Michael Balter

Was North Africa the Launch Pad for Modern Human Migrations

Until very recently, most researchers studying the origins of Homo sapiens focused on the fossils of East Africa and the sophisticated tools and ornaments of famed South African sites such as Blombos Cave. Few scientists thought that much of evolutionary significance had gone on in North Africa, or that the region9s big-toothed, somewhat archaic-looking hominins might be closely related to the ancestors of many living people. Now, thanks to new excavations and more accurate dating, North Africa boasts unequivocal signs of modern human behavior as early as anywhere else in the world, including South Africa. Climate reconstructions and fossil studies now suggest that the region was more hospitable during key periods than once thought. The data suggest that the Sahara Desert was a land of lakes and rivers about 130,000 years ago, when moderns first left Africa for sites in what is today Israel. And new studies of hominin fossils suggest some strong resemblances—and possible evolutionary connections—between North African specimens and fossils representing migrations out of Africa between 130,000 and 40,000 years ago.

Taking Stock of the Human Microbiome and Disease

Programs that helped jump-start the microbiome field have yet to come up with the best way to follow up on their discoveries. Our bodies, inside and out, are teeming with trillions of microbes. Most of them are our friends, helping us to digest food, strengthen our immune systems, and keep dangerous enemy pathogens from invading our tissues and organs. Evidence is building that this resident community of microbes, called the microbiome, plays a major role in health and disease. When the normal composition of the microbiome is thrown off balance, researchers say, the human host can get into serious trouble—especially because the 5 million to 8 million different microbial genes in our bodies vastly outnumber the 20,000 or so human genes. Indeed, recent research has implicated microbiome imbalances in disorders as diverse as cancer, obesity, inflammatory bowel disease, psoriasis, asthma, and possibly even autism.

Archaeologists Say the ‘Anthropocene’ Is Here—But It Began Long Ago

A vocal group of geologists and other scientists are pushing to define a new geological epoch, marked by climatic and environmental change caused by humans. At the Society for American Archaeology meetings in Honolulu, archaeologists argued that it9s high time for their field, which studies humans and their activities over geological time, to have a greater voice in the debate. The archaeologists agreed that human impacts on the Earth are dramatic enough to merit a new epoch name—but they also argued that such an epoch should start thousands of years ago, rather than focusing on a relatively sudden planetwide change.

CHILDREN BECOME THE FIRST VICTIMS OF FALLOUT

Paris--The most pronounced health impact on the general population of exposure to radiation from the Chernobyl accident is a sharp increase in childhood thyroid cancer in the most contaminated regions. The increase surprised many researchers because it began earlier and was much larger than expected. This has led some researchers to wonder whether some groups in the exposed population are genetically susceptible to radiation damage.

HIV's Other Immune-System Targets: Macrophages

Varenna, Italy—Last month, more than 100 AIDS experts gathered here to contemplate a major unsolved riddle of HIV infection: What role do immune-system cells other than T lymphocytes play in the progression of the disease? Researchers reported that macrophages and dendritic cells may be an important site of virus production and may also be HIVs gateway to the brain, an accomplice in the killing of T cells, and the refuge of HIV strains with different susceptibilities to antiviral drugs.

Of Two Minds About Toba's Impact

About 74,000 years ago, Mount Toba on the Indonesian island of Sumatra erupted in the most cataclysmic volcanic event of the past 2 million years. How did this gigantic eruption affect modern humans? Was Homo sapiens even in Asia at the time? At a meeting last month on the impact of the Toba eruption, some archaeologists argued that modern humans had reached India by the time the volcano blew and that their populations made it through the eruption relatively unscathed.

Clothes Make the (Hu) Man

The first clothes, worn at least 70,000 years ago and perhaps much earlier, were probably made of animal skins and helped protect early humans from the ice ages. Then at some point people learned to weave plant fibers into textiles. But when? The answer is not certain, because cloth is rarely preserved at archaeological sites. Now discoveries at a cave in the Republic of Georgia, reported on page 1359 of this week9s issue of Science, suggest that this skill was acquired more than 30,000 years ago.

Chernobyl's Thyroid Cancer Toll

Geneva—Radiation scientists now accept that the large increase in childhood thyroid cancers, particularly in Belarus and Ukraine, is the result of radiation released by the Chernobyl nuclear accident. The new focus is on trying to explain why the cancer epidemic is so virulent.

Animal Communication Helps Reveal Roots of Language

Language leaves no traces in the archaeological record, and many researchers have been doubtful about how much animal communication could reveal about the unique features of human communication. That began to change in the 1990s, when linguists, evolutionary biologists, psychologists, primatologists, and other scientists teamed up to test new hypotheses about how language arose. Since 1996, this interdisciplinary crowd has gathered every 2 years at Evolang, a meeting devoted to deciphering the evolutionary origins of language. Although some say the early Evolang gatherings suffered from too many hypotheses and too little testing, many think last month9s meeting marks a turning point for the field. Participants flocked to hear a barrage of new data from animal and human studies. The new empiricism may help resolve one of the field9s liveliest debates: whether the first human language consisted of gestures, similar to today9s sign languages, or articulated speech. At the meeting, a new and unlikely seeming animal model for human language got star billing: songbirds. Their ability to learn and imitate their parents9 melodious tunes has many parallels with the ability of human children to learn spoken language, researchers say.

On the Origin of Art and Symbolism

How and when was the artistic gift born? In the second essay in Science9s series in honor of the Year of Darwin, Michael Balter discusses the evolution of the human ability to develop mental images and convey them through abstract means such as drawing and sculpting.