And that’s not all, according to a more recent study (last week, actually), sweet potatoes may tell us about early human exploration.

The sweet potato originates in South America, but the plant predates European explorers in Oceania. To many historians, this has always been a mystery. When did it get there? How? Natural seed dispersal? Humans?

A study in the 1970s by a Hawaiian researcher hypothesized that the sweet potato was first dispersed by Polynesian voyagers between 1000 and 1100, then by Spanish explorers heading from Mexico to the Philippines in 1500, and finally, by Portuguese traders traveling from Central America to Indonesia around the same time.

Called the tripartite hypothesis, the theory relied on archeological and linguistic evidence (the sweet potato is called kuumala in Polynesian languages, and kumara, cumar or cumal in Quechua speakers in South America). Now, French scientists are throwing genetic evidence into the mix.

The researchers analyzed 1,245 sweet potato samples from Central and South America as well as Oceania and a few from Southeast Asia and Madagascar. While most were modern plants, around 50 were historical herbarium specimens. And while the modern samples provide little evidence of early plant movement, the historical samples provide strong genetic support of the hypothesis, especially the first movement by Polynesian voyagers.

This stunning result implies that these voyagers may have traveled 5,000 miles or more across the open ocean!

The research was published last week in the Proceedings of the National Academy of Sciences. More information on the Polynesian travelers can be found here.

Image: Llez/Wikipedia

Take wild spotted horses depicted by our ancestors as having a white coat with black spots in cave paintings around 25,000 years ago. Scientists had evidence of bay and black horses, including a 2009 published DNA study of ancient horses dating back as far as 12,000 years ago, but no proof of the dappled horses.

A team of international researchers decided to try older samples—31 pre-domestic horses dating back as far as 35,000 years ago from Siberia, Eastern and Western Europe and the Iberian Peninsula, analyzing bones and teeth specimens from 15 locations.

They found that six of the samples shared a genetic variant called LP that is associated with leopard spotting, providing the first evidence that spotted horses existed at this time. In addition, 18 horses had a bay coat color and seven were black, meaning that all color phenotypes distinguishable in cave paintings—bay, black and spotted—existed in pre-domestic horse populations.

The study was published earlier this week in the Proceedings of the National Academy of Sciences.

“Our results suggest that, at least for wild horses, Paleolithic cave paintings, including the remarkable depictions of spotted horses, were closely rooted in the real-life appearance of animals,” says study co-author Michael Hofreiter.

Archeologist Terry O’Connor concurs. “Our research removes the need for any symbolic explanation of the horses. People drew what they saw, and that gives us greater confidence in understanding Paleolithic depictions of other species as naturalistic illustrations.”

Want to learn more? ScienceNOW offers a reason why the LP gene was absent from more recent samples (as studied in the 2009 paper):

As for why the spotted phenotype became more rare after 14,000 years ago, the team points out that some modern horse breeds with two copies of the LP gene suffer from night blindness, which would have made prehistoric horses more vulnerable to predators. The researchers speculate that the gene might have been beneficial during the ice age, when a white spotted coat could serve as camouflage in snowy conditions, but later became rare and disadvantageous until rediscovered by modern horse breeders.

Image: Pruvost et al./PNAS

During the last century, the story about the peopling of the Americas seemed relatively straightforward. But over the past few decades, new evidence has challenged all we thought we knew about the route, timing, and origins of these first Americans. Now an archaeological discovery in central Texas has turned everything on its head once again.

Nearly 80 years ago, North American archaeologists identified what they believed to be the earliest stone tools in the New World. Characteristic of the Clovis culture, stone tools with “fluted” spear points first appeared about 13,000 years ago and were found throughout North America.  However, early versions of these stone tools have never been found outside North America, in places like northeast Asia or Alaska, where the first Americans started their journey into the New World. This lack of continuity of Clovis culture tools outside North America has led some to question whether this culture really did accompany the First Americans.

In this week’s issue of Science, a team of North American archaeologists report the first concrete evidence debunking the so-called “Clovis First” archaeological model of the peopling of the Americas.

The team of archaeologists, led by Michael Waters of Texas A&M University’s Center for the Study of the First Americans, has been excavating at the Debra L. Friedkin archaeological site northwest of Austin for five years. This site contains stone tools and other artifacts that span American prehistory, including thousands of Clovis points.

But whereas the appearance of Clovis points in most archeological dig sites marks the earliest evidence of human occupation, artifacts discovered at this site predated the Clovis points.

As Waters recalls, “The kicker was the discovery of nearly 16,000 artifacts below the Clovis horizon that dated to 15,500 years ago.” That’s 2,500 years older than any Clovis points unearthed in the Americas.

Among the 16,000 artifacts excavated are various types of small blades, choppers, and scrapers made of chert. Their small size has led some to theorize that these tools represent a ‘mobile toolkit’ that could easily be packed up and moved. Now identified as the Buttermilk Creek Complex, this assemblage represents the oldest archaeological site in North America.

The early age of this site coincides with recent genetic and paleoenvironmental evidence that people first crossed into the Americas much earlier, perhaps as early as 30,000 years ago, and spread into North America by about 17,000 years ago. But the archaeological record in support of an early arrival has, until now, been limited.

Many experts believed more archaeological evidence was needed to support the model of an early arrival. The Buttermilk Creek Complex provides that evidence. The discovery of a huge assemblage of stone tools that predate Clovis culture also puts to rest the conventional wisdom that the first Americans brought the Clovis culture with them from Asia.

As Waters explains, “It is now time to abandon once and for all the ‘Clovis First’ model and develop a new model for the peopling of the Americas.”

Anne Holden, a docent at the California Academy of Sciences, is a PhD trained genetic anthropologist and science writer living in San Francisco.

Image courtesy of Michael R. Waters

California’s Channel Islands, a group of eight islands just off the coast of southern California, house one of the richest and most diverse collections of land and marine animals anywhere in the world. But a new discovery into the island’s ancient past reveals a rich history of human settlement as well.

In a new study published last week in the journal Science, a team of archaeologists, led by the University of Oregon and the Smithsonian Institution, has unearthed a massive collection of stone tools that date back to the islands’ earliest American Indian settlers.

Excavations at three sites on Santa Rosa and San Miguel islands yielded scores of projectile points and oddly shaped tools called “crescents.”  In many cases, these tools were so delicate that there’s only one place they could have been used: underwater.

“This is among the earliest evidence of seafaring and maritime adaptations in the Americas,” said Jon Erlandson, executive director of the Museum of Natural and Cultural History at the University of Oregon and one of the paper’s co-authors. “The points we’re finding are extraordinary, the workmanship amazing. It’s a very sophisticated chipped-stone technology.”

These tools date to between 12,200 and 11,400 years ago, several thousand years after the first Americans are believed to have crossed the Bering Strait from Asia in present-day Alaska. When the first people arrived at the Channel Islands, they weren’t islands at all, but one large island surrounded by shallow sea. Sea levels in this region were about 200 feet lower than they are today, and the islands were connected to each other.

What makes these archaeological finds so exciting to researchers is not only their abundance and preservation, but their style. The delicate stemmed and crescent tools are entirely unlike the more well known Clovis point technology found throughout much of North America. The Channel Islands’ discovery lends credence to an increasingly popular idea: the makers of the maritime tools took a more coastal path from Alaska than their Clovis-making counterparts.

Several years ago, Erlandson proposed the idea of a “kelp highway,” from Japan to California, rich in marine life such as seals, seabirds, and fish. Could the Channel Islands settlers be the descendants of these early travelers?

While many questions remain, this and previous discoveries on the Channel Islands have given archaeologists a considerably better understanding about the earliest settlers of coastal California. “[This discovery] shows that very early on, New World coastal peoples were hunting such animals and birds with sophisticated technologies that appear to have been refined for life in coastal and aquatic habitats,” said Torben C. Rick, curator of North American Archaeology at the Smithsonian and one of the paper’s co-authors.

But uncovering how and when these settlers arrived will require more digging. Erlandson and Rick hope to head back to the island in search of earlier sites, retracing these coastal peoples’ steps up the coast of California.

Anne Holden, a docent at the California Academy of Sciences, is a PhD trained genetic anthropologist and science writer living in San Francisco.

Image courtesy of Jon Erlandson