Top Human Origins Stories of 2003

Friday, January 02, 2004

Our Genes May Prove It: We Are Family

Humans are all so closely related that our entire population shows less genetic diversity than that of a small group of chimpanzees. It’s almost as though we all came from the same town—and perhaps we did. This year geneticists announced that each of us is descended from a population made up of as few as 2,000 hunter-gatherers who lived in northern Africa between 70,000 and 140,000 years ago. If the analysis holds up, it supports the controversial out-of-Africa theory that Homo sapiens evolved in Africa before migrating to other continents.

This scenario is based on a study by Marcus Feldman, a population geneticist at Stanford University; Noah Rosenberg, a computational biologist at the University of Southern California in Los Angeles; and Lev Zhivotovsky, a geneticist at the Russian Academy of Sciences in Moscow. They examined short, repetitive fragments of DNA called microsatellites, markers found in every person. “We used 377 markers that are generally located in noncoding regions of the genome, ones that are likely to be neutral, where there is no natural selection involved,” says Rosenberg. The beauty of microsatellites is that they mutate frequently and at a steady pace, enabling scientists to infer from them when human populations first diverged from each other. Studying those mutations in 1,056 individuals clustered in 52 population groups around the world allowed researchers to plot successive waves of migration to Europe, Asia, and the Americas after those first hunter-gatherers left Africa. “We’re now trying to confirm these results using different models of how evolution took place,” says Rosenberg.           

Michael W. Robbins

This Very Old American House Sheltered Prehistoric Nomads

The place doesn’t look like much, just a circular pile of slab-shaped rocks weighing about 50 pounds each. There are also subtle signs of fire damage: bits of mud used as mortar have a burnished red hue, like clay baked in an oven. All things considered, however, the recently unearthed site is remarkably well preserved. Dozens of stone knives, scrapers, and spear points found there suggest it may have been a weapons-making depot for Folsom hunters, prehistoric nomads who roamed North America more than 10,000 years ago.

The most extraordinary thing about the crude shelter is its location, on top of Tenderfoot Mountain, an 8,600-foot mesa in the southern Rockies near Gunnison, Colorado. Folsom hunters ambushed and speared bison and elk on the Great Plains, from what is now Nevada to Iowa, and researchers had surmised that they must have lived in ephemeral hide shelters that left no traces. “It could be that we’ve had blinders on and that the Folsom people were more mountain oriented than we thought,” says Mark Stiger, an anthropologist at Western State College in Gunnison. “Perhaps they just hunted on the plains but lived up here the rest of the time.”

Stiger began digging on Tenderfoot after he happened upon some bits of Folsom spear points while surveying the proposed site of a communications tower. He has since identified 15 other Folsom-era sites on the mountain that have yet to be unearthed. “There wasn’t any surface evidence of the house on the area we excavated,” Stiger says. “The other areas may have houses, or they may be something different. We’ll see.”

Michael W. Robbins

Land Bridge Theory Tested

The most plausible explanation of how humans first settled the Americas—Ice Age hunters pursuing game walked from Siberia to Alaska over a land bridge—has gained wide acceptance in recent years, although scientific evidence has been thin at best. In 2003, it got thinner.

The yardstick for determining when the hunters crossed over is farther south, in Clovis, New Mexico. There the oldest archaeological site in North America with reliably dated tools and artifacts shows a human presence as early as 11,500 years ago. For the land bridge concept to hold, sites much older than Clovis would have to be found along the route. Only one has been found—at Ushki Lake, along the Kamchatka River, in Siberia. It was discovered in 1964 by archaeologist Nikolai Dikov, who found spear points and tools that he carbon-dated to about 14,300 years old. That would have given tribes sufficient time—3,200 years—to trek over the land bridge and down to Clovis.

Two years ago, American archaeologists reexamined the site. They brought back charcoal found with primitive tools in an ancient fire pit. In July they published a surprise: Based on radiocarbon dating, the charcoal is only about 11,000 years old, contemporary with Clovis. “This probably eliminates the people of Ushki Lake as the progenitors of Clovis,” says Michael Waters, an anthropologist at Texas A&M University in College Station who participated in the study.

The strength of the land bridge story was further undermined by an analysis of skeletal remains found in Baja California that was published in September. Rolando González-José, an anthropologist at the University of Barcelona, and his team had minutely measured 33 skulls that were between 300 and 2,700 years old, only to discover that they resembled neither prehistoric northeastern Asians—those who presumably would have crossed the land bridge—nor modern American Indians; the fossils looked more like the progenitors of Southeast Asian peoples.

Some anthropologists, including González-José, say the Baja skulls suggest that Southeast Asians traveled to the Americas by boat before the Clovis era. But others disagree. Tom Dillehay, an anthropologist at the University of Kentucky, says morphological anomalies don’t necessarily prove there were earlier migrations: “They may indicate some genetic drift, or they could link to some parallel adaptations, or perhaps they resulted from interbreeding with other local populations.”

Despite the Ushki and Baja challenges, the land bridge theory is not dead. Waters, for one, still has faith in the hypothesis because there is so much territory left to excavate. “Siberia is a big place,” he says, “and very few archaeologists are working there.”

Michael W. Robbins and Jeffrey Winters

Ötzi’s Boots Were Made for Walking

So you spend five millennia shopping for comfortable shoes, and you still can’t find a pair that fit. Then this chap from the Czech Republic hikes up a mountain in a pair of bark-net, straw-stuffed, bearskin-soled boots modeled on the footwear of a 5,300-year-old frozen mummy—and he doesn’t develop a single blister. In fact, he makes the extraordinary claim that the makeshift shoes are better insulated and better cushioned than modern-day hiking boots and provide superior traction. Petr Hlavácek, a professor of shoe technology at Tomas Bata University in the Czech city of Zlín, created five pairs of shoes replicating those worn by the celebrated Stone Age ice man Ötzi on his prehistoric trek in the Ötztal Alps in northern Italy. Then he and three bold friends put the shoes on—sans socks—and retraced the ice man’s final footsteps to the glacier where his body was found in 1991, a distance of some 12 miles. Even when they stepped into icy streams, they felt no discomfort. “The shoes were full of water, but after three seconds it was a very comfortable, warm feeling,” says Hlavácek, who displayed the shoes in Offenbach, Germany, in July. “This is because the layer of hay is full of airholes, and air is the best warm insulator.” Furthermore, the linden-bark-net uppers were loose enough to even out the overall pressure of the boots, so that blisters did not form. And the bearskin soles of Ötzi’s shoes—tanned with bear brains and liver—provided an excellent grip upon the rocky mountain paths.

Ötzi may have been well shod, but that apparently did not enable him to outrun his enemies. The latest findings, announced in August, show that he stood his ground and may have fought off several foes before dying of an arrow shot to his left shoulder. Molecular archaeologist Tom Loy of the University of Queensland in Brisbane, Australia, analyzed blood from Ötzi’s arrows, knife, and coat and found DNA from four separate people—not including the ice man himself. Although their identities can never be known, the absence of an arrow shaft in his shoulder—only the arrowhead remains—suggests that one was a companion who pulled out the shaft. As for the others, they were probably rival hunters. According to Loy, Ötzi’s long, lightweight arrows indicate that he was a specialist hunter of ibex, long-horned goats that live high above the tree line; such arrows would not have worked well in the forest, where they would readily have become tangled in the branches of trees. Loy speculates that the ice man’s trade may have taken him into mountain passes whose boundaries were disputed: “He could easily have run across someone from another valley who took umbrage at finding Ötzi hunting in territory he considered his own.”

Josie Glausiusz

Next Page
1 of 2
Comment on this article
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

ADVERTISEMENT
ADVERTISEMENT
Collapse bottom bar
DSCDecCover
+

Log in to your account

X
Email address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it emailed to you.

Not registered yet?

Register now for FREE. It takes only a few seconds to complete. Register now »