology has only stoked the flames. It uses genetic data from sweet potatoes and their relatives to establish a phylogenetic tree of their evolution, thereby demonstrating that the tubers existed in Polynesia before humans lived there.

But let’s back up for a second. Why do we care so much about sweet potatoes?

The debate about sweet potatoes is, in a way, a debate about human contact (though to be honest, it’s also definitely about the taters themselves). Before Europeans colonized much of the world, native people on both sides of the Pacific traveled fairly long distances across the ocean. South Americans made it all the way out to the Galapagos Islands, which are upwards of 620 miles off the coast of Ecuador. Pacific Islanders, including the predecessors of modern-day Samoans, Tongans, and Maoris, also managed to spread across the myriad dots of land scattered around their patch of the ocean. Those islands, especially the much-larger New Zealand and Australia, are hundreds or thousands of miles apart, which means Pacific natives regularly ventured across the ocean to explore new lands.

All these people clearly shared an affinity for the sea and serious ship-building skills. But they also shared a love of sweet potatoes. They’ve been a core crop for thousands of years, predating Columbian-era exploration. But...how? Sweet potatoes originate in South America, which is thousands of miles away from most of Polynesia.

There are three basic ways this could be possible:

South Americans ventured over to Polynesia, bringing sweet potatoes with them. Native Polynesians then either deliberately cultivated this new crop, or the seeds accidentally got fertilized and sweet potatoes began to grow naturally.

Polynesians traveled to South America, then brought sweet potatoes back with them on their return trip, presumably with the intent to plant the seeds when they got home.

Sweet potatoes, or just their seeds, floated from South America to Polynesia, no human action required.

Again: it’s still not clear which of these is true, but archaeologists have used sweet potatoes as evidence to show that Polynesians and South Americans either definitely did or definitely did not have contact for years now, with varying views on who traveled in which direction.

Apart from historical accounts from native peoples themselves, there’s mostly no evidence either way for South Americans versus Polynesians doing the carrying—there’s just evidence for human transportation versus natural spread. (The accounts themselves suggest that Polynesians may have been the ones to venture out, returning much later with tater in tow.)

One key puzzle piece: what words we use to identify the tuber. Since sweet potatoes definitely originated in South America, researchers looked at the terms for the vegetable in use by native peoples, then examined how those terms compared to the words used in Polynesia and East Asia. In South America, for example, sweet potatoes are called kuala, kumara, cumal, and other words that bear a striking similarity to the terms used in much of the Pacific Islands: umala, kumala, kumara, and so on.

Central Americans called them camote or camotil, which is nearly identical to the terms used in East Asia (kamote, camote). In the Caribbean, sweet potatoes went by Spanish words: batata or aje, which is what they’re called in New Guinea and nearby islands.

These linguistic differences don’t precisely mirror sweet potato introduction, since old names can continue to apply to new varieties (in other words, you might name a delicious new treat after something pretty similar you’re more familiar with), and we know that the tubers were actually brought west multiple times—European explorers definitely brought some over.

Sweet potato spread according to the tripartite hypothesis

Infographic by Sara Chodosh _________________________________________________________________________________________________________________

Regardless of how many introductions there were, these patterns would all necessitate direct contact between native peoples on either side of the Pacific. But not all researchers agree. Just because the words are similar doesn’t mean that the initial introduction occurred between those two people—languages evolve, after all.

The recent paper in Current Biology argues that DNA evidence suggests the Pacific Island sweet potato family branched off from the American one long before humans were sailing. Thus, the seeds or the veggies themselves must have floated their way across the ocean.

This actually isn’t as crazy an idea as it sounds. It’s the primary way that biologists think coconuts spread from island to island—the coconuts float from shore to shore. One 2008 study actually modeled the possible paths from South America to various islands, based on observing ocean currents, to see whether it was even feasible. The answer: a resounding “yep!” Over the hundreds upon hundreds of years that sweet potatoes could have traversed the ocean, seeds certainly might have floated along with currents and found new homes on other islands. It’s still uncertain whether sweet potato seeds remain viable after the minimum 120 days that the researchers estimated the journey would take, but the theory remains feasible.

Some batátas

Pixabay ___________________________________________________________________________________________________________________

This new paper shows that DNA from sweet potatoes and related crops suggest that early specimens collected from Polynesia must have diverged from other tubers more than 100,000 years ago, long before humans would have been sailing across the ocean. Even the earliest estimates of people-based transportation put it circa 1000 CE, or possibly a few hundred years before that.

Previous genetic evidence had actually argued the opposite. A PNAS paper from 2013 used DNA from chloroplasts (the little organelles plants use to convert sunlight to energy) to show that sweet potato lineages have actually been recombining across islands and oceans for a long time with human help. The more recent paper argues that chloroplast DNA isn’t necessarily an accurate way to estimate phylogeny, since chloroplast genomes can mix between species in ways nuclear DNA can’t.

Whatever the reality, the archaeological debate on human contact across the Pacific will likely rage on, with sweet potatoes remaining at its heart—and in all of our hearts, really. Long live the sweet potato and all its varieties. Long live the tuber.

[dfwgator]

“It’s not a question of where he grips it! It’s a simple question of weight ratios!”

[Rebelbase]

I’d hate to be a bird and pass a sweet potato. Ouch!

[Lazamataz]

In the south, we fry ‘em,

Secrets, please. I have -- to date -- been unsuccessful.

[Rebelbase]

Sweet potato article about a former NFL player who quit to become a farmer and grow sweet potatoes, donating a portion of the first harvest to food banks. He learned to farm watching youtube videos.

Former NFL star dumped 20 tons of sweet potatoes on a Chapel Hill lawn – with good intent

http://www.newsobserver.com/news/local/article199489679.html

[V K Lee]

Fried:
This is from Blue Mesa Grill, served as a restaurant would serve tortilla chips - and just as delicious.
https://bluemesagrill.com/2016/04/06/sweet-potato-chips/

Have sliced them a bit thicker, 1/4” and fried till dark and crisp on the outside, soft in the center. Sprinkle cinnamon/granulated sugar mixture and dig in.

Baked:
https://www.realsimple.com/food-recipes/browse-all-recipes/baked-sweet-potatoes
NOTE: when cooking the sugar oozes from the pierced skins (best to line pan with aluminum foil)
Prefer to bake and serve with butter only, leaving the cinnamon/sugar, maple syrup to the other guests.

Sweet Potato Souffle:
BTW - contrary to popular belief, few really appreciate marshmallows on top of sweet potatoes.
https://www.southernliving.com/dish/casserole/kathy-g-sweet-potato-casserole-praline-topping-video

Sweet Potato Pie:
Tastes much like Pumpkin Pie
https://www.tasteofhome.com/recipes/sweet-potato-pie

Unlike Whites,Idaho or Russet, it is not recommended you eat sweet potato skins. For mashed sweet potatoes, bake in oven and skin, mash them with butter and seasonings (your preference)and a bit of cream. No gravy needed, have yet to find one that enhances the flavor.

Sweet Potato varieties
http://www.all-about-sweet-potatoes.com/sweet-potato-varieties.html

23 Different Recipes for Sweet Potatoes
http://www.geniuskitchen.com/ideas/best-sweet-potato-recipes-6225?c=15886

PS You can also use the baked, mashed sweet potato in waffles or pancake batter:
https://www.foodnetwork.com/recipes/alton-brown/sweet-potato-waffles-recipe-2013843

Here’s to Good Eats.

[blam]

"There is every reason to believe, but no definitive proof, that the megalithic structures underwater off Japan were made by the Jomon, who predate the melting of the glaciers of the Ice Age."

I'm a big fan of the Jomon but, I don't believe those structures are man made. There are many just like them nearby on land....and, they're natural.

[PIF]

Could be, then again there is only conjecture (belief/theory) one way or another, like the leveled mountain top in Romania with an outcropping that looks like a carved Neanderthal head ... was it carved or is it just erosion?

[blam]

"A yam is an African sweet potato, there are some differences between what we typically call yams and what we call sweet potatoes."

The slaves from Africa, upon encountering the sweet potato, called it a yam because it resembled yams from their country.

[blam]

African Tuber Of Yam

[RegulatorCountry]

I’d understoood that they actually were African yams that got here the same way okra did, they brought seed pouches. A sweet potato plant and a yam plant don’t look the same and neither do the root tubers. Maybe in grocery chains in other parts of the country they’re interchangable, but I’m accustomed to distinctions being made. Candied yams are served as a vegetable. Sweet potatoes are not unless baked or made like French fries, a fairly recent thing.

[blam]

Yam (Vegetable)

On Amazon, I saw 5 yam plants on sale for $40.00 plus $3.40 shipping.(15 left)

[Cold Heart]

A 2012 Brazilian study of GPT (Gut Passage Time) in various birds and seeds had the longest GPT at 60 minutes. Shortest was 6 minutes.

[D Rider]

Birds also carry seeds in their feathers. Some seeds are designed to do this. I have no idea what a sweet potato seed looks like.

[D Rider]

Birds also carry seeds in their feathers. Some seeds are designed to do this. I have no idea what a sweet potato seed looks like.

[D Rider]

They are interchangeable when cooking. Did that 40 years ago.cut the yams and sweet potatoes into disks, place them into a Pyrex baking dish in a checkerboard fashion. Cover them with brown sugar and orange juice and bake until done. Very beautiful and delicious.

[colorado tanker]

My grocery store can’t figure out if they are sweet potatoes or yams. The last few months they’s been sweet potatoes. Regardless, we’re having baked sweet potatoes with our pork chops tonight. Yum!

[gleeaikin]

“early specimens collected from Polynesia must have diverged from other tubers more than 100,000 years ago”

We have no way of knowing if people might have developed ocean transport before any struggling civilization might have been disrupted/destroyed by our most recent Ice Age.

[SunkenCiv]

The Polynesian *word* for sweet potato isn't a polynesian one, its a loanword from Precolumbian America. The sweet potato can't float its way on salt water (assuming it will float at all, for any length of time) without dying. Either the Polynesians encountered the people from Precolumbian America *in* Precolumbian America, or the Precolumbian Americas were already on at least some of the islands -- precisely what the Easter Islanders told Thor Heyerdahl.

[Red Badger]

Ice Ages make it easier for people to travel. It’s a lot easier to walk across ice than water!...............