Oldest hand axes found

African discoveries offer glimpse of early tool-making complexityWeb edition : Thursday, September 1st, 2011 OLD AND EDGYA stone hand ax (shown from different angles), dating to 1.76 million years ago, comes from the earliest known culture to have made such implements.P.-J. Texier, copyright MPK/WTAP

A patch of soil in East Africa has yielded the oldest known stone hand axes and picks, examples of what researchers call the Acheulian industry.

Acheulian implements unearthed at Kenya’s Kokiselei site date to 1.76 million years ago, slightly older than previous finds (SN: 1/31/09, p. 11), say geologist Christopher Lepre of Rutgers University and his colleagues. Carefully shaped, double-edged hand axes and picks lay among much simpler tools — sharp flakes pounded off stones — at Kokiselei, the scientists report in the Sept. 1 Nature.

These finds underscore suspicions that stone flakes used as chopping devices, early tools known as the Oldowan industry, did not get supplanted by hand-ax making, Lepre says. Instead, the more complex Acheulian devices emerged while Oldowan implements — which first appeared about 2.6 million years ago in the same region — were still popular, although it’s unclear how long the two types of tools were used simultaneously at Kokiselei. Hand axes and other double-edged tools typify the Acheulian industry.

Homo erectus, a possible direct ancestor of modern humans, made Acheulian tools and perhaps Oldowan ones as well at Kokiselei, Lepre’s team suggests. Or, another hominid species might have crafted Oldowan artifacts there.

“If Acheulian tools gave hominids an edge in Africa, then perhaps groups lacking that technology were forced to find resources elsewhere, like Eurasia,” Lepre says.

In line with that proposal, other researchers have unearthed H. erectus fossils at Dmanisi, a West Asian site as old as Kokiselei, along with simple chopping stones but no hand axes. It remains unsettled whether H. erectus, which first appeared around 2 million years ago, evolved in Africa or Asia.

Lepre’s team estimated the age of the Kokiselei tools by taking measurements in and around artifact-bearing soil of ancient reversals in Earth’s magnetic field, combined with previously dated volcanic ash layers sandwiching the finds.

Archaeologists familiar with the new paper say that it moves the origin of Acheulian tools back a bit closer to the evolutionary debut of H. erectus, an interesting but not unexpected development.

Excavations at Israel’s 'Ubeidiya Formation have recovered 1.5 million-year-old hand axes and picks, presumably made by H. erectus, that resemble those from Kokiselei, remarks Naama Goren-Inbar of the Hebrew University of Jerusalem. Acheulian sites in Tanzania and India also date to as early as 1.5 million years ago.

Some sets of Oldowan and Acheulian artifacts look much alike, implying that the same hominid species could have produced both tool types, Goren-Inbar says.

Harvard University’s Ofer Bar-Yosef agrees. “Homo erectus could have made all of the stone tools at Kokiselei,” he asserts.

Fossils are needed to confirm that H. erectus made these implements, comments John Shea of Stony Brook University in New York. Simple flakes struck off stones augmented more complex tools throughout the Stone Age, although archaeologists often ignore Oldowan artifacts at modern human sites, Shea argues.

Found in: Anthropology, Archaeology and Humans

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Lager's mystery ingredient found

Galls — growths resulting from a fungal infection — grow on southern beech trees in Northern Patagonia. Scientists recently found a wild yeast that gave rise to a hybrid yeast used to brew lagers in such galls on trees growing in and near two national parks in Argentina.Diego Libkind

Lager beers got their start in Bavaria, but it was a little South American spice that really kicked things off.

Scientists have known for decades that a hybrid species of yeast, Saccharomyces pastorianus, is the microbe that ferments lagers. It’s also well known that one parent of S. pastorianus is the common baking and brewing yeast Saccharomyces cerevisiae. But the other parent of lager yeast has eluded scientists, who have scoured Europe and North America looking for it.

Turns out they were looking in the wrong hemisphere. An international team of researchers led by Chris Todd Hittinger of the University of Wisconsin–Madison and Diego Libkind of the Argentinean National Council for Scientific and Technical Research in Bariloche has tracked the missing wild parent of lager yeast to the beech forests of Patagonia. The researchers report the capture of the newly discovered yeast, dubbed Saccharomyces eubayanus, online the week of August 22 in the Proceedings of the National Academy of Sciences.

“I got chills reading [about] it, I was so excited,” says Barbara Dunn, a comparative geneticist at Stanford University who has been on the trail of the wild yeast herself. “It is incredibly surprising that it is from Patagonia.”

Libkind found S. eubayanus in galls — pale peach, balloonlike structures resulting from fungal infections — on Patagonian beech trees. The galls, full of sugar, house S. eubayanus and another wild yeast that ferment the sugars. It’s generally chilly in Patagonia, just the way lager yeast like it. Lagers are brewed at 4° to 9° Celsius (39° to 48° Fahrenheit).

The S. cerevisiae yeast used for making ales, wines and other alcoholic beverages don’t like the cold, preferring temperatures of about 15° to 25° C (59° to 77° F). So when Germans started brewing beers in the winter to avoid summertime contaminants such as molds, bacteria and other things that skunk beer, the new brewing conditions would have favored the creation of a hybrid lager yeast based on S. cerevisiae and a cold-loving relative, says Antonis Rokas, an evolutionary biologist at Vanderbilt University.

The surprise is where that partner came from. Bavarian brewers started making cold-brewed beers in the 15th century, before Columbus crossed the Atlantic (although the lagers didn’t have a big breakout in popularity until much later). S. eubayanus probably hopped a ship for Europe sometime early in the 16th century. The researchers aren’t sure exactly how S. eubayanus got to Bavaria; perhaps by hitching a ride on pieces of beech wood or barrels made of beech, or on fruit or even in the belly of a fruit fly. However it got to Europe, when S. eubayanus arrived it found a ready-made niche and a partner to merge with, Rokas speculates.

It’s also possible that S. eubayanus lives or lived in some forgotten pocket of the Old World, Hittinger says. “Obviously we haven’t searched every habitat on the entire globe.”

Knowing the identity of the wild parent may help scientists learn how the lager hybrids formed and how domestication genetically changed the yeast, Rokas says. Brewers may also be able to create new hybrid strains that can be tailored for modern brewing practices.

Found in: Genes & Cells

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